What is the Effect of Oxides on Bearing Service Life?

Bearing steel oxides, nitrides and other complex composition of various point, spherical undeformed inclusions on the bearing life is harmful, but the degree of harm is not the same. Research on the relationship between oxide inclusions and contact fatigue life shows that: the more oxides and silicates, the lower the life, especially AlOCaO has the greatest impact on life.

Oxide on bearing life and reliability of the adverse impact is mainly due to small plastic deformation or no deformation of the oxide, as well as point, spherical inclusions easily with the bearing steel matrix organization between the interval, the destruction of the continuity of the matrix, and in the role of alternating stress, easy to produce stress concentrations in these intervals, when the stress reaches a large enough, it will produce cracks at the inclusions, thus becoming the origin of bearing fatigue spalling. Subsequently, under the further action of alternating stress, the cracks continue to expand until the bearing fails. The lower the coefficient of linear expansion of oxide inclusions, the lower the plasticity, and the more irregular the shape, the greater the stress concentration will be, resulting in a higher probability of early bearing failure. For a long time, some scholars believe that the brittle inclusions should be seen as cavities, which play a role in increasing stress, under the action of repeated alternating stress, there will be stress concentrations in these cavities, so that the microscopic stress of the surrounding material reaches a very high value, resulting in shear deformation and the formation of cracks. In addition, the study of cyclic contact fatigue mechanism of GCr15 steel concluded that: aluminosilicate pitting is not a homogeneous whole, but can be divided. Through microscopic observation it can be found that the fine dark lines on the aluminosilicate inclusions are relatively weak zones, which can easily become the origin of microscopic cracks under cyclic loading.

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