Kudinova K. Synthesis of ultra-dispersed modified layers on hard layers by plasma treatment

The thesis is devoted to formation of modified layers with ultra-dispersed structure and improved level of exploitation qualities at surface treatment of hard alloy plates by highly concentrated plasma jet plasma jet. A mathematical simulatuioion of the process of plasma surface modification of hard alloy tools was carried out, as well as engineering methods of evaluation of optimal treatment modes, based on solution of heat conductivity equation, which is to make it possible to solve both a direct assignment -determination of Тmax and W at specified treatment conditions and a reverse problem of evaluating the required (optimal) modes of plasma treatment (I, q, V). Application of the developed simulation model allowed carrying out of the parameters of thermal cycles of plasma heating of hard alloy plates. Also investigated were the mechanisms of structural transformations in tool hard alloys at surface plasma modification. Regularities of structural transformations in hard alloys at heating with highly concentrated plasma jet were revealed. It was found out that the highest strengthening effect for alloys of TK and BK types (HV?1700) could be reached at plasma treatment without melting of the composition with transformations of carbides and in the matrix. Specified was the method of testing and resistance to cracking, destruction and wear mechanisms of tool hard alloys with modified layer were investigated. It was established that plasma modification led to improved (20 % higher) resistance to crack formation КIc of hard alloys, as compared to the original state, dispersed energy of destruction, due to formation of meso-structural groups being an additional factor of improving resistance to crack formation in modified hard alloys. Technological equipment, required for carrying out plasma treatment was designed, allowing fixation of hard alloy plates of different shapes at different angles of inclination and at different distances from the source of heating. Also designed were the processes of plasma modification of cutting tools, made of hard alloys. A structural diagram of the synthesis of modified layers on hard alloy tools after plasma modification was developed. Prescribed were recommendations, regarding selection of optimal arrangement of the modified area on hard alloy plates. Investigations of durability of hard alloy plates after plasma modifying investigation were performed. It was found out that following plasma modification of hard alloy tools, their strength and durability could become 2,5 to 3 times higher.