Optimization of compound layer thickness for wear resistance of nitrocarburized H11 steels

摘要

Nitrocarburizing improves the wear resistance of components and hence is advantageously applied tohot working dies. The improvement is related to the development of surfacial compound layer ofepsilon carbonitride. H11 steels, by virtue of high chromium content, develop only a very thincompound layer and hence the benefit accrued is limited. In this study, higher treatment temperatureswere employed in a Sursulf salt bath to increase the layer thickness and the wear resistance of treatedspecimens assessed using pin-on-disc test geometry. It was found that the wear rate was lower withincreasing layer thickness, but because of loss of core strength, the treatment temperature of 700℃could not be recommended. A maximum temperature of 650℃ appears to be the near optimum forimproved wear resistance without a serious compromise on the core strength required for forging dies.Another significant observation was that there was no spalling or debonding of the compound layerand one of the reasons was the jagged interface between the compound layer and the diffusion zone.