Nickel alloy UNS N07718 (Alloy 718) is extensively used in the oil and gas industry. However, it is limited by NACE MR0175/ISO15156 which only permits use at a maximum of 200 psi (1.38 MPa) H2S partial pressure at 400°F (204°C). To expand the Stress Corrosion Cracking (SCC) safe use limit of Alloy 718, NACE TM0198 Slow Strain Rate (SSR) testing was performed first to identify an upper H2S limit (i.e., 650 psi [4.48 MPa]). NACE TM0177 C-ring testing subsequently qualified Alloy 718 at this high limit in modified NACE Level VII conditions, and also under 910 psi (6.27 MPa) H2S partial pressure in a simulated field environment (total 15 ksi [103 MPa]) based on equivalent dissolved H2S concentration. This is the highest service H2S limit reported for Alloy 718 and also evidence that validates the effectiveness of dissolved H2S concentration as new sour severity metric for Ni alloy SCC qualification.