Rolling Bearing Nitrogen Rich Layer Fatigue Life
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Solution Overview
Problem
Existing rolling bearings face challenges in achieving long life withstanding rolling fatigue, high anti-crack strength, and dimensional stability, particularly under increased loading and temperature conditions, while conventional carbonitriding methods lead to coarsened structures and increased retained austenite, which affects crack strength and dimensional stability.
Innovation Solution
A rolling bearing with a nitrogen-rich layer formed through carbonitriding, nitriding, or nitrogenizing, where the nitrogen content is between 0.1-0.7% and the austenite grain size exceeds 10, providing enhanced rolling fatigue life and anti-crack strength, and the heat treatment process includes secondary hardening at a lower temperature to reduce retained austenite and austenite grain size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If carbonitriding is applied to harden the surface layer and grow retained austenite, then rolling fatigue life is improved, but crack strength deteriorates due to coarsened structure
Solution Approach 1:
The invention changes the chemical composition parameters by introducing nitrogen (0.03-0.7 mass%) in addition to carbon, and adjusts hardening temperature parameters (500-650°C) to achieve a microstructure with fine grained martensite and controlled retained austenite (3-20%), thereby improving crack strength while maintaining rolling fatigue life
Solution Approach 2:
The invention creates a composite microstructure consisting of fine grained martensite matrix with dispersed retained austenite grains, where the martensite provides crack strength and the controlled austenite maintains rolling fatigue resistance, resolving the contradiction between the two properties
2Duration of action of stationary object
If carbonitriding is applied to harden the surface layer, then rolling fatigue life is improved, but dimensional stability deteriorates due to increased retained austenite
Solution Approach 1:
The invention controls the hardening temperature parameter (500-650°C) to precisely control the amount of retained austenite (3-20%), and introduces nitrogen to modify the microstructure, thereby maintaining dimensional stability while preserving rolling fatigue life through the fine grained martensite structure
3Reliability
If alloy design is applied to achieve long life, high crack strength and dimensional stability, then bearing performance is improved, but raw material cost increases
Solution Approach 1:
The invention changes the chemical composition parameters by introducing nitrogen (0.03-0.7 mass%) and controlling carbon content (0.95-1.10 mass%), along with other alloying elements, to achieve the desired microstructure and properties through compositional modification rather than extensive alloying, thereby improving reliability while controlling material cost
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 significantly improves rolling fatigue life, anti-crack strength, and dimensional stability, while maintaining surface hardness and reducing the risk of stress concentration and dimensional changes, thus addressing the limitations of conventional carbonitriding methods.
Implementation Method 1
carbonitriding is applied to the surface layer of a bearing component as by adding ammonia gas to an atmosphere RX gas at the time of hardening heating
Implementation Method 2
the grain size number of austenitic crystal grains in said nitrogen rich layer exceeds the number 10
Data Source
AI summary
A rolling bearing (10) having an outer ring (1), an inner ring (2), and a plurality of rolling elements, wherein at least one of the members, the outer ring (1), inner ring (2) and rolling elements (3), has a nitrogen rich layer and the grain size number of austenite crystal grains is in the range exceeding the number 10.