Metal surface layer treating method, metal assembly and electronic device

Patent metadata

Field	Value
Publication number	US-12378664-B2
Application number	US-202217703385-A
Country	US
Kind code	B2
Filing date	Mar 24, 2022
Priority date	Sep 27, 2021
Publication date	Aug 5, 2025
Grant date	Aug 5, 2025

Abstract

The disclosure provides a metal surface layer treating method, a metal assembly and an electronic device. The metal surface layer treating method includes: putting metal into a vacuum chamber, and vacuumizing the vacuum chamber to a first vacuum degree; adding a mixed gas of acetylene, nitrogen and hydrogen into the vacuum chamber; and heating the vacuum chamber to a temperature above an ambient temperature. In response to the temperature in the vacuum chamber reaching a first temperature value above the ambient temperature and a gas pressure of the vacuum chamber reaching a first pressure value, performing glow discharge so that a carbon-nitrogen gradient hardening layer is formed on a surface layer of the metal. The method includes removing part of a carbon layer of the surface layer of the carbon-nitrogen gradient hardening layer.

First claim

What is claimed is:

1. A metal assembly comprising:
a metal body; and
a carbon-nitrogen gradient hardening layer covering the metal body, wherein
a hardness of the carbon-nitrogen gradient hardening layer is gradually reduced in a direction from an outside surface to an inside surface thereof,
a thickness of the carbon-nitrogen gradient hardening layer is in the range of 3 μm to 35 μm, and
the carbon-nitrogen gradient hardening layer has a hardness of 896 HV0.01 to 852 HV0.01 at a distance of 0 to 5 μm from a surface thereof.

2. The metal assembly according to claim 1 , wherein a carbon-nitrogen ratio in the carbon-nitrogen gradient hardening layer is 15:1.

3. The metal assembly according to claim 1 , wherein the carbon-nitrogen gradient hardening layer has a hardness of 811 HV0.01 to 437 HV0.01 at a distance of 10 μm to 15 μm from the surface thereof.

4. The metal assembly according to claim 3 , wherein the carbon-nitrogen gradient hardening layer has a hardness of 326 HV0.01 to 229 HV0.01 at a distance of 20 μm to 25 μm from the surface thereof.

5. The metal assembly according to claim 4 , wherein the carbon-nitrogen gradient hardening layer has a hardness of 195 HV0.01 to 152 HV0.01 at a distance of 30 μm to 35 μm from the surface thereof.

6. The metal assembly according to claim 1 , wherein a thickness of the carbon-nitrogen gradient hardening layer is 20 μm, and a hardness of an outermost layer of the carbon-nitrogen gradient hardening layer is in the range of 900 HV50gf to 1000 HV50gf.

7. The metal assembly according to claim 1 , further comprising:
a housing which is at least partially ring-shaped and has the carbon-nitrogen gradient hardening layer on an outer side thereof.

8. A metal assembly comprising:
a metal body; and
a carbon-nitrogen gradient hardening layer covering the metal body, wherein
a hardness of the carbon-nitrogen gradient hardening layer is gradually reduced in a direction from an outside surface to an inside surface thereof, and
a carbon-nitrogen ratio in the carbon-nitrogen gradient hardening layer is 15:1.

Assignees

• Beijing Xiaomi Mobile Software Co Ltd

Inventors

• Liu Bing

Classifications

• G04G17/08

  Housings · CPC title

• G04B37/223

  metallic cases coated with a nonmetallic layer · CPC title

• C23C16/56

  After-treatment · CPC title

• C23C16/50

  using electric discharges {(generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34)} · CPC title

• C21D8/0257

  with diffusion of elements, e.g. decarburising, nitriding · CPC title