Papers by Keyword: Diamond Composite

Abstract: Thermally Stable Diamond Composite (TSDC) has high thermal stability and high wear resistance, and hence is potential to be used as cutting tips for hard rock cutting. Understanding the failure behavior of the TSDC tips during practical rock cutting is a key to enable the TSDC cutting tips to be applied successfully in mining and construction industries. Previous research has shown that the character of random failures due to excessive bending force on TSDC tips is of a major concern, and an approach to estimation of the failure probability of TSDC tips for cutting a rock segment has been developed. However, this approach requires the acquisition of the total cutting length of rock by a tip since it is brand new to it is failed, which can limit the application of the approach. In this paper, a simplified approach is proposed and compared with the existing approach through a numerical case study.

Abstract: For the enhancement of chemical and mechanical adhesion of natural diamond particles with a hard-alloy matrix during the synthesis of diamond-abrasive composites the hybrid technology which combined in one technological process the thermal diffusion metallization of diamond particles and sintering by the developed scheme of the self-dosed impregnation is proposed. This technology does not include a reheating of the metallized coating that causes its destruction and enhances graphitization of diamond thus limiting the application of metallization method for improvement of diamond retention and creation of high-functional composites for diamond tools. Formation and preservation of adhesion-durable metallized coating is confirmed by experiments simulating the conditions of high temperature interaction of diamond with a carbide-forming metal and a hard-alloy matrix during the sintering of special samples using the regimes of developed technological process. The structural and phase state of the transition zone is studied by scanning electron microscopy, X-ray structure analysis and X-ray phase analysis of the partition surfaces of the contact zone between the diamond and the matrix obtained by tensile testing of special samples. Comparative service properties tests of prototype and control samples of diamond dressers confirmed efficiency of the developed hybrid technology for the creation of diamond tools.

Abstract: Preliminary metallization of the diamond component, which promotes the formation of chemical bonds on the diamond-matrix contact during subsequent sintering, is used to increase the strength of diamond retention and the durability of diamond-containing metal matrix composites. There are restrictions on carrying out metallization to create diamond composites with a cemented carbide matrix, since reheating the metallized coating at high sintering temperatures of carbide powders leads to its destruction, diamond graphitization and deterioration of the material properties. The structural-phase state in the diamond-matrix contact zone has been studied and the main factors providing the strength of diamond retention in diamond-cemented carbide composites obtained by hybrid technology that excludes the reheating of the metallized coating have been revealed. It was revealed, that the developed hybrid technology combining the thermal diffusion metallization of diamond and sintering according to the self-dosed impregnation scheme in one cycle ensures the production and preservation of the metallized coating by the methods of scanning electron microscopy, X-ray diffraction and X-ray phase analysis, Raman spectroscopy. Comparative tests have been carried out and it is shown that the specific productivity of experimental samples of a diamond tool (ruling pencils) with a metallized diamond component is on 39% higher than same parameter of pencils without metallization.

Abstract: The conducted study belongs to a field of fundamental and application-oriented issues of interphase interaction and formation of interfacial layers between a filler and matrix during the synthesis of composite systems. The factors determining the strength of the diamonds retention in a hard-alloy matrix of abrasive composites obtained by the hybrid synthesis technology with thermal diffusion metallization of diamond particles and sintering by a scheme of the self-metering impregnation were studied. Chemical composition, morphology and distribution of the reaction products, the nature of the resulting carbon phases in the contact zone between the diamond and matrix were investigated using scanning electron microscopy, X-ray phase analysis, Raman spectroscopy and atomic force microscopy. It was found that the increase of physical and chemical adhesion of diamond with the matrix during the synthesis of composites by the developed technology occurs due to the formation of high nano- and submicronic roughness of the diamond surface, formation of island-type metallized coating, dense filling of gaps by nanoscale layers of metal-infiltrate. Free carbon (graphite) was found in small quantities in the form of micron dimension separate inclusions. The revealed multilevel hierarchy of the high-structured morphological forms of the elements of the transitional layers has provided the solidity and strength of the joint between diamond and matrix.

Abstract: Thermally Stable Diamond Composite (TSDC) tips have attracted a great attention of rock cutting industry due to the higher thermal stability and high wear resistance of TSDC. To make the TSDC tipped picks practical for real application, it is important to understand the failure behavior of the TSDC tips for rock cutting. One of the failure characters of TSDC tips is random failures. In this paper, a method is proposed to calculate the failure probability of TSDC tips for cutting individual rock segments. This method enables to link the segment length to the failure probability of the tip for cutting the segment. A numerical case study is presented to validate the method. The method can effectively reduce the impact of the number of segments on failure probability estimation accuracy.

Abstract: The carbide forming is proposed to improve interfacial bonding between diamond particles and copper-matrix for diamond/copper composites. The volume fraction of diamond and minor titanium are optimized. The microstructures, thermal properties, interface reaction production and its effect of minor titanium on the properties of the composites are investigated. The results show that the bonding force and thermal conductivity of the diamond/Cu-Ti alloys composites is much weaker and lower than that of the coated-diamond/Cu. the thermal conductivity of coated-60 vol. % diamond/Cu composites is 618 W/m K which is 80 % of the theoretical prediction value. The high thermal conductivity has been achieved by forming the titanium carbide at diamond/copper interface to gain a good interface.

Abstract: Picks are commonly used cutting tools for mechanical excavation. Diamond composite is replacing tungsten carbide as cutting tips of the picks in hard rock cutting. Tips made of Thermal Stable Diamond Composite (TSDC) have high potential for improving tool life because of its high wear resistance, high hardness, high compressive strength and high thermal stability. However, as TSDC is a type of new material, the technology for its production is still unstable, which often results in considerable variations in the material properties of cutting tips. These variations can significantly affect the optimization of tip design. The conventional design approach based on mean values or extreme values cannot effectively optimize the design of cutting tip due to over or under-estimation of tip failure risks. To address this issue, in this study, a probabilistic approach is proposed to model the property variations of TSDC tips and estimate tip failure risks under a given operational circumstance using reliability theory. The new approach enables designers and operators to estimate the failure risks of cutting tips with a specified confidence level.

Abstract: This paper presents the results on the strength evaluation of sintered diamond-based composites with Co binder. The method of intensive electrosintering with a short heating pulse was applied by a high pressure of 0.5 GPa and a time of 2-40 s. Composites with different compositions and for different purposes, such as rock drilling and dressing tools, were investigated. The reactive cell was design with the purpose of preserving the diamond properties from the detrimental sintering temperature exposure. The results of this electrosintering technology permitted to obtain improved composites to be used in tools with higher indexes of performance and productivity.

Abstract: The present work comprises a study about the possibility of obtaining polycrystalline diamond cutters through a novel method of sintering both layers at the same time. This possibility was tested through the sintering of a diamond layer over a hard metal (WC+15wt%Co) support under conditions of 5.0 and 6.5 GPa of pressure and 1400 to 1600º C of temperature. The sintering conditions were imposed in two ways: directly, or with pre-sintering. The samples were tested by measuring microhardness, wear resistance, densification, and SEM. The results of the tests have shown the possibility of obtaining good quality inserts by sintering both layers of compacted powder.

Abstract: The ideal thermal management material working as heat sink and heat spreader should have a high thermal conductivity combined with a reduced and tailorable thermal expansion. To meet these market demands copper composites reinforced with diamond particles were fabricated by a powder metallurgical method (powder mixing with subsequent pressure assisted consolidation). In order to design the interfacial behaviour between copper and the reinforcement different alloying elements, chromium or boron, were added to the copper matrix. The produced composites exhibit a thermal conductivity up to 700 W/mK combined with a coefficient of thermal expansion (CTE) of 7-8 x 10-6/K. The copper composites with good interfacial bonding show only small decrease in thermal conductivity and a relatively stable CTE after the thermal cycling test.