Analysis of the wear damage on offshore gas turbine blades

A study of the wear damage of a blade of the seventh-stage of the compressor of a gas turbine was carried out. The manufacturer recommends routine maintenance (30,000 h) to reduce the chances for the shutdown of the gas turbine. In this study, the C40 turbine was analyzed in the field at 24,000 h (shutdown) and out of service after 30,000 h. The turbine was operating in the city of Campeche, Mexico, in a very aggressive environment, where the entry of solid particles is unavoidable. The gas turbine combines high performance operation with rugged industrial construction. This design provides high efficiency, low maintenance and a long service life. For power generation, the components that are in direct contact with the air at different stages of operation are the compressor blades which are exposed to severe wear damage for the impact of particles, environmental contaminants such as salts, sands and sulphur. Due to this fact, the wear damage on the turbine blades was analysed. The work was developed in two steps. In the first one, an analysis of boroscope images of the surfaces of the blades was carried out in the site, and out of service the study with destructive and non-destructive tests, using tribological characterization were conducted to obtain the chemical composition of the turbine blades, which were in operation, by using energy dispersive X-ray analysis (EDS). Hardness tests were also conducted, using the material that was employed to manufacture the blades. Additionally, optical microscopy and scanning electron microscopy (SEM) were used to identify the wear mechanisms on the surfaces. This allowed obtaining a more complete failure analysis. The wear modes were severe pitting action, large craters similar to those observed in solid particle erosion when the samples are impacted at normal incidence, corrosion and a few irregular scratches similar to ploughing action in abrasive wear.