What Really Wears Your Casing When New Hardmetals Are Used?

Abstract

ABSTRACT Tool joint hardfacing was introduced nearly fifty years ago. The primary purpose was to prolong tool joint life by reducing outside diameter wear. Tool joint life was increased up to three times.1 The hardfacing adequately protected the tool joint but often times resulted in severe casing wear by abrasion. The potential for casing damage resulted in the development of several improved types of hardfacing. Most prevalent are the smooth tungsten carbide type and iron base hardmetals alloyed with chromium. Test results by various manufacturers, users, and independent consultants indicate these new types of hardfacing are less abrasive than the tool joint steel. The primary type of wear for these hardfacing materials is adhesive. This change of wear mechanism from primarily abrasive to adhesive is a major reason why these hardfacing materials reduce casing wear. The surface finish is also a major contributor, since a smooth uniform finish reduces contact stress2. Full sized casing wear tests were performed to evaluate not only the effect of the hardfacing, but the relationship between hardfacing and available tool joint tong space. Hardfacing on the tool joint outside diameter is normally three inches (76.2mm) while the remaining tong space of the tool joint pair is fourteen to eighteen inches (355.6 to 457.2mm). Most of the current available hardfacing materials were evaluated (fine particle, coarse particle, smooth tungsten carbide, machined smooth tungsten carbide, and three iron base hardmetals). Test results indicate that when these new improved hardfacing materials are used casing wear is dramatically reduced and is significantly influenced by the steel portion of the tool joint tong space that is not hardfaced. The casing is in contact with the tool joint steel four to six times longer than the hardfacing. Since the major type of casing wear is adhesive wear for both the tool joint steel and the hardfacing material, selection of hardfacing material may be based on other criteria such as wear resistance, surface finish, ability to re-hardface, availability, price, and hole conditions.