Secrets of C . A . S . E by Curtiss-Wright Surface Technologies
COATINGS ISOTROPIC SUPERFINISHING
CURTISS-WRIGHT
Secrets of C . A . S . E by Curtiss-Wright Surface Technologies
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
38 PECM Issue 68