Precipitation-hardenable (PH) nickel (Ni)-alloys have been extensively used in industrial applications due to their advantageous set of properties including high mechanical strength accompanied by good ductility and toughness, excellent environmentally assisted cracking resistance, and remarkable thermal stability. Indeed, because of their non-magnetic character, PH Ni-alloys are commonly used in drillstring components including directional, measurement and logging-while-drilling tools for applications where superior corrosion resistance compared to the one delivered by traditional austenitic stainless steels is required. Recently, a Nickel – Cobalt (Co) – Chromium (Cr)-alloy with less than 1% Titanium (Ti) and minimum 2% Molybdenum (Mo) has been developed. Having high strength, primarily due to a high fraction of γ´-precipitates formed by age-hardening, this alloy owns excellent high-cycle fatigue behavior making the material ideal for drilling applications. In this study, exposure tests and electrochemical methods were used to assess the corrosion resistance of this alloy in simulated drilling environments at elevated temperatures. In addition, the obtained results were compared to those from UNS N07718 in age hardened condition. Preliminary xperimental results have shown that despite the similar Cr and Mo-contents in both alloys, these show dissimilar pitting corrosion susceptibility. A hypothesis for explaining this difference is discussed in detail.
