Patent Application
20190247928
The present disclosure relates to sintering of polycrystalline diamond (PCD) materials, which are able to withstand the high temperatures associated with cutting, drilling, and mining applications. The diamond particles, on the order of 1 to 50 μm diameter, are treated to impart greater reactivity for diamond formation, leading to PCD that is more thermally stable.
Conventionally, PCD is formed by sintering diamond particles under high pressure and high temperature (HPHT) in the presence of a transition metal catalyst, typically cobalt. HPHT conditions for PCD sintering include pressures at or above 55 kBar and temperatures at or above 1400° C. At those conditions, the transition metal dissolves carbon from the diamond and re-precipitates it as diamond, forming inter-particle diamond bonds to make a sintered diamond compact. After sintering, the transition metal catalyst remains in the diamond compact, and can reduce its thermal stability during use. This is because differences in the coefficient of thermal expansion (CTE) between the diamond and the metal catalysts become apparent due to the frictional heat generated during use. The CTE mis-match induces micro-cracks in the diamond compact, leading to faster erosion. Also, at the elevated temperatures encountered during use, the metal catalyst may promote the back-conversion of diamond to graphite or amorphous carbon, leading to more modes of failure.
In order to overcome these problems, it would be desirable to sinter PCD with very little or no transition metal catalysts. By using diamond particles that are more reactive and catalyst systems that are more effective, a more thermally stable and higher performing PCD can be made.
In one embodiment, a cutting element for a tool may comprise a substrate; a polycrystalline diamond table bonded to the substrate which is produced by sintering diamond particles with enhanced reactivity.
In another exemplary embodiment, a cutting element for a tool may comprise a substrate; a polycrystalline diamond table bonded to the substrate which is produced by sintering diamond particles with enhanced reactivity mixed with standard diamond particles.
In a third exemplary embodiment, a cutting element for a tool may comprise a substrate; a polycrystalline diamond table bonded to the substrate which is produced by sintering diamond particles with enhanced reactivity mixed with standard diamond particles and other chemical additives.
The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements:
Before the present methods, systems and materials are described, it is to be understood that this disclosure is not limited to the particular methodologies, systems and materials described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope. For example, as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. In addition, the word “comprising” as used herein is intended to mean “including but not limited to.” Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45% to 55%. When the term, “substantially free”, is used referring to catalyst in interstices, interstitial matrix, or in a volume of polycrystalline element body, such as polycrystalline diamond, it should be understood that many, if not all, of the surfaces of the adjacent diamond crystals may still have a coating of the catalyst. Likewise, when the term “substantially free” is used referring to catalyst on the surfaces of the diamond crystals, there may still be catalyst present in the adjacent interstices.
As used herein, the term “graphene” refers to a form of carbon, in which the carbon atoms are arranged in a 2-dimensional hexagonal lattice, that can be as thin as one atomic layer (<1 nm). In a more specific embodiment, the single-layer graphene may each have a thickness of 0.35 to 1.7 nm. These layers can also exist as double or multiple stacked sheets.
As used herein, the term ‘graphene treated diamond’ refers to diamond particles in atomic-level contact with single layer, bi-layer, or multi-layer graphene.
As used herein, the term “graphane” refers to a form of hydrocarbon, in which the carbon atoms are arranged in a 2-dimensional hexagonal lattice, as thin as one atomic layer, in which at least some of the carbon atoms have hydrogen atoms bonded to them and which gives rise to a characteristic Raman spectrum exhibiting peaks at 1330 cm−1 (labeled ‘D’), 1580 cm−1 (labeled ‘G’), 2700 cm−1 (labeled ‘2D’) and 2950 cm−1 (corresponding to the C—H bond) and in which the D/G peak intensity ratio is >0.5. Graphane can also be described as graphene that has been fully or partially hydrogenated.
As used herein, the term ‘graphane treated diamond’ refers to diamond particles in atomic-level contact with graphane.
The sintered PCD cutters, representing a polycrystalline diamond bonded to a tungsten carbide substrate, were fabricated using the HPHT process. After fabrication all PCD cutters were shaped by grinding and polishing to a cylindrical shape.
Raman spectroscopy (Nakamoto, K., Infrared and Raman spectra of inorganic and coordination compounds. 5th ed., 1997, New York: John Wiley and Sons, Inc.) is used to characterize graphene, graphane, graphite, and diamond.
Scanning electron microscopy (SEM) and elemental analysis (EDS) were performed on a JSM-7200F SEM with 5 to 15 kV accelerating voltage. EDS was done with an Oxford XMAX with solid state detector.
Diamond can be directly converted from graphite, under high pressure and high temperature conditions. The underlying mechanism at the atomic level may be correlated to the p-electrons on carbon atoms of graphite, which may attract every other carbon atom in graphite to cause the carbon ring to pucker, thus forming a diamond material, as sp3 bonded carbon, from sp2 bonded carbon. To evaluate the effect of temperature and pressure, the thermodynamic driving force of diamond formation was calculated (Table 1) at pressure from 45 to 75 kbar with temperature ranges from 700° C. to 2000° C. A positive driving force indicates that graphite to diamond conversion is favorable from a thermodynamic point of view; and a higher number indicates the graphite to diamond conversion is more likely to occur. But the kinetics of this reaction is generally too slow for industrial processes, thus the need for metal catalysts, such as cobalt, in conventional methods.
Other metal catalysts, copper (Cu) and tin (Sn), have been investigated for diamond synthesis. At this temperature range (1400° C. to 1800° C.), previous studies suggested that extremely long sintering time is required to make these two catalysts functional (about 2 to 20 hours). For example, using Cu as a catalyst, the sintering time is at least 5 h for the experiments conducted between 1400° C. to 1700° C. [S. K. Singhal et al., Temperature dependence of growth of diamond from Cu—C system under high pressure. Journal of Crystal Growth 154 (1995) 297-302]. When temperature increased to 1800° C., sintering time can be slightly shortened but still need 4 h [I. N. Kupriyanov et al., HPHT growth and characterization of diamond from a copper-carbon system, Diamond & Related Materials 69 (2016) 198-206]. Similar for Sn, the sintering time (20 h) is even longer than Cu in the 1600° C. condition [Y. N. Palyanov et al., Diamond crystallization from a tin-carbon system at HPHT conditions, Diamond & Related Materials 58 (2015) 40-45]. And at 1700° C. and 1800° C., the sintering time can be reduced to 2 h but still considered as sluggish process. Overall in the temperature range 1400° C.-1800° C., none of these long reaction time processes can be considered as practical for industrial applications.
However, the low catalytic activity can alternatively be solved by starting with a material that is more reactive, thereby eliminating, or substantially reducing, the need for a cobalt metal catalyst. Non-diamond and non-graphite carbon that may be more reactive include, but are not limited to, graphene, graphane, carbon nanotubes, and buckyballs. Such nano-scale materials would be expected to be more reactive (i.e. thermodynamically unstable) sources of carbon that can convert to diamond under the appropriate temperature and pressure conditions. In particular, graphene or graphane, subjected to HPHT, in the presence of diamond particles, could be expected to convert to diamond and thus form a sintered solid PCD compact.
The location of the graphene or graphane in relation to the diamond particles is critical for the PCD compact to form, as shown in
Conventional mixing techniques, however, are not designed to both mix two dissimilar components (e.g. graphene and diamond) and also ensure the precise placement of one component relative to another. Therefore, non-conventional methods must be employed.
By non-conventional means, the graphene or graphane can be placed advantageously to allow for diamond to diamond sintering to take place. Rather than conventionally mixing graphene or graphane with diamond particles, the diamond particles are graphene treated or graphane treated.
There exist additional functionalities of Cu and Sn other than catalyst, when the temperature is consistently lower than 1800° C. At this temperature, Cu and Sn additives may facilitate the treatment of diamond particles with graphene or graphane. Also, the Cu and Sn can form a solution with a catalytic metal, such as Co, to reduce the CTE mismatch between the Co and diamond. This would promote the thermal stability and increase the performance of PCD. Another effect is that Cu and Sn may effectively prevent the segregation and improve the homogeneous distribution of metal in the PCD layer. All of these effects in combination may lead to an improved sintering process and product performance.
Exemplary embodiments disclose a cutting element for a tool and a method of making the cutting element. One process for making PCD cutting elements involves the mixing of various sized graphene or graphane treated diamond with (or without) standard diamond particles 1, loading into a tantalum cup 3 and placing a substrate 2 in the cup, as shown in
In an exemplary embodiment (
The PCD cutter 1 comprises a substrate 2, which is made of hard metal, alloy, or composite, such as cemented carbide or cobalt sintered tungsten carbide (WC—Co). PCD cutter blank can be later machined to a desired shape and dimensions. The recovered polycrystalline diamond table may be attached or joined coherently to the substrate along the interface 4.
Exemplary embodiments are provided for the detailed process as described above.
2.0 g of graphene treated diamond (particle size 0.6 μm to 100 μm) was loaded into a 16 mm diameter Ta cup, followed by the placement of tungsten carbide substrate. This assembly was built into a high pressure cell and pressed at 45 kbar to 80 kbar and 700° C. to 1800° C. for up to 30 minutes, then brought back to atmospheric pressure and recovered from the high pressure cell.
2.0 g graphene treated diamond (particle size 0.6 μm to 100 μm) was mixed with 0.15 g fine diamond feed (particle size 0.6 μm to 1.8 μm) and 0.02 g chemical additives (e.g. Pb). This obtained mixture was loaded into a Ta cup, and then a tungsten carbide substrate was placed. The assembly was built into a high pressure cells and pressed at 45 kbar to 80 kbar and 700° C. to 1800° C. for up to 1 hour.
The PCD samples sintered from graphene treated diamond particles were characterized by SEM and the results are presented in
The uniformity of the sample can be further appreciated by the distribution of diamond, Co, W and Ru in the elemental analysis of the cross-section.
In contrast, PCD made from standard diamond (the control sample) exhibited a non-uniform distribution. A representative result is shown in
The mechanical performance of the PCD cutter is typically characterized by abrasion resistance tests, by cutting granite on a standard vertical turret lathe.
As the plots clearly show, the wear behavior of most PCD samples were similar at early stages, except for sample Con._1. This sample failed early in the test and only one data point was collected. The matching sample, Gra._1 however, performed very well, with 5.0×107 mm3 rock volume per 13.05 mm3 of cutter wear. Similarly, comparing sample Gra._2 to Con._2, it can be seen that Gra._2 shows significantly better performance. For example, after removing the same amount of 3.75×107 mm3 rock, the cutter wear of Gra._2 is 5.7 mm3, about 70% less than the 16.2 mm3 of Con._2. The performance of Gra._3 and Con._3 are more closely matched, especially in the early stages of the test, but Gra._3 provides better performance overall. When removing 3.34×107 mm3 rock volume, the cutter wear of Gra._3 is 4.9 mm3 while it is 5.8 mm3 for Con._3. The performance of Gra+Pb is comparable to Gra._1, with 5.43×107 mm3 rock volume per 12.8 mm3 of cutter wear. These measurable performance improvements suggest an improvement in thermal stability of cutters sintered from graphene treated diamond particles.
| Number | Date | Country | |
|---|---|---|---|
| 62629819 | Feb 2018 | US |
