Patent Application
20180366238
This patent application is also related to Patent Application Ser. No. 62/519,749 filed on Jun. 14, 2017, entitled “METHOD FOR MANUFACTURING A COMPOSITE WIRE” having Attorney Docket No. H683.158.101/P12994 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “METHOD FOR MANUFACTURING A COMPOSITE WIRE” having Attorney Docket No. H683.158.102/P12994 US01; Patent Application Ser. No. 62/519,779 filed on Jun. 14, 2017, entitled “METHOD FOR MANUFACTURING A CABLE” having Attorney Docket No. H683.159.101/P12996 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “METHOD FOR MANUFACTURING A CABLE” having Attorney Docket No. H683.159.102/P12996 US01; Patent Application Ser. No. 62/519,823 filed on Jun. 14, 2017, entitled “METHOD FOR MANUFACTURING A PASSIVATED PRODUCT” having Attorney Docket No. H683.160.101/P12998 US; patent application Ser. No. ______ filed on Jun. 4, 2018, entitled “METHOD FOR MANUFACTURING A PASSIVATED PRODUCT” having Attorney Docket No. H683.160.102/P12998 US01; Patent Application Ser. No. 62/269,268 filed on Dec. 18, 2015, entitled “ALLOY COMPRISING CR, NI, MO AND CO FOR USE IN MEDICAL DEVICES” having Attorney Docket No. H685.104.101/HU12121US PR; and patent application Ser. No. 15/382,294 filed on Dec. 16, 2016, entitled “CR, NI, MO AND CO ALLOY FOR USE IN MEDICAL DEVICES” having Attorney Docket No. H685.104.102/HU12121US.
One aspect generally relates to a composite wire, a coil comprising at least two composite wires, a cable including at least three composite wires, a medical device including such composite wire, coil and/or cable and a manufacturing method for a composite wire. The composite wire includes a first part and a second part. The first part is a metallic component. The second part includes an alloy of Cr, Ni, Mo and Co, with tightly controlled levels of impurities.
Much investigation in recent years has been directed to a search for new high-performance alloys, particularly for medical applications where a very high value is placed on reliability and materials are required which exhibit a low failure rate even over a long time period.
Cardiac Pacemakers, Implantable Cardioverter Defibrillation Devices and Cardiac Resynchronisation Devices are applications where reliability is particularly important, especially in terms of resistance to physical fatigue and to chemical corrosion. Invasive surgery is required to implant a pacemaker into the body or remove or replace parts, and it is highly desirable for the individual components of the pacemaker to have a long working life in order to reduce the requirement for surgical intervention. Furthermore, it is desirable for the working life to have a low variance. In a heart pacemaker, one component, which is exposed to a particularly high amount of stress during normal operation is the so called lead which connects the implantable pulse generator to the heart tissue. A flexible lead is required in order to connect the implantable pulse generator to the heart tissue without imposing undue physical stress on the heart and the lead flexes during normal operation, typically repetitively with a frequency on the order of that of a human heart beat. A high resistance to fatigue is therefore required in the lead in order to withstand frequent physical stress over a long period of time. A high resistance of the lead to corrosion is important not only in terms of the lifetime of the component, but also in terms of reducing toxicity to the body.
WO 2005026399 A1 discusses an approach to improving the properties of an alloy by reducing the content of titanium nitride and mixed metal carbonitride.
US 2005/0051243 A1 focuses on alloys with a reduced content of nitrogen.
Implanted medical leads and wires require material that is of sufficient fatigue resistance and electrical conductivity. In many applications, such as those for implant into the brain or where the wire material is in direct contact with the body to electrically shock or stimulate tissue, further increased fatigue resistance and electrical conductivity properties are needed.
For these and other reasons, a need exists for the present invention.
The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification, and which are not to be considered as limiting the scope. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
It is to be understood that the features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise.
One aspect provides an improved composite wire, which has, for example, improved fatigue resistance and electrical conductivity properties.
Embodiments described in the following apply also to the composite wire, the coil comprising at least two composite wires, the cable comprising at least three composite wires, the medical device comprising such composite wire, coil and/or cable and the manufacturing method for a composite wire.
In one embodiment, a composite wire is presented. The composite wire includes a first part and a second part. The first part is a metallic component.
The second part includes an alloy comprising the following alloy components:
a) Cr in the range from about 10 to about 30 wt. %;
b) Ni in the range from about 20 to about 50 wt. %;
c) Mo in the range from about 2 to about 20 wt. %;
d) Co in the range from about 10 to about 50 wt. %.
The Al content of the Cr, Ni, Mo and Co alloy is less than about 0.01 wt. % and each wt. % is based on the total weight of the alloy.
The wire may be a single strand or rod of metal or may include a bundle of such strands or rods. The wire may be configured to bear mechanical loads or electricity and/or telecommunications signals. The wire may be flexible and may be circular in cross-section or square, hexagonal, flattened, rectangular or the like.
A composite wire may include at least two different materials.
The first part may be a metal or an alloy and may provide or enhance an electrical conductivity of the composite wire.
The second part includes above mentioned alloy, which is a Cr, Ni, Mo and Co alloy. The Cr, Ni, Mo and Co alloy may be cleaner with less impurities and less and smaller inclusions which may lead to an improved resistance to physical fatigue. The Cr, Ni, Mo and Co alloy may therefore have an improved resistance to physical fatigue, a high corrosion resistance and/or the ability to be drawn into a thin wire. In an example, the Cr, Ni, Mo and Co components are major constituents of the Cr, Ni, Mo and Co alloy with at least about 95 wt. % of the alloy being Cr, Ni, Mo and Co. Details in view of the alloy are provided further below.
The composite wire according to one embodiment combines a first metallic part with a second part of a high purity Cr, Ni, Mo and Co alloy. The first metallic part provides electrical conductivity and the Cr, Ni, Mo and Co alloy and, for example, its high purity, provides an excellent fatigue resistance. As a result, the composite wire meets at the same time electrical conductivity and fatigue resistance requirements for use in highly sensitive implanted applications such as the human brain or other applications where direct and prolonged contact with the body is required, such as in sensing and stimulation applications.
In an example, the first part at least partially surrounds the second part when seen in a cross section. The first part may also essentially or completely surround the second part when seen in a cross section. The first part may be a clad, cover, coating or the like. In an example, the first part is biocompatible. Consequently, the first part may provide a biocompatible clad to the composite wire and thereby greatly improve its biocompatibility. The first part may also or additionally be corrosion resistant, which not only avoids corrosion, but also the occurrence of corrosion products and their cytotoxicity. As a result, also the biostability of the composite wire may be greatly improved. Increased biocompatibility and/or biostability may be considerably important for implants into the brain or into other locations where the composite wire is in direct and prolonged contact with the body to, for example, electrically shock or stimulate tissue.
In an example, the first part includes at least one of a group of Platinum, a Platinum based alloy, a Platinum-Iridium alloy, a Platinum-Tungsten alloy, Gold, a Gold alloy, Tantalum, Titanium, a Titanium-Molybdenum alloy, a Titanium Aluminum Vanadium alloy and the like. In an example, the first part includes a Platinum-Iridium alloy with about 70-90 wt. % Platinum and 10-30 wt. % Iridium. Such composition and Platinum and Platinum based alloys in general may enhance the biocompatibility and/or biostability of the composite wire for use as e.g. a chronic implant.
In an example, the composite wire further includes a core part, which is at least partially surrounded by the second part when seen in a cross section. The core part may also be essentially or completely surrounded by the second part when seen in a cross section. In an example, the core part is a metallic component. In an example, the core part is electrically conductive. In an example, the core part includes at least one of a group of Silver, Platinum and the like. The core part may further improve the electrical properties and, for example, the electrical conductivity of the composite wire. A core content of a composite wire may be in the range from 15 to 50 wt. %, in one embodiment, in the range from 17.5 to 45.7 wt. %, and in one embodiment, in the range from 28.7 to 37.7 wt. % based on the total weight of the wire.
As described above, the first part may form an outer shell for the second part comprising the Cr, Ni, Mo and Co alloy. As described below, the second part comprising the Cr, Ni, Mo and Co alloy may also form an outer shell for the first part.
In another example, the second part at least partially surrounds the first part when seen in a cross section. The second part may also essentially or completely surround the first part when seen in a cross section. In an example, the first part is a filling material and includes at least one of a group of Platinum, Tantalum, Gold, Copper, Silver and alloys thereof. In another example, the first part is not pure Silver. It may be a Silver alloy such as, for example, AgMg1. For example, Platinum and Platinum based alloys may enhance biocompatibility of the composite wire. Filling materials such as Ta, Pt, Au, Cu provide or increase radiopacity, electrical conductivity and/or a melting temperature (e.g. AgMg-core compared to pure Ag).
In an example, a filling degree of the filling material or first part relative to the Cr, Ni, Mo and Co alloy or second part is in the range from 15% to 41%, in one embodiment, in the range from 20% to 35%, and, in one embodiment, in the range from 23% to 33% when seen in a cross section.
In an example, the composite wire further includes a circumference part, which at least partially surrounds the second part when seen in a cross section. The circumference part may also essentially or completely surround the second part when seen in a cross section. In an example, the circumference part is biocompatible. In an example, the circumference part includes at least one of a group of Platinum, a Platinum based alloy, a Platinum-Iridium alloy, a Platinum-Tungsten alloy, Gold, a Gold alloy, Tantalum, Titanium, a Titanium-Molybdenum alloy, a Titanium Aluminum Vanadium alloy and the like. For example, Platinum and Platinum based alloys may enhance biocompatibility of the composite wire.
In an example, a diameter of the composite wire is in a range of 5 to 500 μm, in one embodiment, in the range of 10 to 250 □m, and, in one embodiment, in the range of 15 to 35 □m. The diameter of the composite wire used in medical applications could range from 0.0004″ to 0.020″, more commonly from 0.0007″ to 0.010″.
In an example, the composite wire further includes a coating as outermost part at least partially surrounding all other parts. The coating may also essentially or completely surround all other parts. The coating may be applied independent of the structure and materials of the composite wire. In other words, the coating may be applied on the first part, the second part or the circumference part, whichever part is the outermost part of the composite wire. The coating may also be applied on the composite wire in straight or coiled condition, on several composite wires later on forming a cable or strand, or the cable or the strand itself, which includes several composite wires.
In an example, the coating provides or enhances electrical insulation, electrical conductivity, mechanical properties, lubricity, biocompatibility and/or biostability of the composite wire. In an example, the coating includes a polymer or other organic based coating. The coating may be a solvent based and cured polymer. The coating may be soluble in organic solvents, water and/or mixtures thereof. The coating may include at least one of a group of ETFE, PFA, Polyimide, Polyamide, PTFE, Polyurethane, PEEK, Parylene or the like. The coating may include Iridium Oxide, Titanium Nitride or the like.
In an example, the coating provides or enhances electrical insulation, for example, for conductor applications. The coating may then include at least a non-conductive polymer, a ceramic and/or a cermet. The coating may also include at least one of a group of diamond-like carbon, carbon nanotube, graphite, other carbon-based coatings or the like.
In another example, the coating provides or enhances electrical conductivity and/or reduces resistance and/or impedance. The coating may then include at least a conductive polymer. In an example, the coating includes at least one of a group of PEDOT, PEDOT:PSS or the like.
In an example, the coating provides or enhances (long-term) biostability in the body and/or charge capacitance for improved contact to tissue and/or other biological properties. The coating may then include at least one of a group of enzymes, antimicrobials, steroids, other drugs or biological active substances or the like. The coating may also reduce body tissue inflammatory response or damage from the implanted composite wire.
A thickness of the coating may range from a nanometer scale to millimeter scale depending on the application. Biological and conductive coatings may be on a smaller nano or micro scale, whereas insulative coatings may range from 1 μm to 100 μm. The thickness of the coating may range from 5 to 50 □m, in one embodiment, from 10 to 20 □m.
The coating materials can be applied continuously by, for example, thermoplastic polymer extrusion, dip coating or enameling processes.
The composite wires as described above can be formed into coils or cables for use in medical lead applications such as pacemaker leads and neurostimulation leads. In the coil form, the coil can include a single wire or multiple wires. The multiple wires can include a single conductor path or be electrically insulated to include multiple separate electrical paths. In the cable configuration, the cable may include multiple wires twisted together in various configurations in order to improve flexibility of the overall strand. Likewise, the cable can include a single electrical path or multiple groups of wires, each electrically isolated by insulator coatings. The cables may then be used in a straight configuration or can be further wound into a coil form similar as described above.
According to one embodiment, a coil comprising at least two composite wires as described above is presented, wherein the at least two composite wires are wound or coiled together.
Possible coil configurations (but not limited to) are single or multi-filar coils (up to 8 wires forming one coil). They can be tight wound with no gap between coiled wires or open wound with a gap of e.g. 5 to 50 μm between wires. The coils may have outer diameters of 50 μm to 3 mm. In an example, the coil includes 1 to 16 composite wires wound in 1 to 3 concentric sub coils. In one embodiment, 1 to 8 composite wires are wound in one individual coil. In an example, at least some of the composite wires are electrically insulated from each other.
In an example, a diameter of a composite wire in a coil is in a range of 50 to 250 μm, in one embodiment, in a range of 100 to 200 □m.
According to one embodiment, also a cable comprising at least three composite wires as described above is presented, wherein the at least three composite wires are stranded together.
Possible cable configurations (but not limited to) are 1×3, 3×3, 3×3×3, 3×7, 7×3, 3×19, 19×3, 19×7, 7×19, 7×7×7, 7×7, 1×7, 1×19 and the like. In an example, the cable includes 3 to 361 composite wires stranded together. In an example, the at least some of the composite wires are electrically insulated from each other. In one embodiment, 3 to 133 wires and in one embodiment, 7 to 49 wires are stranded together into one cable.
In an example, a diameter of a composite wire in a cable is in a range of 5 to 50 μm, in one embodiment, in a range of 15 to 35 □m.
The wires, coils and cables may be coated with polymers to provide electrical insulation, and used in this form or can be then stranded into multi-conductor cables or coiled into multi-conductor coils. The wires, coils or cables may be used as conductor paths in medical device products. Such conductor paths may be used in leads for sensing or delivering cardiac therapies such as pacing, defibrillating, or cardiac resynchronization, or in leads for sensing or delivering stimulation to nerves or neural tissue in areas such as deep brain, spinal cord, vagus nerve, and peripheral nerves.
According to one embodiment, a medical device comprising at least one of the group of a composite wire, a coil and a cable as described above is presented, wherein the at least one composite wire, coil and/or cable is used as a lead. In an example, the lead is configured for at least one of a group of: pacing, defibrillating, cardiac rhythm management, resynchronization and/or stimulation to nerves or neural tissue in deep brain, spinal cord, vagus nerve or a peripheral nerve and the like. In an example, the medical device may be a pacemaker, an implantable cardioverter defibrillator, a cardiac resynchronization device, a neuromodulation device, a cochlea implant or any other implantable stimulation device comprising a composite wire as described above as a lead.
The lead of the medical device may include several composite wires (for example, with a Ta core and a Pt clad on the outside), in one embodiment grouped into two or more cables, each cable comprising two or more composite wires. In one embodiment, the cables have a thickness in the range from 0.05 to about 0.5 mm, in one embodiment, in the range from about 0.1 to 0.4 mm.
According to one embodiment, a manufacturing method for a composite wire is presented. The manufacturing method for a composite wire includes the following steps, not necessarily in this order:
The first part is a metallic component. The second part includes an alloy comprising the following alloy components:
a) Cr in the range from about 10 to about 30 wt. %;
b) Ni in the range from about 20 to about 50 wt. %;
c) Mo in the range from about 2 to about 20 wt. %;
d) Co in the range from about 10 to about 50 wt. %.
The Al content of the Cr, Ni, Mo and Co alloy is less than about 0.01 wt. % and each wt. % is based on the total weight of the alloy.
In an example, the composite wire may be produced in that the material undergoes a joining process into a single cylinder or rod of material that includes the at least two concentric parts and materials. Such process can involve joining rods and cylinders of material into a single cylinder comprising the desired materials and cross-section ratios of the materials. A single cylinder may or may not be further jacketed for protection, and then extruded, swaged, or drawn through a series of dies to reduce its diameter. This process may be repeated with multiple reduction and heat treatment steps in order to reduce the composite wire diameter to desired diameter and mechanical properties. Of course, also a third or even more materials may be included as three or more concentric parts and materials in the above described joining process into a single cylinder or rod of material.
In an example, the Cr, Ni, Mo and Co alloy is molten, forged and rolled to bar sizes of ˜1-1.5″, surface peeled, shaved or ground, and gun-drilled to create a hollow for tube drawing. A tube processing may include multiple steps of drawing, cleaning and annealing to create smaller tube outer diameters of 0.1-0.3″. The tube may be filled with a core material in form of a rod slightly smaller than the outer diameter of the tube. The filled tube may be drawn through, for example, diamond dies to close a gap between a core material and an outer oy material. This composite wire can then be used as second core to fill an, for example, Pt or Pt-alloy tube which forms an outermost layer and coating of a coated composite wire. The coated composite wire can then be drawn to smaller sizes using, for example, a mineral drawing oil and diamond dies. Down to small sizes, the coated composite wire may have to be (in-line) annealed one or multiple times to soften the material for further drawing.
The Cr, Ni, Mo and Co alloy may be an alloy, which has improved resistance to physical fatigue, a high corrosion resistance, and/or which can be drawn into a thin wire, in one embodiment, less than about 50 μm. The wire according to one embodiment, may be a wire having comparable tensile properties to known wires, but for which the proportion of outlying failures in fatigue resistance is reduced.
A contribution to achieving at least one of the above described objects is made by the following embodiments of the Cr, Ni, Mo and Co alloy (in the following “alloy”).
|1| An alloy comprising the following alloy components:
|2| The alloy according to embodiment |1|, wherein the content of Mg is less than about 0.005 wt. %, in one embodiment, less than about 0.0001 wt. %, in one embodiment, less than about 0.00001 wt. %, based on the total weight of the alloy.
|3| The alloy according to embodiment |1| or |2|, wherein the content of Ca is less than about 0.005 wt. %, in one embodiment, less than about 0.0001 wt. % in one embodiment, less than about 0.00001 wt. %, based on the total weight of the alloy.
|4| The alloy according to any of the preceding embodiments, wherein the content of Ce is less than about 0.005 wt. %, in one embodiment, less than about 0.0001 wt. % in one embodiment, less than about 0.00001 wt. %, based on the total weight of the alloy.
|5| The alloy according to any of the preceding embodiments, wherein the content of Ti is less than about 0.1 wt. %, in one embodiment, less than about 0.01 wt. % in one embodiment, less than about 0.001 wt. %, further in one embodiment, less than about 0.0005 wt. %, based on the total weight of the alloy.
|6| The alloy according to any of the preceding embodiments, wherein the content of Fe is in the range from about 0.0001 to about 1 wt. %, in one embodiment, in the range from about 0.0005 to about 0.1 wt. %, in one embodiment, in the range from about 0.001 to about 0.05 wt. %, based on the total weight of the alloy.
|7| The alloy according to any of the preceding embodiments, wherein at least one of the following is satisfied:
|8| The alloy according to any of the preceding embodiments, wherein at least one of the following is satisfied:
|9| The alloy according to any of the preceding embodiments, wherein at least one of the following is satisfied:
|10| The alloy according to any of the preceding embodiments, wherein at least one of the following is satisfied:
In aspects of this embodiment, the combination of the above criteria which are satisfied is selected from the group consisting of: a), b), c), d), a)+b), a)+c), a)+d), b)+c), b)+d), c)+d), a)+b)+c), a)+b)+d), a)+c)+d), b)+c)+d), a)+b)+c)+d), e), a)+e), b)+e), c)+e), d)+e), a)+b)+e), a)+c)+e), a)+d)+e), b)+c)+e), b)+d)+e), c)+d)+e), a)+b)+c)+e), a)+b)+d)+e), a)+c)+d)+e), b)+c)+d)+e) and a)+b)+c)+d)+e).
|11| A process for the preparation of an alloy comprising the following preparation steps:
|12| The process according to embodiment |11|, wherein pressure in step b) is below about 0.1 bar, in one embodiment, below about 0.05 bar, in one embodiment, below about 0.01 bar.
|13| The process according to embodiment |11| or |12|, wherein the leak rate in step b) is below about 0.1 bar/min, in one embodiment, below about 0.05 bar/min, in one embodiment, below about 0.01 bar/min.
|14| The process according to any of the embodiments |11| to |13|, wherein the pressure in step d) is below about 0.05 bar, in one embodiment, below about 0.01 bar, in one embodiment, below about 0.005 bar.
|15| The process according to any of the embodiments |11| to |14|, wherein the leak rate in step d) is below about 0.05 bar/min, in one embodiment, less than about 0.01 bar/min, more in one embodiment, less than about 0.005 bar/min.
|16| The process according to any of the embodiments |11| to |15|, further comprising a homogenisation step carried out at a temperature in the range from about 900 to about 1300° C., in one embodiment, in the range from about 1000 to about 1250° C., in one embodiment, in the range from about 1100 to about 1225° C.
|17| The process according to any of the embodiments |11| to |16|, further comprising a cogging step carried out at a temperature in the range from about 900 to about 1300° C., in one embodiment, in the range from about 1000 to about 1250° C., in one embodiment, in the range from about 1100 to about 1225° C.
|18| The process according to any of the embodiments |11| to |17|, further comprising a finish roll step carried out at a temperature in the range from about 900 to about 1300° C., in one embodiment, in the range from about 1000 to about 1250° C., in one embodiment, in the range from about 1100 to about 1225° C.
|19| The process according to any of the embodiments |11| to |18|, further comprising a straightening step. In one aspect of this embodiment, the straightening is a hot straightening, in one embodiment, carried out at a temperature in the range from about 900 to about 1200° C., in one embodiment, in the range from about 950 to about 1100° C., in one embodiment, in the range from about 1000 to about 1075° C. In one aspect of this embodiment, the straightening is a cold straightening, in one embodiment, carried out at ambient temperature, in one embodiment, at a temperature in the range from about 10 to about 100° C., in one embodiment, in the range from about 15 to about 80° C., in one embodiment, in the range from about 20 to about 50° C. |20| An alloy obtainable by a process according to any of the embodiments |11| to |19|.
|21| An electrical wire comprising an alloy according to any of the embodiments |1| to |10| or |20|.
|22| A medical device comprising a wire according to embodiment |21|.
|23| A pacemaker, an implantable cardioverter defibrillator, a cardiac resynchronization device, a neuromodulation device, a cochlea implant or any other implantable stimulation device comprising a wire according to embodiment |21|.
The Cr, Ni, Mo and Co alloy include two or more elements, in one embodiment, as a solid mixture, in one embodiment, with an enthalpy of mixing of the constituent elements of less than about 10 KJ/mol, in one embodiment, less than about 5 KJ/mol, in one embodiment, less than about 1 KJ/mol. The Cr, Ni, Mo and Co alloy include Cr, Ni, Mo and Co as major constituents, in one embodiment, with at least about 95 wt. %, in one embodiment, at least about 99 wt. %, further in one embodiment, at least about 99.9 wt. %, in one embodiment, at least about 99.95 wt. % of the alloy being Cr, Ni, Mo and Co.
A composition of the Cr, Ni, Mo and Co alloy is in one embodiment, which improves favorable properties of the alloy, for example, resistance to fatigue and/or corrosion resistance, or both.
In one embodiment, the properties of the alloy are improved by limiting the content of impurities or limiting the content of a combination of different impurities, according the embodiments.
In one embodiment, there is a low, in one embodiment, zero, concentration of inclusions in the alloy. In one embodiment, this is achieved by limiting the content of impurities. In one embodiment, the alloy contains less than about 0.01%, in one embodiment, less than about 0.005%, in one embodiment, less than about 0.001% inclusions. The % of inclusions is, in one embodiment, determined using the microscopic inspection method given in the test methods. Content of inclusions as % is there determined as the proportion of the cross sectional area of the sample surface made up of inclusions. In some instances, the alloy includes a low, in one embodiment, a zero concentration of inorganic non-metallic solid inclusions, in one embodiment, of inorganic oxide inclusions. Inorganic oxides in this context can refer to metal oxides, non-metal oxides and metalloid-oxides. In some cases the alloy includes a low, in one embodiment, a zero concentration of inclusions comprising one or more selected from the group consisting of: Si, Al, Ti, Zr and B; in one embodiment, selected form the group consisting of: Si Ti, and Al.
In one embodiment, one or more treating material(s) is/are contacted with the mixture of the process in order to remove oxygen from the mixture of the process, in one embodiment, by incorporation of the oxygen into a dross and removal of the dross. In one embodiment, treating materials in this context include one or more selected from the list consisting of: Al, Mg, Ca and Ce; in one embodiment, in the form of an element and/or in the form of an alloy, wherein the alloy in one embodiment, contains a further metal being selected from group consisting of Cr, Ni, Mo and Co or at least two thereof, in one embodiment, Ni.
In one embodiment, in order to achieve the concentrations of constituents of the alloy, described above in the embodiments, the skilled person may vary the proportions of starting materials employed in the preparation process. The proportions of the starting materials might not be equal to the proportions of constituents of the product, due to net loss or gain during the preparation process.
The process for the preparation of the alloy in one embodiment, includes the following steps:
In one embodiment, the process includes two or more vacuum induction melting steps. In another embodiment, the process includes two or more vacuum melting steps. In another embodiment, the process includes two or more vacuum induction melting steps and two or more vacuum arc melting steps.
In one embodiment, the process further includes one or more of the following steps:
In various embodiments, the process includes a combination of the above steps selected from the list consisting of: c), d), e), f), g), c)+d), c)+e), c)+f), c)+g), d)+e), d)+f), d)+g), e)+f), e)+g), f)+g), c)+d)+e), c)+d)+f), c)+d)+g), c)+e)+f), c)+e)+g), c)+f)+g), d)+e)+f), d)+e)+g), d)+f)+g), e)+f)+g), d)+e)+f)+g), c)+e)+f)+g), c)+d)+f)+g), c)+d)+e)+g), c)+d)+e)+f) and c)+d)+e)+f)+g).
In one embodiment, one or more of the steps c)-g) is carried out two or more times.
In one embodiment of vacuum induction melting steps, a material is heated by inducing an electric current in the material, in one embodiment, by electromagnetic induction. The pressure in the vacuum induction melting step is in one embodiment, below about 0.1 mbar, in one embodiment, below about 0.01 mbar, in one embodiment, below about 0.001 mbar. The vacuum induction melt step is, in one embodiment, carried out in an oven, in one embodiment, with a low leak rate, in one embodiment, below about 0.1 mbar·l/s, in one embodiment, below about 0.01 mbar·l/s, in one embodiment, below about 0.001 mbar·l/s. The leak rate is in one embodiment, tested before the vacuum induction melting step by evacuating the oven, closing the valves of the oven, and measuring the rate of increase of pressure in the oven.
In one embodiment, the vacuum induction melting step is carried out in an inert atmosphere, in one embodiment, argon, in one embodiment, an atmosphere comprising at least about 90 wt. %, in one embodiment, at least about 99 wt. %, in one embodiment, at least about 99.9 wt. % of inert gas, in one embodiment, argon. In one aspect of this embodiment, the oven is evacuated and inert gas, in one embodiment, argon, introduced into the oven before melting. In one aspect of this embodiment, the pressure in the vacuum induction melting step is in the range from about 1 to about 200 mbar, in one embodiment, in the arrange from about 10 to about 150 mbar, in one embodiment, in the range from about 20 to about 100 mbar.
In one embodiment, the vacuum arc melting steps, a material is heated by passing an electrical current through the material, in one embodiment, with an electrical power in the range from about 300 to about 1200 W/kg, in one embodiment, in the range from about 400 to about 1000 W/kg, in one embodiment, in the range from about 450 to about 900 W/kg, based on the mass of material heated. The pressure in the vacuum arc melting step is in one embodiment, below about 0.1 mbar, in one embodiment, below about 0.01 mbar, in one embodiment, below about 0.001 mbar. The vacuum arc melt step is in one embodiment, carried out in an oven, in one embodiment, with a low leak rate, in one embodiment, below about 0.1 mbar·l/s, in one embodiment, below about 0.05 mbar·l/s, in one embodiment, below about 0.01 mbar·l/s. The leak rate is in one embodiment, tested before the vacuum arc melting step by evacuating the oven, closing the valves of the oven, and measuring the rate of increase of pressure in the oven. In one embodiment, the vacuum arc melting step is carried out in an inert atmosphere, in one embodiment, argon, in one embodiment, an atmosphere comprising at least about 90 wt. %, in one embodiment, at least about 99 wt. %, in one embodiment, at least about 99.9 wt. % of inert gas, in one embodiment, argon. In one aspect of this embodiment, the oven is evacuated and inert gas, in one embodiment, argon, introduced into the oven before melting. In one aspect of this embodiment, the pressure in the vacuum arc melting step is in the range from about 0.001 to about 0.2 bar, in one embodiment, in the range from about 0.01 to about 0.15 bar, in one embodiment, in the range from about 0.05 to about 0.1 bar.
Homogenisation steps according to one embodiment allow reduction of inhomogeneity in a material, in one embodiment, by heating. In one embodiment, a material is heated to a temperature which is below its melting temperature, in one embodiment, below its incipient melting temperature. In one embodiment, the material is homogenised for a duration in the range from about 10 min. to about 20 hours, in one embodiment, in the range from about 3 hours to about 10 hours, in one embodiment, in the range from about 5 hours to about 8 hours. Homogenisation is in one embodiment, carried out in a vacuum or in a gaseous atmosphere, in one embodiment, in a gaseous atmosphere. In one embodiment, the homogenisation step is carried out close to atmospheric pressure, in one embodiment, in the range from about 0.5 to about 1.5 bar, in one embodiment, in the range from about 0.8 to about 1.2 bar, in one embodiment, in the range from about 0.9 to about 1.1 bar. In one embodiment, the homogenisation step is carried out in air.
In cogging steps according to one embodiment, the porosity or grain size or both of a material are reduced, in one embodiment, at elevated temperatures, in one embodiment, below the melting point of the material, in one embodiment, with the application of compressive force. Compressive forces may be applied locally or in a delocalised manner, in one embodiment, by one or more selected from the group consisting of: rolling, pressing, beating and turning. Where the material to be cogged has a mass below about 10 kg, in one embodiment, below about 8 kg, in one embodiment, below about 5 kg, rolling is done. Where the material to be cogged has a mass above about 10 kg, in one embodiment, above about 20 kg, in one embodiment, above about 30 kg, beating or turning is done. In one embodiment, the smallest dimension of the material is reduced during the cogging process.
Finish roll steps according to one embodiment reduce the smallest dimension of the material, in one embodiment, by passing the material through one or more pairs of rolls, in one embodiment, below the melting point of the material, in one embodiment, below its incipient melting point. In one embodiment, the finish roll step reduces the porosity or grain size of the material, or, both.
Straightening in one embodiment, reduces the physical curvature of the material, in one embodiment, so as to facilitate further grinding or machining steps. Straightening is in one embodiment, carried out by applying compressive force. The straightening step is in one embodiment, carried out below the melting point of the material, in one embodiment, below its incipient melting point. In one embodiment, the process includes a hot straightening step. In one embodiment, the process includes a cold straightening step, in one embodiment, carried out at around ambient temperature. Cold straightening is in one embodiment, carried out at a temperature in the range from about 10 to about 100° C., in one embodiment, in the range from about 15 to about 80° C., in one embodiment, in the range from about 20 to about 50° C.
In this text, reference is made variously to a coated or cladded wire, which includes a wire core and a shell. The shell might be coated or cladded onto the core wire.
A lead according to one embodiment includes at least one proximal connector, at least one distal electrode and a flexible elongated conductor that is electrically connecting the electrode(s) to the connector(s). In one embodiment, the elongated conductor is a coiled wire or a cable and includes the alloy according to one embodiment.
A contribution to achieving at least one of the above mentioned objects is made by a wire comprising an alloy according to one embodiment, in one embodiment, having a thickness in the range from about 10 to about 50 μm, in one embodiment, in the range from about 15 to about 35 μm. In one embodiment, the wire further includes silver metal.
The lead includes a silver core and an alloy according to one embodiment, in one embodiment, present as a shell surrounding the silver core.
A contribution to achieving at least one of the above mentioned objects is made by a lead comprising one or more wires according to one embodiment, in one embodiment, grouped into two or more cables, each cable comprising two or more wires according to one embodiment. In one embodiment, the cables have a thickness in the range from about 0.05 to about 0.5 mm, in one embodiment, in the range from about 0.1 to 0.4 mm.
A contribution to achieving at least one of the above mentioned problems is made by a medical device, in one embodiment, a pacemaker, comprising a lead according to one embodiment. In one embodiment, a pacemaker includes:
One or more leads.
In one embodiment, the pacemaker includes one or more pulsers.
In one embodiment, the pacemaker includes one or more energy cells, in one embodiment, one or more electrical cells.
A process for the preparation of a wire includes the steps:
In one embodiment, the Ag content of the wire obtainable by the process is in the range from about 15 to about 50 wt. %, in one embodiment, in the range from about 17.5 to about 45.7 wt. %, in one embodiment, in the range from about 28.7 to about 37.7 wt. %, based on the total weight of the wire.
In one embodiment, the diameter of the wire obtainable by the process is in the range from about 5 to about 50 μm, in one embodiment, in the range from about 15 to about 35 μm.
In one embodiment, the filling degree of silver in the wire obtainable by the process is in the range from about 15% to about 41%, in one embodiment, in the range from about 20% to about 35%, in one embodiment, in the range from about 23% to about 33%.
It shall be understood that the composite wire, the coil comprising at least two composite wires, the cable comprising at least three composite wires, the medical device comprising such composite wire, coil and/or cable and the manufacturing method for a composite wire according to the independent claims have similar and/or identical embodiments, for example, as defined in the dependent claims. It shall be understood further that an embodiment can also be any combination of the dependent claims with the respective independent claim.
These and other aspects will become apparent from and be elucidated with reference to the embodiments described hereinafter.
In
The second part 30 includes above mentioned Cr, Ni, Mo and Co alloy. The Cr, Ni, Mo and Co alloy is cleaner with less impurities and less and smaller inclusions which leads to an improved resistance to physical fatigue.
The composite wire 10 according to one embodiment combines the first metallic part with the second part 30 of a high purity Cr, Ni, Mo and Co alloy. The first metallic part provides electrical conductivity and the Cr, Ni, Mo and Co alloy and, for example, its high purity, provides an excellent fatigue resistance. As a result, the composite wire 10 meets at the same time electrical conductivity and fatigue resistance requirements for use in highly sensitive implanted applications such as the human brain.
As illustrated in
As described above, the first part 20 forms an outer shell for the second part 30 comprising the Cr, Ni, Mo and Co alloy. As described below, the second part 30 comprising the Cr, Ni, Mo and Co alloy may also form an outer shell for the first part 20.
In
As illustrated in
All composite wires 10 according to embodiments may further include a coating (not illustrated) as outermost part surrounding all other parts. The coating may be applied on the first part 20, the second part 30 or the circumference part 80, whichever part is the outermost part of the composite wire 10. The coating may provide or enhance electrical insulation, electrical conductivity, mechanical properties, lubricity, biocompatibility and/or biostability of the composite wire 10.
The composite wires 10 as described above can be formed into coils or cables for use in medical lead applications such as pacemaker leads and neurostimulation leads.
For a quantitative chemical analysis of the alloy, the following methods are used:
a) the main components of the alloy (Co, Cr, Ni, Mo) are measured by X-ray fluorescence XRF using the XRF Lab Report—S8 TIGER from the company BRUKER (Bruker AXS GmbH Östliche Rheinbrückenstr. 49, 76187 Karlsruhe, Germany)
b) Trace elements present in the alloy (Mn, P, Si, Fe, Ti, Al, B, Mg, Ca, Ce, Ti) are measured by glow discharge mass spectrometry (GDMS) using the ASTRUM from Nu Instruments (Nu Instruments Limited, Unit 74, Clywedog Road South, Wrexham, LL13 9XS UK.)
c) Gas or non-metallic components in the alloy (H, O, C, N, S) are measured by carrier-gas hot extraction using the ONH836 from LECO (LECO Corporation, 3000 Lakeview Avenue, St. Joseph, Mich. 49085)
The leak rate of the furnace chamber is measured using the following procedure:
The Vacuum furnace chamber is evacuated to the required pressure by a vacuum pumping station. When the required pressure is reached, the pressure valve between the vacuum furnace chamber and the vacuum pumping station is closed. The pressure increase of the vacuum furnace chamber over a given length of time defines the leak rate of the equipment.
Rotating beam fatigue testing was carried out using Valley Instruments model #100 test machine (
Valley Instruments Wire Fatigue Tester Model #100 user manual (Valley Instruments (Division of Positool Technologies, Inc.), Brunswick, Ohio, USA. Fatigue Tester Model 100 Manual) describes that a loop, formed by an elastic length held so that the axes of the specimen at the point of retention are exactly parallel, assumes a shape in which:
(1) The length of the loop is 2.19 times the base,
(2) The height of the arch is always 0.835 times the base,
(3) The minimum radius of the curvature occurs at the apex of the arch and is exactly 0.417 times the base, and
(4) The bending stress at the point of minimum curvature bears a simple reciprocal linear relationship to any of the four physical dimensions (length, height, base, and minimum curvature).
The following formulas express the exact relationship:
C=1.198*E*d/S
h=0.835*C
L=2.19*C
R=0.417*C
P=0.141*E*d4/C2
C=chuck to bushing distance
d=diameter of wire
h=height of loop
E=modulus of elasticity
L=length of wire external to chucks
R=minimum of radius of curvature
S=bending stress
P=bushing load or lateral force at the chuck
With the above listed formula, the bending stress S (at the peak of the loop) can be calculated by the following equation:
S=1.198*E*d/C
The machine set-up involves calculating the desired sample length and center distance using the modulus of elasticity of the material and equations developed by Valley Instruments Company (user manual).
Definition: Inclusions are defined as internal flaws or contaminations (such as nitrides or oxides) within the billet or rod from which the wire or tube is produced. The transverse inclusion size is defined as the largest dimension of an internal flaw measured on transverse cross-sections of the billet, rod or wire. The longitudinal inclusion size is defined as the largest dimension of an internal flaw measured on longitudinal cross-sections of the billet, rod or wire. A cross-section diametral line is defined as any line within the cross-section having a length equal to or greater than 95% of the true cross-section diameter.
a) Sectioning
For each material lot, the billet, rod or wire is to be sectioned at each end so that there are an equal number of cross sections sampled at the one end as there are samples at the other end (number of samples taken from each end shall differ by no more than one). The total number of cross sections samples depends on the diameter of the billet, rod or wire and is specified in Table 1. The length of each cross section is to be less than its diameter.
b) Imaging
For each billet, rod or solid wire cross-section, non-overlapping images are to be taken at 500× magnification along diametral lines so that the total examined area per sample is at least 1.77 mm2. A cross-section diametral line is defined as any line within the cross-section having a length equal to or greater than 95% of the true cross-section diameter. Angular separation between two diametral lines on a cross-section shall be a minimum of 60 degrees. The number of images and the number of diametral lines depends on the diameter of the billet, rod or wire and is specified in Table 1.
The total number of images is illustrated in Table 1 and was calculated based on the number of images per sample and the number of samples.
c) Measurement
Each of the images is to be inspected to detect the presence of inclusions or strings of inclusions that exceed a size of 3.0 μm in their largest dimension. The image inspection may be accomplished either by manual examination or by automated scanning.
The test method to analyse fracture surfaces of fatigue tested samples was Scanning electron microscopy (SEM). A Zeiss Ultra 55 Gemini was used for the sample analysis of the present embodiments and comparative samples.
Two imaging modes were used to analyse and illustrate the tested samples.
a) SE: the detection of secondary electrons (SE) results in images with a well-defined, three-dimensional appearance. The surface topography can be illustrated in high resolution.
b) BSE: backscatter electrons (BSE) are used to detect contrast between areas with different chemical compositions. Heavy elements (high atomic number) backscatter electrons more strongly than light elements (low atomic number), and thus appear brighter in the image.
The MP35N heats were VIM-VAR melted, to minimize the impurity content and to obtain a sound ingot with good chemical uniformity and metallurgical properties. The chemistry of representative heats: Heat 1, Heat 2 and Heat 3 are listed in Table 3. The table also provides the chemistry of a VIM-VAR melted, commercially available MP35N alloy and for reference the chemical requirements per ASTM F562-13, a standard specification for wrought MP35N alloy. The major constituents of MP35N alloy are Co, Ni, Cr and Mo. The new alloy heats were melted in 2 steps. The first melting step was Vacuum Induction Melting (VIM). The VIM furnace consists of a water cooled vacuum melt chamber, an oxide ceramic crucible held in a cylindrical induction heating coil inside the melt chamber, an AC electric power supply, a vacuum pumping system, a raw material adding chamber and a cylindrical metal mold held below and offset from the crucible-induction coil assembly. The vacuum melt chamber, raw material adding chamber and vacuum pumping system are separated by isolation valves. The induction heating coil is water cooled. Electric current from the power supply passes through the induction heating coil creating a magnetic field inside the furnace. The magnetic field induces eddy currents inside the raw materials causing Joule heating. Joule heating raises the temperature of the raw materials to above their melting point. The magnetic field mixes the liquid raw materials to make a homogeneous alloy. The crucible is tilted to pour the liquid alloy from the crucible into the mold. The alloy cools to a solid in the mold under vacuum and is removed from the furnace. The alloy ingot is removed from the mold and it is prepared for re-melting.
For the example heats, 136 kilograms of elemental raw materials were placed in the furnace in proportions calculated to make the aim chemistry. The VIM furnace was closed and pumped down to □ 0.00001 bar. A leak-up rate was measured after reaching the desired vacuum pressure level to ensure a vacuum tight furnace. The leak-up rate was □ 0.00001 bar/min. Electric power was applied to the induction heating coil. Once the melt was in progress, the vacuum level was recorded at specified intervals to monitor the progress of melting and the mixing and reaction of all of the raw materials. When the reactions ceased as indicated by a constant vacuum pressure level, the heat was poured into a 152.4 mm diameter cylindrical mold.
Each heat was subsequently re-melted by a Vacuum Arc Re-melting (VAR) process to make a 203.2 mm diameter ingot. The VAR furnace consists of water cooled vacuum chamber, a 203.2 mm diameter water cooled copper crucible, a direct current electric power supply, a vacuum pumping system, isolation valves and a computer based electrical system to monitor and control the application of current to the electrode inside the vacuum chamber. The furnace was pumped down to □ 0.000006 bar before carrying out the leak-up rate test. A leak rate of □ 0.000006 bar/min was obtained. The electrode was moved to a close proximity to the bottom of the crucible. Electric power was applied at a level to cause an electric arc to be struck between the crucible bottom and the alloy electrode. The electric arc causes the electrode to melt and drip into the bottom of the crucible creating a liquid metal pool that solidifies as the arc moves away from the molten pool. The process was continued at a controlled rate until the electrode was consumed. The power was turned off and the ingot was cooled under vacuum. The ingot was removed from the furnace for processing to product.
The as-cast ingot was charged into a gas-fired front opening box furnace with ambient air atmosphere. The furnace was preset to a temperature of 815° C. Upon equilibration of furnace temperature, the ingot was held for additional 4 hours prior to raising the furnace temperature. The ingot was then heated to 1177° C. at a heating rate of 200 K per hour. The ingot was held for 7 hours at 1177° C. for homogenization. After homogenization, the ingot was hot rolled from 203 mm to 137 mm round cornered square (RCS) billet using a 559 mm diameter Morgenshammer Mill operating at ambient temperature. The Morgenshammer Mill is a manually operated tilt table mill with 3 high rolls allowing heavy bar to be rolled alternately between the bottom and middle roll and the top and middle roll. After hot rolling the RCS billet was air cooled, abrasively ground by hand to remove surface imperfections and cut to square the ends. The billet was reheated and hot rolled to 51 mm RCS at 1177° C. on the 559 mm Morgenshammer Mill. The RCS was cut to shorter lengths of final rolling on a hand operated 406 mm diameter Morgenshammer Mill with 3 high rolls. All bar manipulation on this mill is done by hand at floor level. The RCS was reheated at 1177° C. and rolled to 33.4 mm round bars and air cooled to ambient temperature. The rolled bars were then reheated to 1038° C. and held for 30 minutes for hot rotary straightening. After straightening, the bars were air cooled to room temperature. The bars were rough centerless ground, ultrasonic tested for voids and then centerless ground to final size.
For manufacturing of clad-wires, the grinded bars were gun-drilled to produce hollows for subsequent tube drawing. Tubes were filled with Ag-rods and cold-drawn using diamond dies and mineral oil. For a final wire diameter of 127 μm, the last intermediate annealing was carried out at a wire diameter of 157.5 μm at 900-950° C. in Argon atmosphere. From the last intermediate annealing until the final diameter of the wire, 35% cold-work were applied. Three wire lots were manufactured having UTS values of 1456, 1469 and 1474 MPa. For bare wire, the bars were further hot-rolled to 0.2 inch outer diameter followed by cold-drawing. For 102 μm final size wire, the last intermediate annealing was carried out at a wire diameter of 122 μm at 1100° C. in Argon atmosphere to apply 30% cold-work to the final size. Two wire lots were manufactured having UTS values of 1870 and 1875 MPa. The wires of inventive example 1 (Lots A & B) and the cladded wires of inventive example 1a (Lots E, F & G) were made using the alloy of Heat 1 in table 3. The wires of comparative example 2 (lots C & D) and the cladded wires of comparative example 2a (lots H, J & K) were made from the alloy of the commercial heat in table 3 obtained from Fort Wayne Metals, Inc., USA under the trade name 35 NLT®.
The processed alloy was also obtainable from SAES Smart Materials, Inc. Alloys for the further examples were acquired from SAES Smart Materials, Inc.
The microscopic inspection for microcleanliness of the inventive alloy (example 1 and example 1a with an Ag core) and of the comparative alloy (example 2 and example 2a with an Ag core) was carried out according to the procedure and test method described above. Of 4 rods with an outer diameter of 31.75 mm, 5 transverse and 5 longitudinal sections were taken according to table 1 and metallographically prepared. The sections included a continuous plane from two surface locations and through the approximated center of the bar. The metallographically prepared sections were examined in the as-polished condition by scanning electron microscopy (SEM) using backscattered electron imaging (BEI). In BEI, the brightness of sample features is proportional to the atomic weight of the elements constituting those features. Thus, in BEI, present inclusions consisting of heavier elements than the surrounding matrix material appear brighter than the matrix material. Inclusions consisting of lighter elements than the surrounding matrix material appear darker than the matrix material. Since nonmetallic inclusions (for example, oxide or nitride inclusions) consist of lighter elements than the alloys of example 1 and example 2, in BEI these ceramic inclusions appear darker than the surrounding matrix material. Images were acquired at a magnification of 500× along a diametral line extending across the entire bar. Analysis of features darker and brighter than the background was conducted on the images using image analysis software to determine the maximum dimension for each detected feature. The largest dimension and area were recorded for each individual feature. The inclusions were categorized by largest dimension into 1 □m groups up to 14 □m. The total area of the dark and bright features was also calculated. Inclusions greater than 14 □m were also counted. Features smaller than 3.0 □m were not included in the measurements.
For each section, forty-eight fields of view were evaluated. For each direction, longitudinal and transverse, 480 images with a total area of 22.6 mm2 were evaluated. The samples contained features that appeared darker and brighter than the bulk material using backscattered electron imaging. The darker features have a lower mean atomic number than the background and the brighter features have a higher mean atomic number than the background.
Results of the inclusion analysis of example 1 are illustrated in tables 4-6. Results of the inclusion analysis of example 2 are illustrated in tables 7-10. Image fields showing typical dark (ceramic) inclusions are illustrated in
According to Table 8 of example 2 (comparative), the total area of dark inclusions found is 478 μm2 (409 μm2 in longitudinal direction and 69 μm2 in transverse direction). According to Table 5 of example 1 (inventive), the total area of dark inclusions found is only 218 μm2 (121 μm2 in longitudinal direction and 97 μm2 in transverse direction). So the amount of dark inclusions (Percent of total area) in example 1 (inventive) is only 4.8 ppm (0.00048%) while in example 2 (comparative) the amount of dark inclusions is 11 ppm (0.0011%). In terms of inclusions (micro-cleanliness) this means that example 1 (inventive) is more than 2 times cleaner than example 2 (comparative).
Two lots of wire of example 1 (dia. 102 μm) were tested against two lots of wire or example 2 (same diameter—102 μm) having comparable mechanical properties (UTS of 1862-1875 MPa).
At an applied stress of 700 MPa, the wire of all four lots reached the fatigue endurance limit, means the wire does not fail and tests are stopped after 100 Million cycles. While the wire of example 1 showed no outliers at 700 MPa and below, 4 samples of example 2 failed at less than 2.7 Million cycles and two other samples ran 40-50 Million cycles. All other samples tested at an applied stress of 700 MPa and below survived 100 Million cycles without rupture. For Example 2 wire lot C, sample C25 tested at an applied stress of 700 MPa broke after only 71,790 cycles and sample C31 tested at an applied stress of 520 MPa broke after only 145,260 cycles. Sample C26 tested at an applied stress of 700 MPa broke after 47,547,540 cycles and sample C29 tested at an applied stress of 700 MPa broke after 41,282,990 cycles. For example 2 wire lot D, sample D27 tested at an applied stress of 700 MPa broke after only 549,227 cycles and sample D35 tested at an applied stress of 520 MPa broke after only 2,689,952 cycles.
SEM-images of sample C25 illustrate an inclusion at the fracture surface. In EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. This mixed-oxide inclusion was identified as the crack initiation point for the early failure of this sample. An SEM-image of sample D35 also illustrates an inclusion at the fracture surface. Again, in EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. Also this mixed-oxide inclusion can be identified as the crack initiation point for the early failure of this sample. SEM investigations of samples C31 and D27 also showed oxide-inclusions at the fracture surface which were identified causing the early failure. For both samples, the same elements (Aluminium, Magnesium, Chromium, Oxygen) illustrate high peaks in EDX analysis for these two samples.
These fatigue test results are plotted in
Three lots of example 1a/Ag28% wire (diameter 127 μm) were also tested against three lots of example 2a wire (same diameter—127 μm). All six wire lots have comparable mechanical properties (UTS of 1456-1475 MPa).
At an applied stress of 414 MPa, the wire of all four lots reached the fatigue endurance limit, means the wire does not fail and tests are stopped after 100 Million cycles. While example 1a/Ag28% wire showed no outliers at 414 MPa and below, 4 samples of example 2a/Ag28% wire failed at less than 1.4 Million cycles. All other samples tested at an applied stress of 414 MPa and below survived 100 Million cycles without rupture. For example 2a/Ag28% wire lot H, sample H24 tested at an applied stress of 414 MPa broke after only 1,041,679 cycles. Sample J18 tested at an applied stress of 518 MPa broke after 588,028 cycles and sample J23 tested at an applied stress of 414 MPa broke after 263,488 cycles. Sample K24 tested at an applied stress of 414 MPa broke after 1,355,189 cycles. As an example, SEM-images of sample J23 illustrate an inclusion at the fracture surface. In EDX analysis, high peaks for Aluminium, Magnesium, Chromium and Oxygen were found. This mixed-oxide inclusion was identified as the crack initiation point for the early failure of this sample. SEM investigations of samples H24, J18 and K24 also showed oxide-inclusions at the fracture surface which were identified causing the early failure. For all three samples, the same elements (Aluminium, Magnesium, Chromium, Oxygen) illustrate high peaks in EDX analysis for these three samples.
These fatigue test results are plotted in
A wire with thickness 25 μm was prepared according to the method described above and with compositions of the alloy as given in table 3. The wires were arranged into a lead as described in
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17175922.8 | Jun 2017 | EP | regional |
This Utility patent application claims priority to Application No. 62/519,719 filed on Jun. 14, 2017 and Application No. EP 17175922.8, filed on Jun. 14, 2017, each of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62519719 | Jun 2017 | US |
