Mechanisms of erosion-corrosion on a cobalt-base alloy and stainless-steel UNS S17400 in aggressive slurries

Two materials, which are candidates in the construction of drill bits, have been studied in severe liquid-solid impingement conditions. Analysis of the weight loss was carried out on Stellite X40 (Co-base) and UNS S17400 (stainless steel) materials at 30, 60, and 90° angles of impingement under erosion-corrosion conditions at the free-corrosion potential and with applied cathodic protection. A preliminary analysis of the corrosion behavior of the materials in static conditions was the starting point for the electrochemical analysis. A more extensive corrosion analysis under erosion-corrosion conditions was carried out through direct current (DC) potentiodynamic tests with varying angles of impingement. The results were used to identify the contribution of mechanical erosion and electrochemical corrosion for both materials under different angles of impingement and to determine the extent of interaction between corrosion and mechanical-erosion processes.