Properties of plasma-sprayed chromium-nickel spinel coatings

1. The strength with which a coating of chromium-nickel spinel adheres to an OT-4 titanium alloy substrate lies in the range 1.15–1.40 kg/mm2. Preheating the surface to be coated to 450°C increases the adhesion of the coating by 25–30%. 2. The adhesion of a coating to its substrate begins to decrease appreciably after 10 thermal cycles. 3. An 80% Ni-20% Cr alloy undercoat has no effect upon the adhesion of a spinel coating and adversely affects its thermal fatigue resistance. 4. The degree of blackness (coefficient of absorption) of a spinel coating is 0.94–0.95.