Tribology of Selected Hard Coatings for Oil and Gas Applications Up to 450 °C

Abstract

Three different surface treatments, which are of interest to the oil and gas industry, and are commonly used for tribological applications at elevated temperatures, namely chromium carbide (CrC) coating, Ni–P coating, and boronized nickel alloy were investigated. In addition to different structural compositions, these surface treatments possess different surface topographies, which is of practical importance. Pin-on-disk experiments were conducted to measure their friction and wear performance against tungsten carbide. Experiments were carried out at room temperature and 450 °C using a specialized tribometer. Nanomechanical properties of the coatings were obtained at room and elevated temperatures. To investigate the physical and chemical changes that occurred during tribo-testing, scanning electron microscopy of the coatings’ cross section, wear tracks, and wear debris were obtained. Energy-Dispersive X-ray Spectroscopy analysis revealed the changes in elemental composition of the coatings wear track after the experiments, which could affect their tribological performance. It was found that the intensity and composition of the generated oxides, changes in the mechanical properties of the surface materials with temperature, and the surface topographical characteristics affected the tribo-mechanism. Among the tested samples, boronized nickel alloy surface outperformed the coatings with lower friction coefficient and lower wear rate, especially at elevated temperature.