Scratch testing of plasma nitrided and nitrocarburized AISI 321 steel: Influence of the treatment temperature

•Thicker and harder layers were found with 500 °C treatments.•In progressive scratch, lower and attenuated friction was found in 400 °C layers.•Worse scratch failures mechanisms were observed in the 500 °C layers.•In multipass scratch, lower friction was found in the 400 °C layers.•After 100 scratch passes, nitriding at 400 °C shows the lowest volume loss. This work studies the effect of treatment temperature on plasma nitrided and nitrocarburized AISI 321 stainless steel by scratch test in two modes: progressive and multipass. The treatments were conducted at 400 and 500 °C for 6 h. Progressive scratch revealed a detrimental influence of increasing the temperature in both layers, failure mechanisms worsened with the 500 °C treatments, besides a higher residual depth and a more fluctuating coefficient of friction (COF) were observed. In multipass scratch, a higher and scattered COF was found after 100 passes in the 500 °C layers. The lowest volume loss and COF were registered for nitriding at 400 °C, although nitrocarburizing at 400 °C showed the best integrity with milder failures and low and stable friction.