PURPOSE: To permit easy stripping of a thermal spraying material from a mask after thermal spraying, by forming a boron nitride coating on the part of a base substrate surface where the thermal spraying is not required to mask said part.
CONSTITUTION: BN is coated on the part 12 of the base material 1 where the thermal spraying is not required to form a BN film 2. The thermal spraying material 3 sticks uniformly on the surface of the material 1 if said material is thermally sprayed after the BN mask is formed in the above-mentioned manner. However, the thermal spraying material 3b sticking to the mask 2 part has low adhesive force and can, therefore, be easily stripped therefrom. On the other hand, the thermal spraying material 3a sticking to the part 11 where the thermal spraying is required sticks securely thereto and, therefore, said part is distinctly discriminated from the unnecessary part 12 and the film can be formed only on the necessary part 11. The BN in this case is used in the state of suspension prepd. by suspending the fine grains (0.4W1μm average grain size) of the hexagonal BN (h-BN) into a solvent at 5W30% BN content. Said BN suspension soln. is then coated on the part where the thermal spraying is not required by spray coating or by using a brush. The coating is dried after coating and the BN film which withstands use as a mask having 20W200μm thickness is formed.
SEI KOUJI
MACHIDA YOSHIO
