부산대학교 도서관

Disposing the titanium or titanium alloy in a vacuum vessel, and applying annealing treatment thereto by heating (a heating process); feeding a mixed gas consisting primarily of nitrogen with a trace of oxygen component into the vessel, and heating inside the vacuum vessel at temperatures in the range of 700 to 800.degree. C. in a predetermined reduced pressure condition for a predetermined length of time such that nitrogen and oxygen are diffused into the interior of the titanium or titanium alloy from the surface thereof so as to pass into solid solution therein (a hardening treatment process); and cooling the titanium or titanium alloy to room temperature after the hardening treatment process (a cooling process), are carried out. After completion of the processes described above, a hard surface layer 101 is formed in the surface region of the titanium or titanium alloy 100. The hard surface layer 101 comprises a first hard layer 102 where nitrogen atoms 104 and oxygen atoms 105 reside in solid solution, and a second hard layer 103 where oxygen atoms 105 reside in solid solution.