Manufacture Technology And Failure Analysis Of Ceramic Ball Bearings

The Characteristics and foreign and domestic technology level of ceramic ball bearings is analyzed and discussed, and the manufacture technology of ceramic ball bearings, manufacture and processing technology, quality control of semifinished ceramic ball are studied systemically in this paper. The semifinished ceramic ball is manufactured in following step: granulation of Si3N4 powder mixing sintering assistant, cold isostatic shaping and atmosphere pressure sintering or hot isostatic sintering. The precision ceramic ball is processed by rough grinding, precision grinding, primary lapping, finished lapping and so on. G5 precision grade can be obtained for ceramic balls and P4 tolerance grade for ceramic ball bearings.The design analysis on ceramic ball bearing is done. Utilizing simulation dynamic model and Introducing "ring-control hypothesis", a mathematic model is setup for design optimization of ceramic ball bearings and the computer multi-target optimization and analysis on primary parameters and constructive parameters is carried out for ceramic ball bearings. Under high speed, rolling/spin ratio, staffness, life, contact stress between ball and raceway, rated load are improved evidently for the optimized bearings.The calculation method of load rating of ceramic ball bearings is researched, and formulas to calculate dynamic and static load rating are put forward for ceramic ball bearings. The contact fatigue life, high-speed performance and stiffness is analyzed experimentally. The results of contact fatigue tests show that the average life of 5/16 " -G5 Si3N4 balls is 96.60h, L10=5.6158 106 and L50 =2.4952 107, and are 1.7, 1.9, 1.7 time as that of steel ball separately. The contact fatigue life dispersion of ceramic ball is nearly same as that of steel ball. For B7005C/HQ1P4 ceramic ball bearings, characteristic life is 700h, and the basic rating life L10t of 127h, medium life are obtained in experiments. dmn is as high as 2.52 106mm r/min.The fatigue life and mode of failure is analyzed for ceramic ball bearings. Themode of failure is normally small cycle or ellipse spall for ceramic balls, continuous small ellipse shape spall for bearing rings; the mode of failure for ceramic ball bearings is similar as that of full steel bearings, both spall rather than fracture. The effect of defects on fracture in ceramic balls is analyzed. It is recognized that all of gas hollow, inclusion, crack, layering and processing deflects may result in forming residual stress, local stress concentration and micro-crack, which cause ceramic ball to fracture under applied stress in use, and badly decrease the reliability of ceramic ball bearings.The ceramic ball bearings are widely used in different applications such as astronaut satellites, electric spindles, turbine molecule bumps and so on, and good results of engineering application are obtained. There will is wide application in chemistry, metallurgy, machinery, oil, traffic, aviation and astronaut, electron, household electric appliance, vacuum industry.