Abstract
The effect of laser surface hardening on hydrogen permeability through AISI 1045 steel was measured and determination of the contribution of compressive stresses to this effect was attempted. Metallography and micro hardness measurements of the heat affected zone were performed to determine the depth of the most hardened zone. It was found that the steady state permeability of hydrogen through steel was reduced from 1·19 x 10-6 A cm-2in a normalised condition to 0·38 x 10-6 A cm-2 for a laser hardened specimen. But when compressive stresses in the hardened layer were relieved by cutting the layer off, the permeation rate of hydrogen increased to 1·74 x 10-6 A cm-2. After correctionfor the effect of membrane thickness on steady state permeability, and analysis of the effective diffusivity using Fick s first diffusion law, it was concluded that the effect can be attributed to compressive stresses in the hardened layer. It was also found that martensite reduces the effective diffusivity of hydrogen but does not affect steady state hydrogen permeability.
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