SPONSORS OF COATINGS AND CORROSION FEATURE
SURFACE TREATMENTS FOR HIGH PERFORMANCE COMPONENTS
Contact fatigue and surface pitting of transmission components can be reduced by the removal of surface asperities; engineering a residual compressive stress profile of adequate depth and achieving a finish that retains lubricant between the contact faces. CONTROLLED SHOT PEENING This can be achieved by controlled shot peening a gear flank or gearing surface initially to modify the surface profile reducing the stress intensity of the surface finish and finally micro honing that surface to reduce the asperities generated and change the symmetry of the profile.
The intention is not to remove all of the witness of shot peening but a percentage resulting in a matrix of load bearing smooth areas interspersed with valleys for oil pockets.
Controlled Shot Peening is the bombardment of a surface with spherical particles (shot) of pre-selected characteristics to produce a predictable compressive stress of known magnitude and depth.
The action of impinging the surface yields the material in tension but further movement is restrained by the core and a surface residual compressive stress results.
SUPERFINISHING
C.A.S.E.TM superfinishing gives further life improvement to the already highly stressed parts. By reducing Ra values, and providing a negative Rsk, benefits in contact fatigue can be achieved. Transmission testing has shown that there is a consistent 200C reduction in oil temperature; this clearly indicates that there are less power losses due to friction, so the transmission is operating as the designer has envisaged.
LASER PEENING For critical components where very deep compressive stresses with low surface disruption are demanded, new
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SUMMARY
C.A.S.E.TM superfinishing of surfaces following the controlled shot peening process, tailored to suit the application, will result in an optimised residual compressive stress and surface texture. Practical experience in processing parts for various industries has shown significant improvements in contact fatigue and surface pitting. The influence of variations in manufacturing techniques can be reduced or eliminated.
Metal Improvement Company LLC (A business unit of Curtiss-Wright Surface Technologies)
www.cwst.co.uk
peening technology is required. Laser Peening, which has a proven track record in aerospace, can fulfil these greater requirements.
Laser Peening utilises the very much greater energy from the laser source to create a much deeper compressive residual stress, but without the high level of cold work and surface disruption associated with controlled shot peening.
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