| 摘要 |
PURPOSE: To easily form a thick surface hardened layer without causing surface roughness by subjecting a titanium material to heating treatment at a prescribed temp. in an atmosphere under specified gaseous CO2 partial pressure and thereafter subjecting the same to heating treatment at a high temp. in an inert gas. CONSTITUTION: A titanium material is heated to a prescribed heating temp., preferably, to >=700 deg.C in an atmosphere in which gaseous CO2 partial pressure is regulated to >=1/20 atmospheric pressure or in an atmosphere in which CO2 partial pressure is regulated to >=1/20 atmospheric pressure, and the balance is inert gas or gaseous N2 , or a gaseous mixture thereof. Thus, O and C are infiltrated into the titanium material to harden the surface. After that, the titanium material is furthermore subjected to heating treatment at the same heating temp. or above in an inert gas or in a vacuum. Thus, the infiltrated O and C are diffused to the inside to form a thick hardened layer small in surface roughness. In the case of an (α+β) type orβtype titanium alloy material, the hardness of the base material can be increased by executing age hardening treatment after the same two stage heating treatment.
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