Fabrication of functionally graded Fe-TiC wear resistant coating on CK45 steel substrate by plasma spray and evaluation of mechanical properties

Abstract

The main challenge in production of metal matrix composite coatings is the existence of thermal residual stress in coating – substrate interface which results in delamination of the coating eventually. The aim of this paper is to enhance the tensile bond adhesion of the coating by fabricating functionally graded coating. In this regard, raw materials including titanium carbide and iron powders were milled with different compositions. From the substrate to the surface, the weight fraction of TiC particulates increased from 25% to 100%, while the weight fraction of Fe particulates decreased in mentioned direction. Moreover to make a comparison between mechanical properties of the graded coating with those of duplex and single layer coatings, a coating system comprising NiCrAlY bond coat and 100 wt% TiC top coat and a single layer titanium carbide coating were prepared as well. X-Ray diffraction method was used to identify obtained phases from each composition. In addition, microstructural properties of the coatings were investigated by scanning electron microscope. Mechanical properties such as adhesion, hardness and wear resistance were evaluated by tensile bond test, Vicker's method and pin- on- disc method, respectively. The results revealed that the FGC sample has higher coating adhesion in comparison with other coating. Moreover the wear test results showed that the FGC sample faced with less weight loss which means higher wear resistance.