Selection of wear resistant materials for the petrochemical industry

Abstract

Mechanical equipment used in BP operations is subjected to extremely adverse conditions, often in remote locations. Downtime due to wear and component failure can be very costly and the need to choose materials based upon an understanding of wear resistance is required. Selection is often based on the economics of component manufacture and on physical properties of materials such as hardness and toughness. It is often assumed that selecting materials on the basis of suitable physical properties will automatically lead to their possessing wear-mitigating properties but, in practice, this is not always the case. To help reduce wear of critical components, BP have developed a suite of laboratory test methods to provide basic insight into the wear performance of new materials as an aid to the material selection process. In this paper, wear results are presented from a series of pin-on-disc and slurry impingement erosion tests performed on stellites and ceramics, materials already in use in applications requiring superior wear properties. Through an understanding of wear mechanisms, simple laboratory test methods can be used to simulate the hostile environmental conditions experienced in service and enable materials to be ranked according to their resistance to abrasive, erosive and adhesive forms of wear. Consideration of wear mechanisms in pin-on-disc studies has identified factors such as transitions from mild oxidative to severe adhesive wear in metallic samples and thermally induced spalling of ceramic samples which leads to order-of-magnitude increases in wear rates as sample loading is increased. Profilometry of slurry erosion scars reflects differences in the erosion mechanism for ductile and brittle materials.