Abstract - In this work, the effect of microstructure of low alloy carbon steels on the resistance to sulfide stress cracking (SSC) was analyzed Several modified AISI 4130 steels (most of them microalloyed with V, Nb, Ti or B) were heat treated so different yield strengths and microstructures were obtained. The SSC performance was evaluated using Double-
Cantilever-Beam Test (Method D NACE TMOl77-96). According with their microstructure, the materials can be divided in three different types: materials that presented some percentage of upper bainite in their microstructure (composed of laths of approximately 1 micron wide and large carbides at the border of the laths) presented significantly lower SSC resistance. Materials which had microstructure composed mainly of tempered lath martensite had an intermediate resistance. In addition, the presence of large grain boundaries reduced the SSC resistance. The best resistance was obtained with a microstructure that is a mixed of tempered lath martensite and a phase composed of ferrite and carbides; this material presented also a fine dispersion of (CN)Nb.
Keywords: Sulfide Stress Cracking, HSLA Steel, Crack Propagation, Double Cant ilever Beam, NACE TM 0177-96. Microstructure.