Wpływ austenitu szczątkowego na utwardzenie warstwy wierzchniej konstytuowanej w procesie tarcia tocznego z poślizgiem

Abstract

On the base of microhardness and hardness measurements changes in the hardening of the superficial layer of samples subjected to rolling-sliding friction in a range of Hertz stresses of 300÷1400MPa were determined. There were tested carburized samples of steel 12HN3A with carburized layer structure martesitic with minimum retained austenite and with structure containing 40% retained austenite. For martensite samples a slight hardening up to a stress of c. 500 MPa was observed; at high stress there was a drop in microhardness and hardness of the superficial layer. In the superficial layer of samples with 40% retained austenite an increase in microhardness up to a stress of 1000 MPa amd an increase in hardness up to a stress of 1400 MPa was observed. It was found on the base X-ray and microscopic examinations that in the range of favourable action of retained austenite upon resistance to wear (i.e. above 700 MPa stress) a basic factor of hardening is martensitic transformation of retained austenite into strain induced martensite.