Vacuum Surface Treatment of Metallic Materials
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Solution Overview
Problem
Existing surface treatment methods for metallic materials, such as carburizing and nitriding, face issues like internal oxidation, surface decarburization, poor controllability, high costs, and surface contamination, which affect the hardness and fatigue resistance of treated components.
Innovation Solution
A surface treatment method involving cleaning and heating metallic materials in a vacuum furnace with a mixed gas of oxygen and an inert gas to form a gradient distribution of oxygen, enhancing surface hardness while removing the oxide layer to prevent brittleness and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carburizing or nitriding is used to strengthen the surface, then surface hardness is improved, but internal oxidation and surface decarburization occur causing pockmarks and reduced fatigue strength
Solution Approach 1:
The patent applies vacuum heating to create an inert environment during surface treatment. By removing oxygen from the heating atmosphere through vacuum conditions, the harmful oxidation and decarburization reactions are prevented while still allowing carbon or nitrogen to be introduced into the surface layer for hardening.
Solution Approach 2:
The patent changes the atmospheric parameters from conventional oxidizing atmospheres to vacuum conditions. This parameter change eliminates oxygen presence during heating, preventing oxidation and decarburization while maintaining the ability to achieve surface hardening through controlled carbon or nitrogen diffusion.
2Strength
If conventional carburizing atmosphere is used, then surface strengthening is achieved, but heating furnace requires periodic cleaning due to serious pollution
Solution Approach 1:
The patent replaces conventional carburizing atmospheres that decompose and pollute the furnace with a vacuum environment. This eliminates the source of pollution while maintaining the surface strengthening effect through controlled diffusion of carbon or nitrogen in the absence of oxygen.
3Strength
If surface nanocrystallization through severe plastic deformation is used, then surface hardness and wear resistance are improved, but controllability of gradient structure is poor and depth of strengthening layer is limited
Solution Approach 1:
The patent replaces severe mechanical plastic deformation with a thermal-diffusion process under vacuum. This substitution allows for better controllability of the strengthening layer depth and gradient structure through parameters like temperature, time, and gas composition, while achieving similar or superior surface hardening effects.
4Quantity of substance
If nitridation process is used, then nitrogen content at surface is increased, but treatment time is long and nitridation layer is thin due to limited solubility and low diffusion rate
Solution Approach 1:
The patent changes the thermodynamic parameters by conducting nitridation under vacuum conditions with controlled nitrogen partial pressure. This allows for enhanced nitrogen diffusion rates and increased surface solubility, achieving adequate nitrogen content in shorter treatment times compared to conventional atmospheric nitridation.
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 significant surface hardening with improved controllability and reduced costs, suitable for mass production, and prevents surface cracking by eliminating the oxide layer, resulting in enhanced wear resistance and fatigue life.
Implementation Method 1
heating temperature is larger than a destruction temperature of a dense and native oxide at the surface of the initial metallic material
Implementation Method 2
adjusting a vacuum degree inside the heating furnace to a preset value under a protection of a mixed flowing gas of oxygen and an inert gas
Data Source
AI summary
A surface treatment method of metallic materials provided by the present invention includes steps of: (S1) cleaning a surface of an initial metallic material to be treated, and then drying; and (S2) placing the dried metallic material in a heating furnace, adjusting a vacuum degree inside the heating furnace to a preset value under the protection of a mixed flowing gas of oxygen and an inert gas, heating and preserving, cooling to room temperature by furnace cooling, and completing the surface treatment of the metallic material to be treated, wherein the heating temperature is larger than the destruction temperature of the native oxide at the surface of the initial metallic material. The present invention is able to increase the surface hardness of the metallic material within a large depth, and has the advantages of low processing cost, high efficiency, good controllability, convenient operation and low surface contamination for the workpiece.