Laser nitriding: A promising way to improve the cavitation erosion resistance of Ti-6Al-4V

This paper reports on a comprehensive study of the microstructure, hardness, crack, sensitivity and cavitation erosion resistance of Ti-6Al-4V laser nitrided under different gas atmospheres containing nitrogen concentrations between 0 % and 25 %. By varying the nitrogen content of the gas atmosphere the structure and hence the hardness and cavitation erosion behaviour of the laser nitrided layers can be controlled in a wide range. The study revealed that the achieved increase of hardness and cavitation erosion resistance can be mainly attributed to solid solution hardening by nitrogen and not to the formation of titanium nitrides. Evidently, the formation of brittle titanium nitrides must be prevented in order to achieve laser nitrided layers which exhibit a low crack sensitivity and a high cavitation erosion resistance.