The influence of laser surface melting on the resistance of AISI 4135 low alloy steel to hydrogen-induced brittle fracture

Flat and cylindrical heat-treated AISI 4135 low alloy steel specimens were surface treated using power levels of 50, 100 and 200 W. The results of hydrogen permeation and slow strain rate tension (SSRT) tests show the following. 1. ser surface treatment of AISI 4135 low alloy steel results in a reduction in the hydrogen absorption kinetics as measured by the permeation test, and also an improved resistance to hydrogen-induced fracture in the SSRT test under galvanostatic charging conditions. e degree of effectiveness in reducing the hydrogen absorption rate is shown to occur at all power levels, and is greatest at the 50 W level. clear qualitative relationship is described between the hydrogen absorption rate and the time to failure in the SSRT test. This relation was even more striking in terms of the fractographic detail of the fracture face. possible explanation for the reduced hydrogen absorption as a result of low power laser surface melting treatment is the influence of the rapidly quenched metal surface on the steady state degree of hydrogen adatom coverage or the absorption kinetic rate constant or both. verse membrane permeation experiments indicated that the effect of laser surface melting on the permeation flux at constant charging current was not due to barriers in the metal which alter the hydrogen flux gradient across the membrane.