Laser nitriding of titanium by solid state diffusion of nitrogen at constant temperature

Abstract

Nitriding titanium during laser irradiation in nitrogen atmosphere, by solid state diffusion, was studied.A 10 × 10 mm workpiece was illuminated by a CW CO2 laser beam. A uniform beam intensity distribution was obtained with a kaleidoscope, and constant temperature during laser treatment was insured by a real time feedback actuating laser power. Surface temperatures were measured with an optical IR pyrometer focused on the sample surface. Nitriding was conducted in purified nitrogen at atmospheric pressure in a vacuum chamber at 1200°C.Optical and electronic microscopy examination of the nitrided samples showed a structure consisting with a nitrided layer of 20 to 70 µm of thickness. Microhardness measurements revealed an increase of surface hardness that reached 4000 Hv(50g). X-ray diffraction examination, under low glancing angles, showed the presence of TiN-δ and Ti2N-e phases. The diffusion profiles of nitrogen were determined by nuclear microprobe analysis. Wear tests (pin on disc test) showed a significant improvement of the wear behaviour.Nitriding titanium during laser irradiation in nitrogen atmosphere, by solid state diffusion, was studied.A 10 × 10 mm workpiece was illuminated by a CW CO2 laser beam. A uniform beam intensity distribution was obtained with a kaleidoscope, and constant temperature during laser treatment was insured by a real time feedback actuating laser power. Surface temperatures were measured with an optical IR pyrometer focused on the sample surface. Nitriding was conducted in purified nitrogen at atmospheric pressure in a vacuum chamber at 1200°C.Optical and electronic microscopy examination of the nitrided samples showed a structure consisting with a nitrided layer of 20 to 70 µm of thickness. Microhardness measurements revealed an increase of surface hardness that reached 4000 Hv(50g). X-ray diffraction examination, under low glancing angles, showed the presence of TiN-δ and Ti2N-e phases. The diffusion profiles of nitrogen were determined by nuclear microprobe analysis. Wear tests (pin on disc test) showed a sign...