Advances in the surface defect machining (SDM) of hard steels

• A new machining approach “surface defect machining” (SDM) was proposed.
• SDM is proposed as a pathway to bridge the gap between grinding and cutting.
• SDM was found to break the barrier of critical feed rate.
• SDM enabled achieving a machined surface roughness of Ra 30 nm.

This paper reports the realisation of precision surface finish (Ra 30 nm) on AISI 4340 steel using a conventional turret lathe by adapting and incorporating a surface defect machining (SDM) method [Wear, 302 (2013) 1124–1135]. Conventional ways of machining materials are limited by the use of a critical feed rate (experimentally determined as 0.02 mm/rev), beyond which no appreciable improvement in the machined quality of the surface is obtained. However, in this research, the novel application of an SDM method was used to overcome this minimum feed rate limitation ultimately reducing it to 0.005 mm/rev and attaining an average machined surface roughness of 30 nm. From an application point of view, such a smooth finish is well within the values recommended in the ASTM standards for total knee joint prosthesis. Further analysis was done using SEM imaging, white light interferometry and numerical simulations to verify that adapting SDM method provides improved surface integrity by reducing the extent of side flow, microchips and weldment during the hard turning process.

Finite element analysis of the surface defect machining of hard steel when the: (a) depth of surface defects is less than the depth of cut and (b) depth of surface defects is larger than the depth of cut.Figure optionsDownload as PowerPoint slide