Verschleißschutz durch Laserbeschichten mit wolframkarbidverstärkten Hartlegierungen

Highly stressed metal forming tools require surface layers with high resistance to abrasive wear, impact and thermoshock. A new, useful technique for producing protection layers for complex load conditions is laser cladding with carbide reinforced hard alloys. In the present work, powder mixtures of WC/Co agglomerated carbide and WC/W2C melt carbide, combined with a self fluxing Ni-alloy, are clad onto tool steels. By using optimised process parameters, a repeatable composite coating free of pores, 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 provides good perform ance also under conditions including fatigue or impact. The layers are characterised by a strong metallurgical bonding to the substrate. Examples of forming dies, laser clad with carbide containing composites, are shown in the paper.