Effect of Base Metal on the Thermal Cycle Properties of Heat-Resistant Plasma Sprayed Coating

The authors did thermal cycle test about Al₂O₃ sprayed 1%Cr-0.5%Mo steel and 18%Cr-8%Ni steel, and compared the failure type of thermal sprayed coating in both steel. The results obtained are follows.

(1)The thermal cycle fatigue life of thermal sprayed 1%Cr-0.5%Mo steel is worse than that of thermal sprayed 18%Cr-8%Ni steel.

(2)In the case of thermal sprayed 18%Cr-8%Ni steel that is difficult to oxidize at high temperature, while thermal cycle, a tensile stress occurs in a sprayed coating and a compressive stress occurs in a substrate. So the thermal strain occurs in the interface of sprayed coating and substrate. The sprayed coating delaminates when the thermal cycles reach the limit value.

(3)In the case of thermal sprayed 1%Cr-0.5%Mo steel that is easy to oxidize at high temperature, while thermal cycle, dense oxide film occurs in the interface of  sprayed coating and substrate, and adhesive strength in the interface becomes small. So the sprayed coating delaminates under the lower thermal strain.