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C.A.S.E. (chemically assisted surface enhancement) is a two-stage process consisting of shot peening followed by vibratory superfinishing. The fatigue enhancement properties of shot peening are complimented with a mirror like surface finish.
Applications that require both residual compressive stress and excellent surface finish include precision gears and airfoil blade geometry. Depending on the application and customer finish requirements the valleys of peening dimples can be retained for lubricant retention.
How Superfinishing Works
Controlled shot peening is followed by chemical surface superfinishing which gently removes any metal asperities but retains valleys for optimum oil retention, reducing surface friction and operating temperatures.
How Vibratory Superfinishing Works
The component is firstly shot peened, which is a cold working process creating multiple indentations in the surface using spherical media called shot. As each indentation is made, the surface will try to yield but is restrained by the substrate, introducing a residual compressive stress and removing any prior manufacturing tensile residual stresses. This proven technique makes the surface resistant to crack initiation and propagation. The intensity and coverage of the shot peening process is carefully specified prior to any work being carried out.
Secondary processing by shot peening (dual peening) at a lower intensity and modified shot size will have the effect of reducing surface roughness. Also, increasing the compressive stress and cold working of the near surface providing additional benefit.
Final machining is then carried out in a controlled and gentle manner using non-abrasive finishing stones. It is done together with oxalic acids where the most positive or peak surface areas are progressively removed producing a mirror-like surface finish.
Applications for Vibratory Superfinishing
- Transmission gears and shafts
- Cams and followers
Key Benefits of Vibratory Superfinishing
- Optimum surface roughness and stress characteristics
- Surface reduction to mirror like finishes
- Reduced contact/surface fatigue
- Increased lubrication retention and heat transfer
- Reduction in lubricant temperature
- Reduced transmission noise
- Prevents micro and macro pitting
- Finishes suitable for microbiological cleansing and sterilization
- Good rounding ability to sharp edges for ease of handling and assembly