| Abstract Scope |
Alloy 17-4PH is PH martensitic stainless steel with short-comings for Oil & Gas applications, yet it is widely used for well services. In common to other load-bearing alloys, its tribological properties are limited, requiring use of surface hardening processes by diffusion or using adherent hard coatings. This investigation explores 17-4PH in highly soured conditions when nitrided through various processes, solution plated (Ni-11%P, Ni-Co-P), tungsten carbide, or DLC vapor deposited. Though immersion tests of various durations (2-5 weeks in up to 1500psi H2S at 4000psi), the 17-4PH surface is found to be relatively resistant to the environment while many surfaces experience various forms of damage. Mechanisms of weight-loss and/or localized corrosion are explained based on optical, SEM, and EDS analyses, all complementing macroscopic and weight-loss measurements. In turns, this investigation clarifies best practices for stainless steels outside the scope of environmentally assisted cracking, the normal limiting factor for 17-4PH. |