Graded coatings prepared by plasma spraying with Ni-coated ZrO2 powders

With Ni-coated ZrO2 powders obtained by a high-pressure hydrogen reduction process, graded coatings were Fabricated by plasma-spraying with one spray gun and a general feeder for use as thermal barrier coatings. In a first phase, the coatings were subjected to a number of tests and characterization studies, including microanalysis, microhardness test. sliding wear and scratch test. It is found that there are no distinct interfaces in the six layered coating due to the gradient changes of compositions and structures, and this structure enhances the coating cohesion significantly. Moreover, with increasing Ni content for monolithic coatings, its density increases but the microhardness decreases. Relative scratch hardness by sliding wear shows that particle reinforcement can greatly improve the wear resistance of a coating. (C) 1998 Elsevier Science S.A.