Aircraft engine bearing new materials

1 new aircraft engine bearing materials. M50NiL bearing steel 25 years from 1955 to 1980, the speed of the aircraft engine bearing stable growth, the dn value has reached nearly 2. 5 million. Into the ninety s, the aircraft engine high speed and high temperature puts forward higher requirements on rolling bearing. However, the existing bearing steel, even the special high temperature resistant bearing steel, such as the M50, 18 4 - 1 and 14 cr - 4 mo family of all kinds of derived type, such as the CRB - 7 and GB - 42, at significantly higher than the current engine bearing temperature can still work normally. But there is still an important restriction factor, this is hardening steel bearing ring under the condition of the ultra-high speed easy to fracture, this kind of failure occurs with little or no precursors. In order to find out a kind of both the M50 bearing steel with the performance, and disjunctive better bearing steel, the MRC SKF bearing under the support of the company in the United States air force has carried out a series of research, finally chose M50NiL. M50NiL in addition to the fracture toughness increased, compared with other high temperature hardening bearing material, the microstructure and fatigue strength are also very good. One reason is that no large particles in the M50iL carbide, therefore, this kind of steel is not sensitive to carbide caused by fatigue crack. Of an exploration M50, more easily than M50NiL raw material and material of rolling and forging a more convenient, but to get the ideal hardening layer, core microstructure and certain material properties, must be precise control of quenching and heat treatment process. As the research M50NiL processing method, SKF made great efforts, spend a lot of money. MRC technology researchers thought that heat treatment can make the material in the neighboring at raceway surface residual compressive stress, under the condition of high dn value, the stress area can be offset the effect of circumferential stress, so as to improve the bearing life. The Wilson of SKF phase control technology, can get high compressive stress, and depth of hardening three times than the traditional process. SKF has used the traditional way of M50NiL do overheating processing experiment, it is concluded that the material fracture toughness value is 275 ~ 350 mpa M1/2, when bearing the velocity to the dn = 3 million, it has good anti-crack properties. To improve the bearing rotating speed and/or produce larger surface defect, fracture toughness value is close to 700 mpa - necessary m1/2。 In order to improve the core toughness, SKF developed a process, can make the M50NiL after heat treatment without loss of surface features to get a specific core toughness. SKF, the researchers found that the technology can also improve the residual compressive stress, so as to further improve the performance and reliability of the bearing. This process includes the workpiece from the austenitizing temperature cooling to the core and surface of martensite began to form between the temperature of a temperature, and then the workpiece heated to a high temperature, and in the outer layer ( Hardening layer) Core cooling and phase change before tempering. By selecting the appropriate core tempering cycle, but the core heat treatment to the toughness and strength, and won't have too much influence on surface features. Proven, based on the selected core tempering temperature, the core hardness should be controlled in 30 ~ 45 HRC. The core of toughness