Stress Corrosion Cracking of a High-Strength Steel in Aqueous Solutions

Slow strain rate testing (SSRT) was used to evaluate the susceptibility of type 4145 (UNS G41450) steel to hydrogen embrittlement (HE) in a water-based drilling mud. Environmental variables examined included potential, pH, temperature, and the presence of zinc (Zn)- and copper (Cu)-containing thread lubricants. Additional tests were carried out in 3.5% and 27% sodium chloride (NaCl) solutions. Tests were supported by detailed scanning electron fractography and H permeation measurements. Under all environmental conditions, an excellent correlation was observed between the degree of embrittlement in SSRT and the steady-state H permeation current density (i_H). Results indicated that, up to 95°C, the degree of embrittlement increased with increasing temperature and chloride (Cl^–) concentration and with decreasing potential and pH. The degree of embrittlement was affected by the presence of metal-containing lubricants as a result of HE.