Surface damage during machining of annealed 18% nickel maraging steel Part 2 — Lubricated conditions

Abstract

The effect of cutting speed and tool wear land length on the surface damage produced during the machining of annealed 18% nickel maraging steel under lubricated conditions was determined. Machined test pieces were examined with a scanning electron microscope and an optical microscope. Surface roughness was determined with a profilometer. The results of the investigation show that during machining fine scale surface damage in a variety of forms is produced over the range of cutting conditions used. It is suggested that the fine scale surface damage is associated with the phenomena of continuous chip formation and interaction between the tool nose region and freshly machined workpiece surface. Comparisons are made between the characteristics of surfaces machined under lubricated and unlubricated conditions. The differences are interpreted in terms of the changes produced in the frictional conditions and stress distributions at the contact surfaces between the chip, tool and workpiece by application of a lubricant. It is shown that scanning electron microscopy is more indicative of the true condition of the surface than surface roughness measurements.