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In the past decade high power, reliable, carbon dioxide lasers have become commercially available. Laser glazing is a process in which a focused laser beam is used to melt a very small portion of a component. As the beam moves away from the melted region, the underlying mass of the component causes the liquid pool to rapidly solidify. A major advantage of laser glazing is that the refined structure is only created in areas where high load carrying capacity is required
Initially rods manufactured from BG 42 and M 50 steels were laser glazed. Laser glazing transformed the normal, fine grain, martensitic steel matrix into a very fine dendritic microstructure. The carbides in the laser glazed material were greatly reduced in size due to very rapid solidification. Using a standard ball / rod rolling contact fatigue tester, enhanced rolling contact fatigue life was realized from the laser glazing process.
LM 12749 tapered roller bearing cones were fabricated from M 50 high speed steel and laser glazed. At 200% catalog load, the L15.9% life of the laser glazed M 50 bearings was 370% greater than the wrought cones. Similarly, when tested at 300% catalog load, the laser glazed bearings had L15.9% life 580% greater than the wrought cones.
Laser processing has been applied to 440 C stainless steel. In this alloy similar reduction in the size and distribution of large chromium carbides was achieved. The glazed 440 C was approximately 20 Knoop hardness points higher than the wrought alloy. Examples and properties of glazed microstructures in ball bearings and other alloy systems are discussed.
laser glazing, rolling contact fatigue, bearing life, high speed steel, martensitic stainless steel, carbide distributions
Research Specialist, The Timken Company, Canton, OH