Super-Carburized Gear Tooth Root for Bending Fatigue Strength
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Solution Overview
Problem
Conventional super-carburized gear components face issues with the formation of a thermodynamically unstable interface between carbides and the mother phase, leading to decreased hardenability and hardness at the tooth root, which compromises the bending fatigue strength.
Innovation Solution
The gear component is made of super-carburized steel with a carbide layer on the tooth root, where the area percentage of carbides is 10% or lower and the number density is 6 pieces/10 μm2 or lower, reducing the unstable interface and maintaining hardenability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large quantity of carbides are diffused and deposited in the super-carburizing treatment, then the pitting resistance is improved, but the interface area between carbides and mother phase increases causing decreased hardenability and formation of soft structures at the tooth root
Solution Approach 1:
The patent applies different carbide characteristics to different locations on the gear component. The tooth surface is designed with a higher area percentage of carbides (5% or more) to improve pitting resistance, while the tooth root is designed with a lower area percentage of carbides (10% or less) and lower number density (6 pieces/10 μm² or less) to maintain hardenability and prevent formation of soft structures. This local differentiation resolves the contradiction between improving pitting resistance and maintaining bending fatigue strength.
2Quantity of substance
If the number density of carbides is increased to improve surface properties, then the carbide deposition is enhanced, but the concentration of alloying elements in the mother phase decreases leading to reduced hardenability
Solution Approach 1:
The patent implements location-specific carbide number density control where the tooth surface can tolerate higher carbide concentrations for improved surface properties, while the tooth root maintains lower carbide number density (6 pieces/10 μm² or less) to preserve alloying element concentration in the mother phase and maintain hardenability. This local quality differentiation prevents the depletion of alloying elements in critical regions.
3Volume of moving object
If the gear is downsized and compactified to reduce cost, then the component size is reduced, but the load on each gear increases requiring higher strength
Solution Approach 1:
The patent changes the microstructural parameters of the gear component through controlled super-carburizing treatment. By precisely controlling the carbide area percentage and number density in different regions, the patent achieves a microstructure that provides both the hardness and strength required to support increased loads in compactified gears. The tooth root specifically maintains parameters that ensure high strength despite the reduced overall gear size.
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
This approach enhances the hardness of the tooth root surface layer and improves the bending fatigue strength by minimizing the formation of softer structures like pearlite or bainite during hardening.
Implementation Method 1
the super-carburizing treatment for strengthening a component by introducing carbon at the eutectoid concentration or higher into steel and depositing a hard carbide in the martensitic mother phase
Implementation Method 2
the carburizing treatment for strengthening a component by introducing carbon into heated steel and hardening the steel at atmospheric pressure and forming a hard martensitic structure
Data Source
AI summary
This invention provides a gear component with high hardness of a surface layer in a tooth root and with the excellent bending fatigue strength. The gear component of the invention comprises a surface layer of a tooth root including a region in which the area percentage of carbides is 10% or lower and the number density of carbides is 6 pieces/10 μm2 or lower.