Cutting tool wear of laser-surface-melted high speed steels

Abstract

A continuous wave CO 2 gas laser, operating at a power of 800 W, was used to surface melt the rake and clearance faces of AISI M2 and M35 single-point lathe tools. The tool bits were then tempered at 560 °C for 2 h. The melt depths ranged from 600 to 800 μm. The surface-melted layers were subsequently ground down to 200–250 μm. A 20 h.p. engine lathe was used to turn an AISI 4142 steel workpiece using both conventionally heat-treated and laser-surface-melted tools. The results indicated that the tool life of laser-treated M2 steel was 200%–500% higher than that of conventionally hardened tools when the tool life criterion was catastrophic failure. For M35 steel, the tool life of a laser-melted tool was 20%–125% higher than that of a conventionally hardened tool when the tool life criterion was based upon flank wear (to reach a distance of 0.30 mm). The reduction in tool wear due to laser surface melting was explained as being because of the high alloy content of martensite, the fine austenite grain size and the fine dispersion of carbides, all of which resulted in high hardness, good toughness and a low coefficient of friction at the tool-chip interface.