S–O–N Composite layers improving the wear resistance of the steel

Wear resistance of the steel is one of the key parameters deciding about its applications in the industrial practice. Therefore to improve this characteristic heat-chemical treatments of the surface are widely applied. One of such treatments is nitriding, which increases significantly the hardness of the surface. The addition of sulfur to the reactive atmosphere has a second positive effect, because it reduces the frictional coefficient of the layers. In the present article, the authors present part of their investigation on the mechanism of the layer formation to explain these excellent wear characteristic of the steel after nitriding in ammonia atmosphere with the addition of 1% of SO2. It was stated that during the treatment a very complex composite layer is formed which is composed of the mixture of very soft and very hard phases. Moreover, it was also observed that the segregation of the elements from the matrix takes place and that they participate in the layer formation.