Change in high-temperature wear resistance of high-speed steel by plasma nitriding

Abstract

The present paper contains results of tribology testing the surface layer of high-speed steel nitrated in electrolytic plasma. Tribology tests were conducted under the temperature of 500 °С, 550 °С and 600 vС degrees using ball-on-disc method. Such parameters as wear intensity and friction coefficient were applied to analyze wear resistance. It is found, that wear resistance of nitrated layer of high-speed steel changes depending on ambient temperature and it showed higher resistance against the wearing process up to 550 °С degrees. It is established, that the rise in testing temperature up to 600 °С degrees resulted in degradation of wear resistance and increase in friction coefficient. The paper addresses the main factors improving wear resistance increase of high-speed steel surface layer after electrolyte-plasma nitriding. The optimum condition of electrolyte-plasma nitriding of high-speed steel Р6М5 in electrolyte on the basis of carbamide which allows to make saturation of surface by nitrogen from low-temperature plasma is experimentally positioned and to receive the modified bed of high hardness and a wear resistance. It is positioned that a major factor responsible for a wear resistance of the nitriding layers at high temperatures is formation of the nitride martensite which possesses the major heat capacity in comparison with iron, and finely divided nitride particles.