More and more often, cemented carbides are employed for the production of wear resistant components and have to face highly demanding service conditions that combine different damage mechanisms. A key example is the range of tetraphasic (sea water, sand, liquid and gaseous hydrocarbons) flows encountered in the Oil and Gas extraction industry. Notwithstanding the importance of operating regimes of this type, the availability of fundamental and quantitative information on the corrosion performance of cemented carbides in the presence of abrasion is still limited. In this paper, we report a systematic study of the corrosion behaviour of cemented tungsten carbide grades with binders containing different amounts of cobalt (Co), nickel (Ni), chromium (Cr) and noble metal additions, subjected to controlled mechanical abrasion, impacting the stability and nature of pseudopassivation films. In this work, special attention is devoted to Cr, a classical of additive that inhibits the Ostwald ripening of tungsten carbide (WC) particles and notably improves the corrosion resistance of grades with ultrafine-to-fine WC grain size and low-to-medium binder content. We assessed the impact of binder composition on the anodic behaviour by means of linear-sweep voltammetry and chronopotentiometry as well as on the mechanical properties. The application of controlled abrasion conditions under electrochemical control is carried out with an in-house modified ASTM B611 apparatus, equipped with a three-electrode system, enabling the systematic investigation of the synergy of electrochemical and mechanical damaging conditions. Increased corrosion resistance in environments without and with added chloride—both in the absence and in the presence of abrasion—was observed in all the Co- and Ni-based grades to which growing quantities of Cr were added. Moreover, doping with ruthenium (Ru) further enhances corrosion resistance. Regarding corrosion in the presence of abrasion, the addition of Cr and Ru increases the ability of regenerating the pseudopassivation film. The optimized compositions of the binder have been highlighted that open up attractive opportunities of improved service behaviour and deployment in new applications.

Recycling of hardmetal scrap is strategic for critical raw materials recovery. Available recycling processes are polluting and have a large carbon footprint. Attempts to exploit controlled corrosion failed in industrial practice, owing to self-limiting processes. We revisit the corrosion route, in view of gaining the fundamental knowledge enabling high-throughput recovery. We selected the worst-case approach of highly corrosion-resistant CoNiWC-based hardmetal grades and neutral aqueous electrolyte at room temperature. Systematic electrochemical measurements, UV–Vis spectroscopy and SEM microscopy disclosed that, even though there is no hope to overcome the self-limiting corrosion rate, nevertheless, by exploiting the mechanical action of anodic O₂ evolution acting precisely at the interface between the residual active material and the corrosion film, the latter can be efficiently removed, periodically reactivating the hardmetal corrosion in a way that results in an ultra-high scrap destruction rate, of interest for real-life industrial processes.