Data elements affecting bearing life and its manipulation
August 06 06:05:57, 2025
**Data Elements Affecting Bearing Life and Their Control**
Home > Bearing Knowledge > Data Elements and Their Control That Affect Bearing Life
Source: China Bearing Network | Time: June 6, 2013
Bearing life is influenced by a variety of factors that determine the performance and durability of rolling elements. The early failure modes of bearings include cracking, plastic deformation, wear, corrosion, and fatigue. Under normal conditions, fatigue is the primary cause of bearing failure. The failure of bearing components is not only dependent on service conditions but also on material properties such as hardness, strength, toughness, wear resistance, corrosion resistance, and internal stress.
The key factors affecting these properties are as follows:
1. **Martensite Carbon Content in Quenched Steel**
In high-carbon chromium steel, the initial microstructure after quenching is granular pearlite. During low-temperature tempering, the carbon content of martensite significantly affects the mechanical properties of the steel. At around 0.5% carbon, the strength and wear resistance are optimal, while the fatigue life reaches its peak at 0.55%. When the carbon content of GCr15 steel is between 0.5% and 0.56%, the mechanical properties are at their strongest. The martensite formed under these conditions is cryptocrystalline, which prevents microcrack formation during quenching and offers high strength due to its dislocation-type lath structure. This ensures the best resistance against failure for bearing parts.
2. **Residual Austenite (Ar) Content**
After quenching, high-carbon chromium steel may contain 8% to 20% residual austenite. While Ar can improve toughness, excessive amounts can reduce hardness and fatigue life. Studies show that when the Ar content reaches about 17%, hardness peaks, while the touch fatigue life peaks at around 9%. However, under high loads, increased Ar can lead to more plastic deformation, reducing the bearing's life. It is important that Ar remains stable; if it transforms into martensite, the steel becomes brittle.
3. **Undissolved Carbide Distribution**
The amount, size, and distribution of undissolved carbides in hardened steel affect bearing performance. These carbides, being hard and brittle, can cause stress concentration and crack propagation, reducing the bearing’s fatigue resistance. Proper control of carbide size and distribution is essential. Reducing excess undissolved carbides improves mechanical properties and enhances bearing life.
4. **Residual Stress After Heat Treatment**
Residual stresses after quenching and tempering play a crucial role in bearing performance. Compressive residual stress increases fatigue strength, while tensile stress reduces it. Controlling residual stress through proper heat treatment ensures better mechanical performance and longer service life.
5. **Impurity Content in Steel**
Non-metallic impurities and harmful elements like oxygen and sulfur negatively impact the mechanical properties of bearing steel. Higher oxygen content leads to more oxide inclusions, reducing fatigue life and strength. Managing impurity levels through advanced refining techniques is vital for producing high-quality bearing steels.
To optimize bearing life, several control methods are employed, including proper austenitizing, fine carbide dispersion, and surface treatments like carburizing or nitriding. These processes help achieve the ideal microstructure and residual stress state, ensuring maximum performance and longevity.
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This article was originally published on China Bearing Network. For more information, visit [http://www.chinabearing.net](http://www.chinabearing.net).
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