What cause a Bearing failure ?

- Apr 22, 2020-

What cause a Bearing failure ?

 After analyzed the damaged bearing in the failed planetary gear reducer from the aspects of the chemical composition, hardness and metallographic structure, thus we ,ZBF Bearing maunfacturer,determined the cause of bearing failure.

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1. Visual inspection

The surface of the roller has indentation, pitting and squeezing deformation marks, local peeling is damaged, and the inner ring rib is broken. There are squeezing marks on the surface of the broken and broken pieces of the outer ring, and there are circumferential processing marks on the surface of the raceway.

2. Chemical composition and hardness inspection

The inspection and test results shows that  the chemical composition of the bearing outer ring and the inner ring are in accordance with the composition of high carbon chromium bearing steel GCr15SiMn, and the roller material is in accordance with the GCr15 composition; thehardness if the bearing inner and our ring are both in the range of the requirements for bearing steel rolling bearing parts.

3. Metallographic examination

Had put the failed bearing into a low-power hot acid immersion test and the results  showed that there were dendrite segregation in the inner and outer ring steels, and central band segregation in the roller steel, which affected the mechanical properties  and also have an influence on the heat treatment and processing technology.

4.  Analysis and Results

The surface of the broken outer ring raceway has squeezing marks, and the surface of the raceway can be seen with circumferential processing knife marks, indicating that the outer ring raceway surface is rough, and there are large troughs on the raceway surface. They are like sharp corner notches and cracks. It is sensitive to stress concentration, resulting in increased contact stress with the roller cylindrical surface, affecting the performance and service life of the bearing, which is the main factor for early failure of the bearing.

 The surface of the outer ring raceway has visible circumferential machining patterns, and the rough surface causes the contact stress with the roller cylindrical surface to increase, which is the main factor for early failure of the bearing. Segregation, non-metallic inclusions and network carbides in bearing roller steel exceed the standard, which are the main factors of bearing roller failure.

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