EFFECT OF γ→ MARTENSITIC TRANSFORMATION ON THE TRIBOLOGICAL PROPERTIES OF CHROMIUM–MANGANESE AUSTENITIC STEELS

The paper studies the effect of ε (hcp) martensite on the structure and tribological properties of chromium-manganese metastable austenitic steels. The effect of TiC carbide particles on the friction coefficient and wear resistance of Cr–Mn austenitic steels is considered. Structural transformations occurring in the surface layers of the steel in the course of frictional processing are studied via methods of metallography, X-ray diffraction and electron microscopy analysis. It has been found that the formation of nanocrystalline hcp martensite in the steels under study decreases considerably their friction coefficient and increases their resistance to adhesive wear in comparison with the cases of the 40Kh25N20 stable austenitic stainless steel and the 12Kh18N9 austenitic stainless steel, the latter being metastable to γ→α martensitic transformation. The presence of 1–4.5 wt % of TiC carbide particles in the structure of the steels increases the friction coefficient of the materials and decreased their wear resistance. The ε phase in chromium-manganese austenitic steels is more capable of strain-induced hardening under friction than the ε phase in iron-manganese alloys. Accumulation of fine TiC particles of in the surface layer of the titanium-alloyed chromiummanganese austenitic steels has been detected.