Abstract: In coating cemented carbide or ceramics, with thin, wear resistant layers of ceramic oxide, particularly aluminum oxide, by CVD, it has been very difficult to make sufficiently even layers and to obtain desired thickness of the layer within reasonable coating times. According to the invention an improved method utilizing a dopant selected from the group consisting of sulfur, selenium, tellurium, phosphorous, arsenic, antimony, bismuth and mixtures thereof, is now available by which a considerable increase of the growth rate of the layer as well as optimal properties regarding evenness and thickness of the layer have been obtained, making the product better suited for cutting operation.

Abstract: An improved sintered cemented carbide body and method for making same is disclosed. The improved sintered cemented carbide body contains at least one metal carbide and a binder metal, on which body there is applied at least one thin, wear resistant surface layer consisting essentially of aluminum oxide and is characterized in that at least 85% of the aluminum oxide consists of the kappa form, the remainder, which mainly constitutes the alpha form, being formed as surface portions or spots having a size of at the most 10 .mu.m, the size and the occurrence of the surface portions being so adjusted that they lie within the area AOB in FIG. 1 of the attached drawing.The body is made by a method wherein a cemented carbide substrate is contacted with a gas containing an aluminum halide and a reducing agent at high temperature, characterized in that a dopant addition of tetravalent titanium, zirconium and/or hafnium ions is added to the gas in an amount of 0.03-0.5% of the totally supplied amount of gas.

Abstract: An improved sintered cemented carbide body and method for making same is disclosed. The improved sintered cemented carbide body contains at least one metal carbide and a binder metal, on which body there is applied at least one thin, wear resistant surface layer consisting essentially of aluminum oxide and is characterized in that at least 85% of the aluminum oxide consists of the kappa form, the remainder, which mainly constitutes the alpha form, being formed as surface portions or spots having a size of at the most 10 .mu.m, .[.the size and the occurrence of the surface portions being so adjusted that they lie within the area AOB in FIG. 1 of the attached drawing..].The body is made by a method wherein a cemented carbide substrate is contacted with a gas containing an aluminum halide and a reducing agent at high temperature, characterized in that a dopant addition of tetravalent titanium, zirconium and/or hafnium ions is added to the gas in an amount of 0.03-0.5% of the totally supplied amount of gas.