As reported previonsly, internal stress in flame sprayed procelain enamel coating is larger than that in ordinary baked coating, and by this reason, the flame sprayed porcelain enamel coating is more sensitive for mechanical and thermal schock.
In order to avoid this defect, the authors tried to improve the method of spraying and got the following results.
1. By spraying at high temperature (650-750°C), moderately thick intermediate layer is formed between base and coating and the coating is adherent and stands schock as ordinary baked coating.
2. By the addition of pyrophyllite in the flit, and by shortening the time of melting, good adherent coating is obtained. This is due to the reduction of internal stress in the coating.
3. By the application of very brittle flit as under coating, shock-resistant adherent coating is obtained. This seems to be due to cusioning action of crack in the under coating.
4. It is possible to spray porcelain enamel on the old coating. But, in this case, operator should be done with great carefulness in order to avoid crazing, chipping and fishscaling.
抄録全体を表示