DEGRADATION MECHANISMS OF A COBALT-BASE ALLOY AND STAINLESS STEEL UNS S17400 USED FOR DRILLING TOOLS BY THE OIL INDUSTRY

摘要

Two materials which are candidates in the construction of drill bits have been studiedrnin severe liquid-solid impingement conditions. Analysis of the total weight loss wasrncarried out on Stellite X40 (Co-base) and UNS S17400 (stainless steel) materials atrn30o, 60o and 90o angles of impingement under erosion-corrosion conditions at thernfree corrosion potentials and with applied cathodic protection.rnA preliminary analysis of the corrosion behaviour of the materials in static conditionsrnwas the starting point for the electrochemistry analysis. A more extensive corrosionrnanalysis under erosion-corrosion conditions was carried out through DCrnpotentiodynamic tests while varying angle of impingement to detect the effect on theirrncorrosion behaviour. The results were used to identify the contribution ofrnmechanical erosion and electrochemical corrosion for both materials under differentrnangles of impingement and to determine the extent of interaction between corrosionrnand mechanical erosion processes.