A work piece or structural component is coated with a system of film layers at least one of which is composed of (Al.sub.yCr.sub.1-y) X, where X=N, C, B, CN, BN, CBN, NO, CO, BO, CNO, BNO or CBNO and 0.2.ltoreq.y<0.7, with the composition within said film being either essentially constant or varying over the thickness of the film continually or in steps, as well as a process for producing it.