Laser surface solutionizing of inconel 718: Improvement of resistance to hydrogen embrittlement Available to Purchase

While INCONEL 718 is one of the most highly utilized Ni-base superalloys, this alloy has high sensitivity to hydrogen embrittlement. Hydrogen cracking tends to occur at the surface of stress concentrated regions. A laser irradiation can locally solutionize such surface regions and reduce the hardness. Therefore, this laser surface solutionizing is effective in preventing hydrogen cracking of INCONEL 718 with little sacrifice of the strength of structures. In the present work, a 2.5kW CO₂ laser has been applied to surface solutionizing of INCONEL 718. The solutionized zones, where the age precipitates of γ′ and γ″ were dissolved in the matrix, could be obtained at the surface of INCONEL 718 without melting the treated zones by controlling the defocus distance and traverse speed. The hardness of the laser solutionized zones was reduced to below 250Hv from the base metal hardness of approximately 450Hv. The depths of the surface solutionized zones increased with the defocus distance. The surface solutionized zone with more than 1mm in depth was obtained without melting in an optimum condition. The ductility of the surface solutionized specimen was almost twice that of the base metal in a tensile test under a 29.4MPa hydrogen atmosphere at room temperature with hydrogen pre-charging.