Damage Mechanisms of Plasma, Gas and Salt Bath Nitrocarburized Steel in Lab-Scale Sliding Test

Abstract

Nitrocarburized steel surfaces are often used in tribological forming applications due to their beneficial sliding properties. One typical application field can be found in bending machines where the nitrocarburized layer can withstand massive volume loss and prevent from adhesion of the work sheet material. However, under non-lubricated sliding conditions abrupt failure of the nitrocarburized layer can occur, which results in pronounced increase of friction and wear. In order to characterise the wear mechanisms of nitrocarburized surfaces under non-lubricated sliding conditions, a lab-scale study was carried out. Different nitrocarburizing processes including plasma, gas and salt bath nitrocarburizing were investigated. Oscillating sliding tests with DIN 100Cr6 bearing steel cylinder sliding against nitrocarburized plate were performed at contact pressures typical for bending machines. Evaluation of wear was performed by white-light interferometer with measurements of the wear-scar topography and a subsequent calculation of the average wear depth. A strong influence of the nitrocarburizing process on friction and wear behaviour was observed. This behaviour could be correlated with the microstructure of the compound layer.