Surface layers on cobalt base alloys by boron diffusion

Boronizing is used to improve the wear resistance of the surface of metals and alloys. Various powder mixtures containing boron compounds or amorphous boron were tested at different treatment temperatures. The boronizing time was varied also. The diffusion was observed by metallography and microhardness testing of sloping cuts of the alloys; sloping cuts were necessary because of the thin boronized surface layers with different boride compositions. Borides are formed by reactions with the diffusing boron. Their structures were determined by X-ray diffraction. Separate layers containing different borides were found and the composition of some of these borides was studied. Cast cobalt base alloys and cemented carbides contain different amounts of cobalt. Since boronizing leads to the formation of mainly cobalt borides, the boronized layers of these types of alloys are different.Some examples of applications and results will be given.