Formation of diamond-containing ceramic abrasive material by microarc oxidation

Abstract

The paper describes the features of the electrochemical formation of a modern abrasive a diamond-bearing composite material with a ceramic matrix based on aluminum oxide and investigation on its tribological properties. The technology for forming an abrasive superhard material involves the electrochemical conversion of an aluminum binder into a corundum matrix using microarc oxidation of the surface of parts obtained by powder metallurgy from aluminum powder and dispersed diamond of various fractions. The authors applied the technology of chemical metallization with copper in order to protect the diamond surface from oxidation and to increase its mechanical strength. The try-outs of the modes for producing diamond-bearing composite material samples, and comparative tribological tests were conducted on the specially designed equipment. There are the identified factors that determine the features of the technology of diamond-bearing composite material electrochemical formation on various bulk density workpieces, as well as workpieces with a varying percentage composition of material components. It has been established that the diamond metallization degree significantly affects the oxidation process. It is almost impossible to produce composite ceramic material by microarc oxidation with diamonds coated with nanodispersed copper with a metallization degree of over 100%. A change in the material diamond concentration does not affect the creation of stable spark discharges that form the α-modification aluminum oxide. Therefore, the choice of diamond concentration, as well as its grit size, can be based on the required tribological properties of a tool material and the physical and mechanical properties of a part to be processed, and its surface roughness. The relative density of a diamond-bearing composite material sintered blank for microarc oxidation should be 80–90%. In this case, the formed material has optimal physicomechanical and tribotechnical properties. The optimal alkali concentration in the electrolyte for the maximum diamond-bearing composite material thickness is about 2 g/l. The comparative tribotechnical tests have confirmed the advantages of diamond-bearing ceramic material compared with traditional analogues. It has been established that, when processing 16 GPa hardness ceramics, the relative diamond consumption of a ceramic matrix material is 3.3 and 6 times lower than that of materials with a metal and organic bond, respectively. Unlike traditional materials, the volumetric cutting ability of an abrasive tool made of new material initially exceeds this characteristic for metal bond circles by 1.6 times, for organic bond circles by 3.6 times and almost does not decrease during processing. The new synthesized abrasive material will be in demand for producing abrasive tools for high-performance precision microprocessing of superhard materials in various sectors of the precision industry, instrument making, jewelry and watch industry.