Transmission Shaft Surface Structure for Lean-Lubrication Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for extending the service life of transmission shafts in harsh environments with foreign objects and lean lubrication, such as carbonitriding and shot peening, are either insufficient or complicate the manufacturing process.
Innovation Solution
A transmission shaft with a base material of chromium steel or chromium-molybdenum steel, featuring a diffusion layer with iron carbide, iron nitride, or iron carbonitride crystal grains and a triiron tetraoxide film on its surface, which enhances surface durability and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If general carbonitriding treatment is applied to extend service life, then surface hardness is improved, but service life is still insufficient under harsh conditions
Solution Approach 1:
The invention creates a composite surface structure consisting of a diffusion layer with iron carbide, iron nitride, or iron carbonitride crystal grains embedded in a martensite matrix, combined with a triiron tetraoxide film coating. This composite structure provides both the hardness needed for wear resistance and the protective film for extended service life under harsh conditions with foreign objects and lean lubrication.
Solution Approach 2:
The invention applies local quality enhancement by creating a diffusion layer specifically on the surface of the shaft with controlled crystal grain distribution and size (average grain size ≤ 8 μm for prior austenite, ≤ 0.3 μm for compound grains). The triiron tetraoxide film is applied specifically on the raceway surface where contact with needle rollers occurs, providing localized protection where it is most needed.
2Reliability
If shot peening is used to form hardened layer and compressive residual stress, then surface durability is improved, but manufacturing process becomes complicated
Solution Approach 1:
The invention merges the hardening function and protective coating function into a single integrated process. The carbonitriding treatment creates the hardened diffusion layer with appropriate crystal structure, and the triiron tetraoxide film is formed directly on this surface through chemical conversion treatment, combining multiple functions (hardening, protection, lubrication retention) into one manufacturing sequence rather than requiring separate shot peening and coating operations.
Solution Approach 2:
The invention changes the surface properties through controlled carbonitriding parameters (temperature ≥ 930°C, atmosphere composition with ammonia) to achieve specific crystal grain sizes and phases in the diffusion layer. The triiron tetraoxide film thickness is controlled at 1-2 μm through chemical conversion treatment parameters, providing the desired protection without requiring complex multi-step processes.
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 solution extends the service life of the transmission shaft with a simpler manufacturing process, improving surface damage resistance and fatigue strength while maintaining structural integrity under adverse conditions.
Implementation Method 1
a component including a steel material is subjected to heat treatment (carbonitriding treatment) in a carbonitriding atmosphere containing ammonia (NH3) to increase the amount of retained austenite and the concentrations of carbon and nitrogen on the surface
Implementation Method 2
a diffusion layer including crystal grains of at least one of iron carbide, iron nitride, or iron carbonitride
Implementation Method 3
The triiron tetraoxide film is formed on the surface of the base material
Data Source
AI summary
This transmission shaft is used in a transmission and has a raceway surface on which needle rollers roll. The transmission shaft includes a base material and a triiron tetraoxide film. The base material includes any one of chromium steel, chromium-molybdenum steel, or nickel-chromium-molybdenum steel, and has, on a surface thereof, a diffusion layer including crystal grains of at least one of iron carbide, iron nitride, or iron carbonitride. The triiron tetraoxide film is formed on the surface of the base material and is disposed at least on the raceway surface.