Resistance Toward Hydrogen-Induced Stress Cracking of Hot Isostatically Pressed Duplex Stainless Steels Under Cathodic Protection

摘要

The resistance toward hydrogen-induced stress cracking (HISC) of forged and hot isostatically pressed (HIP) super duplex stainless steel (SDSS) according to UNS S32760 have been compared by slow strain rate testing (SSRT) under various environmental conditions, comprising exposure to a 3.5% sodium chloride (NaCl) solution, cathodic polarization to -1,050 mV vs. saturated calomel electrode (SCE), and various temperatures (4° C to 80° C) and pressures (100 bars vs. nominal 1 bar). The effect of material precharging was also investigated. The SSRT demonstrates the improved resistance toward HISC for the HIP vs. the forged material. A significant effect of precharging is seen for both materials, the effect being larger for the forged material. The effect of temperature appears to be modest at temperatures above room temperature (RT); the total fracture strain ratio vs. baseline (air at actual test temperature) for the HIP SDSS increases from approximately 0.5 at 4° C to approximately 0.7 at temperatures above RT. Evidence of secondary cracking at all temperatures confirms a susceptibility to HISC even at 80° C. The effect of pressure, also investigated for the HIP SDSS, appears to be insignificant in this short-term testing. [PUBLICATION ABSTRACT]