Chemically Assisted Surface Enhancement, or CASE, is an isotropic superfinishing process which has been developed as a metal surface treatment to provide components with excellent bending and contact fatigue strength, together with resistance to high loading.

With isotropic superfinishing, a component is firstly shot peened, to create multiple indentations in the surface using the spherical shot media from which it draws its name. 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-related tensile residual stresses. This proven technique makes the surface resistant to crack initiation and propagation. 

Secondary processing by further shot peening (or dual peening) at a lower intensity with modified shot size will have the effect of reducing surface roughness and increasing the compressive stress and cold working of the near surface.

Final processing is then carried out in a controlled and gentle manner using non-abrasive finishing stones together with oxalic acids: here, the most positive or peak surface areas are progressively removed, producing a mirror-like surface finish with an extremely low surface roughness.

Some of the most common applications for isotropic superfinishing by Metal Improvement Company include the manufacture of gears, transmission shafts, bearings, cams and cam followers, journals, seal faces etc. Key benefits of isotropic superfinishing include achieving the optimum surface roughness and stress characteristics, being able to produce mirror-like finishes, the reduction of contact/surface fatigue and the prevention of micro and macro pitting. CASE is just one of many surface finishing options available by Curtiss-Wright Surface Technologies.  

For more information visit www.cwst.co.uk