ศึกษาอิทธิพลของกระบวนการกดรีดผิวแข็งด้วยเซรามิกบอลต่อความแข็งผิวและความเค้นตกค้างของเหล็ก SKD11

Abstract

surface layers. The process improves the surface hardness, the internal residual stress, and the surface roughness of the workpiece. Accordingly, it could be used in a wide variety of industrial application development such as ship propeller manufacturing and mold manufacturing to shorten time and reduce damages in production processes. The purpose of this research was to study the ball burnishing process of the SKD11 steel with a silicon nitride ceramic ball measuring 8 mm in diameter, the hydraulic oil pressures of 200, 400 and 600 bar, and the hardened depths of 0.3, 0.5 and 0.7 mm at the speed of 2000 mm/ min and the feed rate of 0.1 mm /rev. Then, the workpiece was examined for surface hardness, residual stress, surface roughness, and microstructure of the cross-sectional area of the burnished surface. The results revealed that both the hydraulic oil pressure and the hardened depth influenced the surface hardness of the workpiece. The average surface hardness value had a tendency to be related to the internal residual stress value at the maximum value of 629.4 MHV or 57.8 HRC at the hydraulic oil pressure of 400 bar and the hardened depth of 0.5 mm which was equivalent to the result of a heat treatment process. The surface roughness was within acceptable machining standards. The average surface hardness could be compared to the result of a treatment process. Moreover, the microstructure of the cross-sectional area of the burnished surface was densely packed, resulting in the increase of hardness and residual stress.