Helmuth Sarmiento Klapper

Pitting Corrosion Resistance of CrMn Austenitic Stainless Steel in Simulated Drilling Conditions—Role of pH, Temperature, and Chloride Concentration

Austenitic stainless steels have been used for many years in components for drilling equipment. These stainless steels are predestinated to meet the demanding requirements in terms of mechanical, m...

Hydrogen embrittlement: the game changing factor in the applicability of nickel alloys in oilfield technology

Precipitation hardenable (PH) nickel (Ni) alloys are often the most reliable engineering materials for demanding oilfield upstream and subsea applications especially in deep sour wells. Despite their superior corrosion resistance and mechanical properties over a broad range of temperatures, the applicability of PH Ni alloys has been questioned due to their susceptibility to hydrogen embrittlement (HE), as confirmed in documented failures of components in upstream applications. While extensive work has been done in recent years to develop testing methodologies for benchmarking PH Ni alloys in terms of their HE susceptibility, limited scientific research has been conducted to achieve improved foundational knowledge about the role of microstructural particularities in these alloys on their mechanical behaviour in environments promoting hydrogen uptake. Precipitates such as the γ′, γ′′ and δ-phase are well known for defining the mechanical and chemical properties of these alloys. To elucidate the effect of precipitates in the microstructure of the oil-patch PH Ni alloy 718 on its HE susceptibility, slow strain rate tests under continuous hydrogen charging were conducted on material after several different age-hardening treatments. By correlating the obtained results with those from the microstructural and fractographic characterization, it was concluded that HE susceptibility of oil-patch alloy 718 is strongly influenced by the amount and size of precipitates such as the γ′ and γ′′ as well as the δ-phase rather than by the strength level only. In addition, several HE mechanisms including hydrogen-enhanced decohesion and hydrogen-enhanced local plasticity were observed taking place on oil-patch alloy 718, depending upon the characteristics of these phases when present in the microstructure. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

Susceptibility to Pitting Corrosion of Nickel- Based Alloy 718 Exposed to Simulated Drilling Environments

As a result of their appropriate mechanical and non-magnetic properties, Alloy 718 (UNS N07718) has been used in directional drilling tools, particularly in applications where superior corrosion re...

Assessing the Pitting Corrosion Resistance of Oilfield Nickel Alloys at Elevated Temperatures by Electrochemical Methods

Nickel alloys are broadly used in upstream oil and gas applications as a result of an advantageous set of properties including high mechanical strength accompanied by good ductility and toughness, ...

Localized Corrosion Characteristics of Nickel Alloys: A Review

There are a great variety of commercial nickel alloys mainly because nickel is able to dissolve a large amount of alloying elements while maintaining a single ductile austenitic phase. Nickel alloys are generally designed for and used in highly aggressive environments, for example, those where stainless steels may experience pitting corrosion or environmentally assisted cracking. While nickel alloys are generally resistant to pitting corrosion in chloride-containing environments, they may be prone to crevice corrosion attack. Addition of chromium, molybdenum and tungsten increases the localized corrosion resistance of nickel alloys. This review on the resistance to localized corrosion of nickel alloys includes specific environments such as those present in oil and gas upstream operations, in the chemical process industry and in seawater service.