Effect of substrate material on the formation of thin plasma-sprayed coatings

1. It is shown that the formation of thin plasma-sprayed coatings is strongly affected by the physicochemical properties of the substrate as well as by the spraying process parameters. 2. The higher the hardness of the substrate and the lower its thermal conductivity, the larger — other things being equal — is the size of the impression of a plasma-sprayed particle on the substrate surface. Tn this process, the hardness of the substrate is the decisive factor at the instant of impact of a particle, while the thermal conductivity of the substrate plays the dominant role during the spreading of the particle. 3. A study was made of the structure of deformed tungsten drops after their solidification on various substrates. It is demonstrated that, unless recourse is had to special measures (such as preheating the substrate), microcracks are invariably generated in thin plasma-sprayed coatings.