In hot concentrated caustic solutions and in some salt atmospheres, stress corrosion cracking of which stainless steel grade has been reported with transgranular cracking?

• A. Ferritic
• B. Martensitic
• C. Austenitic
• D. Precipitation Hardened

Answer: (B)

Transgranular cracking means the crack travels through the grains themselves, not along the grain boundaries. This mode is commonly seen in harder, high-strength stainless steels under harsh chemical environments. In hot, concentrated caustic solutions and in some salt-containing atmospheres, martensitic stainless steels—due to their hardened, brittle-ish martensitic matrix and relatively lower corrosion resistance compared with austenitic grades—tend to lose their protective film and become susceptible to hydrogen-assisted cracking. The combination of high tensile stress, aggressive caustic or chloride-rich environments, and the brittle-like character of the martensitic structure promotes cracks that propagate through grains, producing transgranular paths. Ferritic steels and austenitic steels have different susceptibility patterns in these conditions and are less consistently associated with this specific transgranular cracking behavior, while precipitation-hardening grades are martensitic in nature and share this vulnerability, but the observed transgranular SCC in these environments is most characteristic of martensitic stainless steels.