Citizen Watch Company, Ltd.

Citizen Holdings Company, Ltd.

Kenji Hanai

Masahiro Sato

Takeshi Inoue

Takanori Nanya

Yoshitsugu Shibuya

Shinji Ikeda

Junji Sato

Kazumi Hamano

Yukio Tanokura

Hachirou Kushida

Yoshitugu Andou

Akira Meguro

A decorative item and method for making same, such as an exterior part of a timepiece, wristwatch band and the like, includes a basis material of stainless steel having a carburized hardened later thereon in which carbon is diffused so as to form a solid solution in which crystalline chromium carbide is not formed and at least one hard coating is deposited on the carburized hardened layer of basis material, wherein the hard coating has a surface hardness greater than that of the carburized layer.

Decorative item and process for producing the same

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&deg; 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,is formed in the surface region of the titanium or titanium alloy,The hard surface layer,comprises a first hard layer,where nitrogen atoms,and oxygen atoms,reside in solid solution, and a second hard layer,where oxygen atoms,reside in solid solution.

Titanium or titanium alloy member and surface treatment method therefor

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Tokyo, Japan

Kenji Hanai