Struktur und Verschleißeigenschaften von Hartstoffbeschichtungen

Many applications in machine building require surface layers whose wear properties are comparable with those of sintered hard metal. One technique for solving this problem is laser cladding with a powder mixture of carbide particles and a ductile metal binder. In the present work, powder mixtures of WC/Co agglomerated carbide and WC/Wsub2C melt carbide, combined with a self fluxing Ni-alloy and Stellite 21, are clad onto a low carbon steel. By using optimized process parameters, a repeatable composite coating free of cracks and with low iron dissolution can be reached. The typical structure shows a homogeneous distribution of coarse, non-melted carbide particles within the metallic matrix alloy. The carbide content is up to 50 volume percent. Large-scale investigations on the wear behaviour show that the wear resistance of laser clad coatings comes close to that of classical, sintered hard metal WC/Co. In contrast to sintered hard metal, these coatings have a higher toughness, which pr ovides good performance also under more complex loading conditions including impact or thermoshock.