1990 年 34 巻 6 号 p. 1235-1246
Nitrides used in this experiment are h-BN, A1N and Si3N4. The feasibility of using the nitrides was studied as wax pattern coating materials for a Co-Cr alloy in an atmosphere of argon. Wax patterns were painted with the nitride coating material (first investing), and then it was outer-invested with a mixture of gypsum-bonded investment and water (second investing). The temperature of mold was 700°, and the thin specimens were cast with an argon arc vacuum-pressure casting machine in the Co-Cr alloy (composition Co: 63 wt%, Cr: 27, Mo: 5, Bal.: 5; melting point: 1, 380°). Surfaces of cast specimens were investigated with the unaided eye, a scanning electron microscope, a surface roughness analyzer, an X-ray diffractometer and a micro-Vickers hardness tester.
Furthermore, the cast clasp using an h-BN coating material were made and investigated with the unaided eye.
Results were summarized as follows:
1. The nitrides inhibited remarkably a reaction between the cast specimen and the investment.
2. BN had the good effect of separation.
3. The cast surface coated BN had less clinging than uncoated one. This indicated that cleansability and work efficiency were improved.
4. The surface roughness (Rz) of the specimens decreased to 32, 42 and 60% of the control with BN, Si3N4 and A1N, respectively.
5. A hardness change of the alloy by casting was the least in the case of using BN.
6. BN also had the effect in fabricating a cast clasp in the clinical form.