Alloy member and method for hardening surface thereof

Patent metadata

Field	Value
Publication number	US-2019323114-A1
Application number	US-201916457938-A
Country	US
Kind code	A1
Filing date	Jun 29, 2019
Priority date	Jan 3, 2017
Publication date	Oct 24, 2019
Grant date	—

Abstract

The present disclosure relates to a titanium or titanium alloy member and to a surface hardening method for the titanium or titanium alloy member. The titanium or titanium alloy member includes a base material of titanium or titanium alloy, and at a surface of the base material, a hardened layer formed by diffusion of oxygen into the surface. The method includes: a heating step of heating the titanium or titanium alloy base material of the member to a predetermined temperature under an inert gas atmosphere; a hardening step of introducing (i) a mixed gas including an inert gas, and (ii) oxygen gas as a hardening treatment gas, to perform hardening treatment of the surface of the base material; and a cooling step of cooling the base material down to room temperature under the inert gas atmosphere.

First claim

1 . An alloy member comprising:
a base material of titanium or titanium alloy; and at a surface of the base material, a hardened layer formed by diffusion of oxygen into the surface.

2 . An alloy member comprising:
a base material of titanium or titanium alloy; and at a surface of the base material, a hardened layer formed by diffusion of nitrogen and oxygen into the surface.

3 . The alloy member according to claim 1 , wherein the hardened layer includes (i) a surface transparent oxide layer, and (ii) a diffusion layer disposed internally from the surface transparent oxide layer.

4 . The alloy member according to claim 3 , wherein the diffusion layer is thicker than the surface transparent oxide layer.

5 . The alloy member according to claim 1 , wherein
the hardened layer includes, in order inwardly from the surface of the base material, a surface transparent oxide layer, an external diffusion layer, and an internal diffusion layer, the external diffusion layer includes a portion having a hardness greater than or equal to 300 Hv , the portion being disposed internally from the surface transparent oxide layer, and the internal diffusion layer includes a portion having a hardness less than 300 Hv.

6 . The alloy member according to claim 5 , wherein the surface transparent oxide layer is thinner than the external diffusion layer and the internal diffusion layer.

7 . The alloy member according to claim 5 , wherein
a concentration of oxygen dissolved in solid solution in the external diffusion layer is higher than that in the internal diffusion layer, the concentration of oxygen dissolved in solid solution in the internal diffusion layer gradually decreases from outside towards inside.

8 . The alloy member according to claim 5 , wherein
concentrations of oxygen and nitrogen dissolved in solid solution in the external diffusion layer are higher than those in the internal diffusion layer, and the concentrations of oxygen and nitrogen dissolved in solid solution in the internal diffusion layer gradually decrease from outside towards inside.

9 . The alloy member according to claim 1 , wherein the titanium or titanium alloy member is applicable to a casing component of a wristwatch or a clock.

10 . The alloy member according to claim 9 , wherein the casing component includes a bezel, a bezel center region, a back cover, or a band.

11 . A surface hardening method for a titanium or titanium alloy member, the method comprising:
a heating step of heating a titanium or titanium alloy base material of the member to a predetermined temperature under an inert gas atmosphere, a hardening step of introducing (i) a mixed gas including an inert gas, and (ii) a hardening treatment gas including oxygen gas, at the predetermined temperature, to perform hardening treatment of a surface of the base material, and a cooling step of cooling the base material down to room temperature under the inert gas atmosphere.

12 . The surface hardening method according to claim 11 , wherein, in the hardening step, the hardening treatment gas further includes nitrogen gas.

13 . The surface hardening method according to claim 11 , wherein the hardening step includes introducing, after passage of a predetermined period after the introducing of the mixed gas, the hardening treatment gas to perform the hardening treatment.

14 . The surface hardening method according to claim 11 , wherein the hardening step includes introducing, simultaneous with the introducing of the mixed gas, the hardening treatment gas to perform the hardening treatment.

15 . The surface hardening method according to claim 11 , wherein, in the hardening step, the introducing and a stoppage of the introducing of the hardening treatment gas are repeatedly performed.

16 . The surface hardening method according to claim 11 , wherein, in the hardening step, the mixed gas includes the inert gas and hydrogen gas.

17 . The surface hardening method according to claim 16 , further comprising a hydrogen removing step of introducing, after the hardening step, the inert gas to remove hydrogen.

18 . The surface hardening method according to claim 17 , wherein the hydrogen removing step is performed at a temperature higher than the hardening step.

Assignees

• Casio Computer Co Ltd

Inventors

• Sato Junichi
• Kobayashi Kazuma
• Nagasawa Shouta
• Inoue Kenichi
• Liu Chinfu
• Liu Wuchien
• Lin Tienchai
• Kao Weipin

Classifications

• C22F1/183

  of titanium or alloys based thereon · CPC title

• C22F1/02 Primary

  in inert or controlled atmosphere or vacuum (adjusting the composition of the atmosphere C21D1/76) · CPC title

• C23C8/12

  using elemental oxygen or ozone · CPC title

• C23C8/10 Primary

  Oxidising · CPC title

• C23C8/28

  more than one element being applied in one step · CPC title