Tool life and wear behavior of CO 2 laser-alloyed carbon tool steel with tungsten

Abstract

A 1 kW continuous-wave CO 2 laser with an optical scanner was used to generate hard surface layers by surface alloying of AISI 01 carbon tool steel (CTS) with tungsten foils (25 μm thickness). The main objective of this process is to improve the cutting performance and tool life of CTS by laser technique. The rake and clearance faces of the tools were laser alloyed using two tungsten foils and four tungsten foils and then tempered at 560 °C for 2 h and reground to retain the tool geometry. Optical metallography, scanning electron microscopy and Vicker's microhardness test were employed to characterize the alloyed layers. The depth of laser-affected zones was about 700 μm and the hardness of the laser-alloyed layer was about 750 HV. Both uncoated and laser-alloyed tools were tested on a 20 HP engine lathe by turning an AISI 1045 hot-rolled steel workpiece. Machining tests of laser-alloyed tools showed a substantial improvement in tool life (about 23 ×) over uncoated tools when the tool life criterion was 0.3 mm flank wear land. The tool wear of tungsten-alloyed CTS was reduced by about 75%. Additionally, the contact length at the chip-tool interface of tungsten-alloyed tools was reduced by 78% and the coefficient of friction was reduced by 71%. The performance of laser-alloyed CTS was comparable with that of AISI M2 high speed steel tools. These results are discussed with reference to the microstructures and tool wear mechanisms.