The present invention pertains to a coated wear-resistant member, as well as a method for making a coated wear-resistant member, wherein the coating scheme is applied by physical vapor deposition (PVD). More specifically, the invention pertains to a coated wear-resistant member, as well as a method for making a coated wear-resistant member, wherein the coating scheme is applied by physical vapor deposition (PVD). The coating scheme includes a region with alternating sublayers of titanium aluminum silicon nitride and titanium aluminum nitride.
Physical Vapor Deposition (PVD) processes (often just called thin film processes) are atomistic deposition processes in which material is vaporized from a solid source and transported in the form of a vapor through a vacuum or low pressure gaseous (or plasma) environment to the substrate where it condenses. Typically, PVD processes are used to deposit films with thicknesses in the range of a few nanometers to thousands of nanometer; however they can also be used to form multilayer coatings, graded composition deposits, very thick deposits and freestanding structures. PVD processes can be used to deposit films of elements and alloys as well as compounds using reactive deposition processes. In reactive deposition processes, compounds are formed by the reaction of depositing material with the ambient gas environment such as nitrogen (e.g. titanium nitride, TiN). See Donald M. Mattox, Handbook of Physical Vapor Deposition (PVD) Processing, Society of Vacuum Coaters, Albuquerque, N. Mex. (1998), pp. 3-4.
Heretofore, coated wear-resistant members have been used in many applications wherein resistance to wear is a desirable property. Typically, a coated wear-resistant member comprises a substrate and a coating scheme on the substrate. The coating scheme may comprise a single coating layer or, in the alternative, it may comprise a plurality of coating layers. In many instances, the coating scheme provides the wear resistant property. One exemplary wear-resistant member is a coated cutting tool useful for the removal of material (e.g., metal) from a workpiece. Coated cutting tools include without limitation coated cutting inserts, coated end mills, coated drills, coated taps, and coated reamers. Metal forming is another area of use for a coated wear-resistant member. Such a coated wear component may be a coated drawing die or the like. The coated wear-resistant member has other tribological applications such as, for example, valve bodies, dies and punches.
In an application in which a coated wear-resistant member is desirable to use, it is advantageous for the coating scheme to exhibit an optimal level of hardness. In this regard, the hardness reflects the ability of the coating scheme to provide wear resistance to the coated wear-resistant member. Thus, there is a general desire to use a coating scheme that exhibits an optimal hardness wherein the coating scheme is not too brittle, but has sufficient hardness to provide wear-resistant properties. In an application in which a coated wear-resistant member is desirable to use, it is advantageous for the coating scheme to exhibit an acceptable level of adhesion to the substrate. In this regard, the ability of the coating scheme to adhere to the substrate typically results in an increase in the overall useful life of the coated wear-resistant member.
It can thus be seen that it would be desirable to provide a wear-resistant member that has a coating scheme, which exhibits a certain optimal hardness. Further, it can thus be seen that it would be desirable to provide a wear-resistant member that has a coating scheme, which exhibits an acceptable level of adhesion. It can also been that it would be desirable to provide a wear-resistant member that exhibits a certain optimal hardness in combination with an acceptable level of adhesion of the coating to the substrate. The overall goal is to provide such a coated wear-resistant member that exhibits improved performance properties in applications such as metalcutting, metal forming, and other tribological applications.
In one form thereof, the invention is a coated wear-resistant member that comprises a substrate, which has a substrate surface, and a coating scheme. The coating scheme comprises a region with alternating coating sublayers with one coating sublayer being TixAlySi100-x-yN wherein 40 atomic percent≦x≦80 atomic percent; 15 atomic percent≦y≦55 atomic percent; 4 atomic percent≦100-x-y≦15 atomic percent, and other coating sublayer being TipAl100-pN wherein 45 atomic percent≦p≦100 atomic percent. As an option, the coating scheme may further include at least one bonding region.
In another form thereof, the invention is a method for making a coated wear-resistant member comprising the steps of: providing a substrate having a substrate surface; and depositing a region of alternating coating sublayers with one coating sublayer being TixAlySi100-x-yN wherein 40 atomic percent≦x≦80 atomic percent; 15 atomic percent≦y≦55 atomic percent; 4 atomic percent≦100-x-y≦15 atomic percent, and other coating sublayer being TipAl100-pN wherein 45 atomic percent≦p≦100 atomic percent. As an option, the method may further include the step of depositing at least one bonding region.
The following is a brief description of the drawings that form a part of this patent application:
Referring to the drawings,
The coated cutting insert 50 comprises a coating scheme 60 and a substrate 62.
In the first alternative, bonding coating region is a single layer of TipAl100-pN wherein 45≦p≦100. As another option of the composition, the composition can be TipAl100-pN wherein 45≦p≦65. In reference to the thickness of the single layer of TipAl100-pN, the thickness of the single coating layer of titanium aluminum nitride can range between about 0.05 micrometers and about 4 micrometers. As an alternative, the thickness of the single layer of TipAl100-pN can range between about 0.2 micrometers and about 4 micrometers.
In the second alternative, the bonding coating region comprises a plurality of bonding coating sets wherein each bonding coating set comprises alternating bonding coating sublayers of TiN and TipAl100-pN (i.e., TiN/TipAl100-pN) wherein 45≦p≦100. As another option of the composition of the titanium aluminum nitride, the composition can be TipAl100-pN wherein 45≦p≦65.
In reference to the thickness parameters pertaining to the second alternative of the bonding coating region, the thickness of the coating layer of titanium nitride can range between about 0.002 micrometers and about 0.05 micrometers. As an alternative, the thickness of the coating layer of titanium nitride can range between about 0.002 micrometers and about 0.025 micrometers. The thickness of the coating layer of titanium aluminum nitride can range between about 0.002 micrometers and about 0.05 micrometers. As an alternative, the thickness of the coating layer of titanium aluminum nitride can range between about 0.002 micrometers and about 0.025 micrometers. The thickness of each coating set (TiN/TipAl100-pN) can range between about 0.004 micrometers and about 0.1 micrometers. As an alternative, the thickness of the coating set (TiN/TipAl100-pN) can range between about 0.004 micrometers and about 0.05 micrometers. The total thickness of TiN/TipAl100-pN bonding region can range between greater than about zero micrometers and about 4 micrometers.
The region of alternating coating sublayers (TiAlSiN/TiAlN) 110 comprises a plurality of coating sets (114A, 114B, 114C) wherein each coating set comprises a sublayer (118A, 118B, 118C) of titanium aluminum silicon nitride (TixAlySi100-x-yN, 40≦x≦80; 15≦y≦55; 4≦100-x-y≦15) and a sublayer (120A, 120B, 120C) of titanium aluminum nitride (TipAl100-pN, 45≦p≦100), wherein the coating composition is specified in atomic percent. There are number of options when it comes to the composition of the titanium aluminum silicon nitride coating layer, and there are a number of options for the composition of the titanium aluminum nitride coating layer. The total coating thickness of this alternating TiAlSiN/TiAlN coating region 110 ranges from 1 micrometer to 6 micrometer.
In reference to the composition of the titanium aluminum silicon nitride (TixAlySi100-x-yN) coating layer, one option is (TixAlySi100-x-yN) 50 atomic percent≦x≦70 atomic percent; 20 atomic percent≦y≦40 atomic percent; 7 atomic percent≦100-x-y≦10 atomic percent). A second option is (TixAlySi100-x-yN) 55 atomic percent≦x≦65 atomic percent; 25 atomic percent≦y≦35 atomic percent; 8 atomic percent≦100-x-y≦9 atomic percent). In reference to the composition of the titanium aluminum nitride (TipAl100-pN, 45≦p≦100) coating layer, one option is TipAl100-pN, wherein 45 atomic percent≦p≦65 atomic percent. Another option is TipAl100-pN, wherein p=100 atomic percent.
In reference to the thickness parameters for the coating layers 118A-C and 120A-C, The thickness of the coating layer of titanium aluminum silicon nitride can range between about 0.002 micrometers and about 0.05 micrometers. As an alternative, the thickness of the titanium aluminum silicon nitride coating layer can range between about 0.002 micrometers and about 0.025 micrometers. The thickness of the coating layer of titanium aluminum nitride can range between about 0.002 micrometers and about 0.05 micrometers. As an alternative, the thickness of the titanium aluminum nitride coating layer can range between about 0.002 micrometers and about 0.025 micrometers. In reference to the thickness of the coating sets (114A-114C), the thickness of the coating set can range between about 0.004 micrometers and about 0.05 micrometers. As an alternative, the thickness of the coating set can range between about 0.004 micrometers and about 0.025 micrometers.
For the titanium-aluminum-silicon-nitrogen coating, the coating crystal structure is face centered cubic (f.c.c.), or a mixture of f.c.c. and hexagonal close pack phase (h.c.p phase). The phase constitution is determined by selected area diffraction (SADP) using transmission electron microscope (TEM).
In reference to top coating region 142, the coating layer comprises titanium aluminum silicon nitride (TixAlySi100-x-yN, 40≦x≦80; 15≦y≦55; 4≦100-x-y≦15). In reference to the composition of the titanium aluminum silicon nitride (TixAlySi100-x-yN) coating layer, one option is (TixAlySi100-x-yN) 50≦x≦70; 20≦y≦40; 7≦100-x-y≦10). A second option is (TixAlySi100-x-yN) 55≦x≦65; 25≦y≦35; 8≦100-x-y≦9). For the titanium-aluminum-silicon-nitrogen coating, the coating crystal structure is face centered cubic (f.c.c.), or a mixture of f.c.c. and hexagonal close pack phase (h.c.p phase). The phase constitution is determined by selected area diffraction (SADP) using transmission electron microscope (TEM). The thickness of the coating layer of titanium aluminum silicon nitride can range between greater than about zero micrometers and about 3 micrometers. As an alternative, the thickness of the titanium aluminum silicon nitride coating layer can range between about 0.2 micrometers and about 2 micrometers.
In this work, the cathodic arc deposition method is used to deposit the coatings. The coating chamber was pumped down to a pressure equal to about 1×10−3 Pa. The parts, i.e., substrates to be coated, were then heated up to a temperature equal to about 550° C. using a radiation heater. In these examples, the substrate comprised of tungsten carbide containing about 6% cobalt and about 0.4% chromium. The surfaces of each substrate was cleaned by argon etching using a DC voltage of about −50 volts to about −200 volts in an argon pressure equal to about 0.2 Pa.
Powder metallurgical targets of titanium-aluminum-silicon and titanium-aluminum were used in a reactive atmosphere of nitrogen (or nitrogen in an inert gas) to deposit the titanium-aluminum-silicon-nitrogen coating and titanium-aluminum-nitrogen coatings layers. The chemistry, i.e., composition, of the coating layers was controlled by using titanium-aluminum-silicon and titanium-aluminum targets of different compositions. The working pressure to deposit each coating layer was within the range of between about 0.5 Pa to about 6 Pa.
There were six different coating compositions of the titanium-aluminum-silicon-nitrogen coating. The substrate for each one of the coating was: cemented tungsten carbide containing about 6% cobalt and about 0.4% chromium. Table I below sets forth the content of the titanium, aluminum and silicon components in each one of the six coatings. The overall coating has a composition according to the following formula (In atomic percent): TixAlySi(100-x-y)N wherein x and y are in atomic percent of the sum of the titanium, aluminum, and silicon contents. The composition of the coating layers was measured by EDS technique using SEM.
Table II below sets forth properties for each one of the Coating Nos. 1 through 6. The term “f.c.c.” means face-centered cubic, and the term “h.c.p.” means hexagonal close-packed.
The hardness and Young's modulus are reported in gigapascals (GPa), and were measured using a nanoindenter using ISO 14577-1 standard procedure. The crystal structure is reported and was determined by transmission electron microscope (TEM).
The composition and properties of Coating No. 2 are set forth in Table I and Table II above.
The composition and properties of Coating No. 4 are set forth in Table I and Table II above.
The composition and properties of Coating No. 6 are set forth in Table I and Table II above.
Coatings No. 1-6 have excellent hardness, however, these coatings can possibly flake off on sharp cutting edges when deposited as a single layer. Coating adhesion can be improved by (1) adding Si free bonding layers such as TiN, TiAlN and/or mixture layer of TiN/TiALN; and (2) alternating TiAlSiN coating and TiAlN coating. Referring to Table III, Coatings Nos. 8-13 show coatings that have at least one bonding region and alternating TiAlSlN/TiAlN coating region. Coating No. 7 is a commercial prior art AlTiN coating shat is being used for turning and milling applications. Coatings Nos. 8 through 13 shows higher hardness than the commercial (prior art) coating No. 7. In Table III, the hardness and Young's modulus are reported in gigapascals (GPa), and were measured using a nanoindenter using ISO 14577-1 standard procedure.
First comparative tests in the continuous turning of 304 stainless steel were conducted comparing the commercial Al61Ti39N coating layer against Coating Layer No. 8. The cutting conditions are set forth below: speed=250 meters/minute; feed=0.25 millimeters/revolution; depth of cut=2.03 mm doc; insert style CNMG432-MP; lead angle=−5 degrees; coolant=flood. The end of life criteria were 0.3 mm wear on the cutting insert flank surface.
Second comparative tests in the continuous turning of 304 stainless steel were conducted comparing the commercial Al61Ti39N coating layer against Coating Layer No. 8. The cutting conditions are set forth below: speed=198 meters/minute; feed=0.2 millimeters/revolution; depth of cut=2.03 mm doc; insert style CNMG432-MP; lead angle=−5 degrees; coolant=flood. The end of life criteria were 0.3 mm wear on the cutting insert flank surface. The commercial coating No. 7 failed after 18.4 minutes. Coating No 11 failed after 26.2 minutes of cutting, while the Coatings Nos. 9, 10 and 12 do not reach the failure criteria after 30 minutes of cutting.
Third comparative tests in the continuous turning of 304 stainless steel were conducted comparing the commercial Al61Ti39N coating layer against Coating Layer No. 13. The cutting conditions are set forth below: speed=250 meters/minute; feed=0.25 millimeters/revolution; depth of cut=2.03 mm doc; insert style CNMG432-MP; lead angle=−5 degrees; coolant=flood. The end of life criteria were 0.3 mm wear on the cutting insert flank surface. The commercial coating Al61Ti39N failed after 8 minutes of cutting, while the Coating No. 13 lasts 13.1 minutes.
It is apparent from the above description that the inventive coating layers provide a wear-resistant member that exhibits a certain optimal hardness. Further, it can thus be seen that the inventive coating layers provide a wear-resistant member has a coating which exhibits an acceptable level of adhesion. It can also been that the inventive coating layers provide a wear-resistant member that exhibits a certain optimal hardness in combination with an acceptable level of adhesion of the coating to the substrate. It is apparent that the inventive coating layers provide a wear-resistant member which achieves the overall goal to provide a coated wear-resistant member that exhibits improved performance properties.
Here, the specific wear-resistant member is a coated cutting insert. However, there should be an appreciation that there is the expectation that the improved properties would exists in other kinds of wear-resistant members (e.g., punches, die and mold)
The patents and other documents identified herein are hereby incorporated in their entirety by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. There is the intention that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The following claims indicate the true scope and spirit of the invention.