Laser-alloying of a titanium alloy with a nitrogen jet

Ti-6V-4A1 alloy was laser-alloyed with a CW-CO₂ laser and a nitrogen gas jet impinging at an angle of 45°. The alloyed layer was examined by means of optical and electron microscopy. The nitrogen concentration in the laser-treated zone, determined by point and line scan EDS analysis, was found to consist of 60-100 μm long dendrites with a preferred orientation along the temperature gradient. The nitrogen concentration in the dendrites-30-40At%-affected the microhardness of the laser-alloyed layer (1000 HV-1100 HV), as against 340 HV of the base material. The uniform distribution of nitrogen resulted from the very intensive mixing in the melt pool.