Influence of plasma nitriding on dry wear, corrosion and tribocorrosion performance of 17-4 precipitation hardening stainless steelauswirkungen des plasmanitrierens von 17-4 ausscheidungsgeharteten edelstahls auf verschleiss, korrosion und tribokorrosionsverhalten

Abstract

Plasma nitriding treatment of 17-4 precipitation hardening stainless steels was carried out at 400 degrees C and 450 degrees C using a direct current unit. The nitriding layer thicknesses of the plasma nitrided at 400 degrees C and 450 degrees C were measured as 37.29 mu m and 49.97 mu m, respectively. The plasma nitrided sample at 400 degrees C presented dominant martensite and retained austenite phases; however, the height of main martensite diffraction peaks increased at 450 degrees C. The hardness results demonstrated that the samples at 400 degrees C and 450 degrees C were 2.9 and 3.1 times as hard as the untreated sample, respectively. The wear rate values of the sample at 450 degrees C showed a decrease by 19 % in the corrosive salt solution and 57 % in the dry-sliding condition compared with that of untreated sample. The corrosion potential of the sample at 400 degrees C had more positive potential value and lower current density value than those of at 450 degrees C. The corrosion resistance of the sample at 400 degrees C improved due to the positive effect of the retained austenite phase. In this study, the wear was more dominant rather than corrosion, therefore plasma nitrided sample at 450 degrees C showed the best dry wear and tribocorrosion resistance.