Hastelloy G alloy has good high temperature strength and oxidation resistance. The hardness and tribological properties of the alloy surface can be improved through the laser nitriding process under a controlled environment. Laser gas assisted surface nitriding of Hastelloy G alloy is carried out using a CO2 laser. Temperature and stress fields in the nitrided layer are modeled using the finite element model. Metallurgical and morphological changes in the nitrided region are examined using SEM, energy dispersive spectroscopy, and X-ray diffraction. It is found that a uniform nitride layer is formed in the surface region of the workpiece and the depth of the nitride layer extends over 40 mu m below the surface. The nitride layer is free from cracks and surface abnormalities such as cavity and pores. (C) Copyright 2011 John Wiley & Sons, Ltd.