Study of Effects of Alloying and Heat Treatment on Hydrogen Enbrittlement Susceptibility of Electroslag Remelted 4340 Steel

摘要

This program focuses on the need to improve the resistance of high-strength steels to hydrogen embrittlement of hydrogen stress cracking. Variations in heat treatment and modifications in alloy composition of electroslag remelted 4340 steel at 53 HRC were extensively explored. Target goals were established in terms of a threshold stress intensity parameter, KIscc for open circuit potential conditions, designated KIhem for cathodic charging conditions under stress during test, which were the primary test conditions in this program. In general, all alloy additions improved KIhem. The addition of 0.1% vanadium appears to be the most significant individual modification to ESR 4340 steel in that it alone provides the same gains as the more heavily alloyed ESR 4340 steels. The results must be somewhat qualified because the hardness of ESR 4340V was 50 HRC instead of the intended 53 HRC. Silicon additions of about 1.5% tended to maximize the benefits from alloy modifications. Although within an alloy system the heat treatment effects were monor or secondary relative to alloy additions, the use of an intermediate quench and subzero cooling appeared to maximize the benefits from heat treatment.