Abstract: Effect s of subst rate temperature on flattening morphologies of NiCrCoAlY and zirconia droplets in plasmaspraying metal mat rix composites were studied by analyzing and comparing SEM micrographs. The result s showthat when depositing on the non-preheated polished stainless steel subst rate , the NiCrCoAl Y splat s are in disk-likeshape with piled edges and splashed fragments , which have inevitably influence on the following flattening droplets.If the subst rate is preheated up to 200 ℃, the piled edges and splashed fragments within NiCrCoAl Y splatsdecrease , and the flattening behavior of the following droplet s is improved. The zirconia splat morphology on thenon-preheated polished stainless steel subst rate is round in shape with crack and finger prolongation. The number ofcracks and finger prolongations reduces correspondingly with increasing the subst rate temperature. Furthermore ,when the subst rate is preheated up to 200 ℃, NiCrCoAlY coating porosity changes unapparently while the zirconiacoating porosity reduces profoundly.