Effect of laser tempering of high alloy powder metallurgical tool steels after laser cladding

Abstract

The effect of tempering after laser cladding of a high alloyed powder metallurgical tool steel was studied for die repairing purposes. In particular, a high power diode laser with scanning optics was employed for tempering. The laser tempering temperature was proven to be a critical factor in improving the mechanical properties of the coatings. In order to measure and evaluate the effect of different processing parameters (mainly laser power and linear speed) on the achieved temperature, an infrared camera and a two-color pyrometer were used. The tempering effect was mainly evaluated through cross-section microhardness profiles. The microstructure of the coatings was also studied using optical and scanning electron microscope, and the volumetric fraction of retained austenite was determined by X-ray diffraction.Experimental results demonstrated that laser tempering is a useful and appealing technique to improve the hardness of laser deposited coatings of high alloyed tool steels, which is a clear advantage when large parts have to be repaired or reinforced by laser cladding.