MICROSTRUCTURAL STUDY OF A COATING DEPOSI TED BY A SEMI-TRANSFERRED PLASMA-ARC TECHNIQUE AND SUBJECTED TO THERMAL CYCLIC LOADING

This work concerns a cobalt base coating, deposited by plasma torch to increase the lifetime of rolling mill rolls subject to heat fatigue T he microstruCture of the deposit was studied by optical and electronic microscopy, X diffractometry , before and after solicitation in heat fatigue. The mode of deformation of the coating in heat fatigue is the martensitic transformation. Another type of analysis, neutronic diffr action, showed the important crystallographic texture of the coating. This parameter must be taken into account since it influences the mech anical behaviour and resistance of such a coating subject to heat and mechanical solicitation.