Abstract
A 5 kW continuous wave CO 2 gas laser, operating in an oscillating square beam mode, was utilized to melt inject hexagonal BN powders into the surfaces of AISI T1 and M 2 tool steels. Optical metallography, scanning electron microscopy, Auger spectroscopy and Vickers' microhardness tests were employed to characterize the melt layers. Both the hardness and the BN concentration of laser-processed layers were increased with an increase in the number of superimposing laser passes. A Vickers hardness of 2150 HV (maximum) was obtained in the specimen that was BN injected ten times. Microstructural features included fine cellular-dendritic structures and complex precipitates of metal boronitrides. The melt layers were nearly free from cracks and pores.
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