Influence of laser nitriding on mechanical and wear behaviour of high-speed steel

Abstract

Laser Nitriding is a well-known process to improve the hardness and wear resistance of steel. In this experimental work, laser nitriding was performed on high-speed steel by flowing nitrogen gas over the surface. Laser energy was used to irradiate high-speed steel surface by short laser pulses in nitrogen atmosphere. The experimental study was carried out at various processing parameters such as laser fluence (J/cm²), nitrogen flow rate (l/min) and scan speed (mm/s). The surface roughness, microhardness, and wear behaviour were measured and compared to evaluate the effect of nitriding parameters on responses. Furthermore, optimum nitriding parameters were obtained which resulted in enhancement of surface hardness by 42 % as compared to untreated samples. The wear loss was found to be decreased by 58% in the laser nitrided sample (0.0007mm3 ) as compared to the untreated sample (0.0017 mm3 ). The higher wear resistance and higher hardness were attributed to the nitride layer formed. The formation of nitride layer on the substrate material (high-speed steel tool) was confirmed using Field Emission Scanning Electron Microscopy (FESEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction analysis. Hence, laser nitriding in open environment was found to be a promising method to improve the mechanical and tribological properties of high-speed steel.