The material factors affecting the service life of KOYO bearing

Early failure forms of rolling KOYO bearing, mainly has broken, plastic deformation, wear, corrosion and fatigue, is mainly contact fatigue under normal conditions. KOYO bearing failure in addition to the service condition of the parts, mainly by the steel hardness, strength, toughness, wear resistance, corrosion resistance and internal stress state. The main internal factors affecting these properties and the state has the following several. 1. 1 the martensite hardened steel high carbon chromium steel original organization of spheroidal pearlite, in the condition of quenching temperature tempering, quenching martensite carbon content, significantly influence the mechanical properties of the steel. Strength and toughness in 0. The contact fatigue life of around 5%, 0. About 55%, crushing resistance at 0. About 42%, when the GCr15 steel quenching martensite content of 0. 5% ~ 0. 56% when, can obtain the comprehensive mechanics performance of the strongest ability to resist failure. It should be pointed out that, in this case the martensite is cryptocrystalline martensite, measured carbon content is average carbon content. In fact, the carbon content of martensite in the micro zone is uneven, near around carbide carbon concentration is higher than from carbide parts original ferrite, so they began to occur martensitic transformation temperature is different, thus inhibiting the martensite grain grew up and display in the form of microscopic cryptocrystalline martensite. It can avoid the high carbon steel quenching microstructure of the crack, and the substructure for strength and toughness are high dislocation type plate strip martensite. Therefore, only when the high carbon steel quenching for carbon in cryptocrystalline martensite KOYO bearing parts can obtain the best matrix failure resistance. 2 the retained austenite in high carbon chromium steel quenching steel after normal quenching can contain 8% ~ 20% Ar ( Retained austenite) 。 Ar has both advantages and disadvantages of KOYO bearing parts, in order to promote the beneficial and abolish the harmful, Ar content should be appropriate. Due to the amount of Ar is mainly associated with austenitizing quench heating conditions, how much it would affect the carbon content of quenched martensite and the amount of soluble carbide, difficult to correctly reflect the effects of Ar content on mechanical properties. Therefore, the fixed condition of austenite, the use of austenitic body thermal stabilization process, in order to obtain different Ar amount, in this study the quenching temperature Ar content of GCr15 steel after tempering hardness and contact fatigue life. Along with the increase in austenite content, hardness and contact fatigue life with increased to peak and then subsequently and reduce, but the peak value of Ar content is different, hardness peak appeared at about 17% Ar, peak appeared at about 9% and the contact fatigue life. When the test load is reduced, because the Ar amount increased to reduce the influence of contact fatigue life. This is because when there is not much Ar amount of strength to reduce the impact is not big, and the toughening effect is more obvious. Because the load is small, the Ar in a small amount of deformation, both to reduce the stress peak, and has the deformation Ar processing reinforcement and stress and strain induced martensite phase transformation and reinforcement. But if the load is big, Ar larger plastic deformation, and matrix, the local stress concentration and fracture thus reduce life. Should point out that the Ar the favorable effect must be under Ar a stable state, if the spontaneous into martensite, will make the steel toughness reduced sharply and embrittlement. 1. 3 quenching