| 摘要 |
PURPOSE:To carburize a Ti-6Al-4V alloy up to a larger depth than the conventional limit depth, by subjecting the alloy to heating from room temp. to a high temp. at a high degree of vacuum, carburization at the high temp. with a carburizing gas, reheating to a higher temp. at the high degree of vacuum and cooling with a rare gas. CONSTITUTION:A Ti-6Al-4V alloy is heated from room temp. to about 1,050 deg.C at such as a high degree of vacuum as >=2X10<-4>Torr. During the heating, the formation of a titanium oxide film is prevented by the vacuum. The alloy is carburized at the high temp. by blowing a carburizing gas such as CH4, the gas is exhausted to the above-mentioned high degree of vacuum and the alloy is heated to >=1,100 deg.C. The heated alloy is held at the temp. for a certain time and cooled by blowing a rare gas such as Ar. This method is applicable to vacuum carburization and hardening for the surface hardening of ordinary Ti-6Al-4V alloy parts such as engine valves.
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