Influence of additive manufacturing by laser powder bed fusion on the susceptibility of Alloy 718 to hydrogen embrittlement

Abstract

The susceptibility of additively manufactured (AM) and heat-treated Alloy 718 to hydrogen embrittlement was compared to that of wrought Alloy 718. Specimens were prepared from laser powder bed fusion (LPBF) coupons built with the long axis in the x-direction (horizontal printing) and with the long axis in the z-direction (vertical printing). Despite the heat treatment, coupons printed horizontally demonstrated retained elongated grains parallel to the build, z-direction, while the coupons printed vertically had a relatively uniform and small grain structure perpendicular to the build direction, but a highly elongated grain structure parallel to the build direction. Slow strain rate testing under standardised cathodic charging conditions in 0.1 M H₂SO₄ indicated a greater susceptibility to hydrogen embrittlement of the test specimens manufactured from coupons printed horizontally, attributed to cracks more readily propagating along the elongated direction of the microstructure.