Laser Melting of Plasma Sprayed Nicocraly Coatings

Abstract

MCrAlY coatings (M = Ni, Co, Fe alone or in combination) are currently used to protect gas turbine blades and vanes from oxidation and hot corrosion. The coatings are required to be fully dense and well bonded to the substrate. They are formed either by electron beam evaporation or by low pressure plasma spraying. Another possible route is to form them by normal atmospheric plasma spraying, followed by remelting with a laser to remove porosity and other defects. The feasibility of this approach has been investigated by melting plasma sprayed NiCoCr AIY coatings on a Nimonic 75 substrate. This work focuses mainly on the effect of various laser processing parameters on the structure of remelted layers. Preliminary data on the hot corrosion properties of the laser melted coatings are also presented.