Deposition of adherent hard coatings on steel by plasma-enhanced CVD

Abstract

Wear resistant TiN x - and TiC x N y -layers were deposited on various pretreated steel substrates in the temperature range 673–773 K. The influence of the process parameters and substrate pretreatment on the deposition rate, layer composition, interface and layer structure, microhardness and stress have been investigated. With optimized process parameters, layers with a low oxygen and chlorine impurity content, high microhardness and a good adhesive strength are obtained. Usually, the TiN x - and also the TiC x N y -layers with low carbon content deposited at 773 K have a columnar structure with a 〈200〉 texture. Nevertheless for TiC x a 〈111〉 texture is observed. TiN x -layers prepared below 773 K have a 〈111〉 preferred orientation or they are textureless. The adhesion of the coatings on plasma nitrided steel substrates is remarkably higher than on non-nitrided substrates. The critical loads for nitrided and non-nitrided S6-5-2 steel are 44 N and 14 N, respectively.