Titanium Alloy Surface Hardening via Oxygen Diffusion
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Solution Overview
Problem
Conventional surface hardening methods for titanium materials, such as atmospheric thermal oxidation and vacuum thermal oxidation nitrification diffusion processing, often result in reduced luster, surface roughness, and discoloration, compromising the external appearance quality of ornamental items like luxury wristwatches and glasses frames.
Innovation Solution
A surface hardening method involving a titanium or titanium alloy base material with a hardened layer formed by the diffusion of oxygen and nitrogen, comprising a thin surface transparent oxide layer and a thicker internal diffusion layer, where the concentration of oxygen and nitrogen dissolved in solid solution gradually decreases from the surface, maintaining high surface hardness and luster while preventing discoloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If atmospheric thermal oxidation processing is used to harden the surface, then surface hardness is improved, but the finished oxide layer becomes gray colored, loses metallic luster, and becomes rough
Solution Approach 1:
The patent employs vacuum environment for thermal oxidation processing instead of atmospheric conditions. This inert environment control prevents the formation of thick gray oxide layers while allowing controlled oxygen diffusion into the titanium surface, thereby maintaining metallic luster while achieving surface hardening through controlled oxide layer formation.
Solution Approach 2:
The patent optimizes processing parameters including temperature (600-800°C), time (1-10 hours), and vacuum degree to control the thickness and composition of the oxide layer. By precisely controlling these parameters, the surface hardness is improved while the oxide layer remains thin enough to preserve metallic luster and surface smoothness.
2Manufacturing precision
If vacuum diffusion processing is performed after atmospheric thermal oxidation, then crystal grain size and surface roughness are improved, but polishing treatment becomes difficult and surface luster declines
Solution Approach 1:
The patent performs vacuum thermal oxidation processing as a preliminary treatment before any polishing operations. By controlling the oxide layer formation in vacuum conditions, the surface is pre-conditioned with fine crystal grain structure and appropriate roughness, making subsequent polishing much easier and more effective while preserving surface luster.
3Manufacturing precision
If vacuum thermal oxidation nitrification diffusion processing is used, then crystal grain size and surface roughness are improved, but the surface becomes discolored and rough when processing parameters are not skillfully adjusted
Solution Approach 1:
The patent establishes specific parameter ranges: temperature of 600-800°C, processing time of 1-10 hours, and vacuum degree control. These optimized parameters ensure uniform oxygen diffusion without excessive oxide layer formation that causes discoloration, while achieving fine crystal grain structure and improved surface roughness.
Solution Approach 2:
The patent implements monitoring and control of processing parameters during vacuum thermal oxidation to maintain optimal conditions. By controlling temperature, time, and vacuum degree within specified ranges, the process achieves consistent results with fine grain structure and uniform surface appearance without discoloration.
4Strength
If nitrogen solid solution is introduced to improve surface hardness, then surface hardness value increases, but adhesion of vapor-deposited film becomes low and surface discoloration occurs
Solution Approach 1:
The patent removes nitrogen from the processing atmosphere and relies solely on oxygen diffusion for surface hardening. This extraction of nitrogen eliminates the problems of poor film adhesion and surface discoloration associated with nitrogen-containing treatments, while still achieving the desired surface hardness through controlled oxygen diffusion and oxide layer formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves high surface hardness, maintains metallic luster, and ensures good external appearance quality by controlling the thickness of the transparent oxide layer and diffusion layers, effectively addressing the limitations of existing methods.
Implementation Method 1
a hardened layer formed by diffusion of oxygen into the surface
Implementation Method 2
a hardened layer formed by diffusion of nitrogen and oxygen into the surface
Implementation Method 3
a heating step of heating a titanium or titanium alloy base material of the member to a predetermined temperature under an inert gas atmosphere
Data Source
AI summary
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.