BALL BURNISHING OF 316L STAINLESS-STEEL

The process of ball burnishing AISI 316L stainless steel was studied. Taguchi techniques for the statistical design of experiments were employed to establish the optimum parameters for achieving good surface finish (response) on flat specimens. An L16 (4(5)) orthogonal array was chosen to study the effects of five burnishing parameters (control factors). The roughness of the pre-burnished surface was included as a noise factor. It was found that the type of ball material, the depth of penetration, the burnishing speed and the type of lubricant significantly affect, at a 99% level of confidence, the surface finish of the burnished specimens. Feed was significant at a 96% level of confidence. The minimum roughness could be achieved using ZrO2 as the ball material, kerosene as lubricant, a depth of penetration of 20 mum, a feed of 110 mum and a burnishing speed of 300 mm/min. A confirmation test yielded an average surface finish of 1.017 mum (R(tm)), which fell within a 90% confidence interval constructed about the predicted optimum. Using this set of parameters, a 3D curved surface was similarly burnished. The curved surface was generated using the solid modeler CATIA running on an IBM 4381 P13 mainframe. Pre-burnishing milling and ball burnishing were performed in a single setting on a LeBlond Makino FNC40 vertical machining centre. Surface roughness values varying between 0.6 and 0.9 mum (R(tm)) were obtained for the curved surface.