Structure-phase transformation of high speed steel by various high intensity ion-plasma treatments

The influence of compressive plasma flow (CPF) treatment on structure and mechanical properties of AISI M2 steel was investigated and was compared with the influences of other known high intensive techniques such as high current ion implantation (HCII) and plasma immersion ion implantation (PIII) of nitrogen. The formation of structure-phase state of steel during HCII takes place under more equilibrium condition than during PIII and CPF treatments. So the structure of steel forming during HCII is more stable and is a superposition of martensite, hardening carbides, carbonitrides and small quantity of austenite. The condition of CPF treatment process is essentially more unequilibrium. It is similar to PIII but is more intensive. So the structure of thick (approx. 30 μm) surface layer of steel undergoes great changes—decay of main hardening M 6C carbide and formation of expanded austenite doped by nitrogen and alloying elements of steel. The presence of this austenite improves wear resistance of steel while the decay of hardening carbides leads to microhardness decrease.