Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
COMPARRISON OF SLURRY JET EROSION BEHAVIOUR OF THERMAL SPRAY COATINGS WITH DIFFERENT LEVELS OF HARDNESS
Submission Author:
André Chicoski , PR
Co-Authors:
André Chicoski, Ramón Sigifredo Cortés Paredes, Gustavo Bavaresco Sucharski, Anderson Geraldo Marenda Pukasiewicz
Presenter: André Chicoski
doi://10.26678/ABCM.COBEM2021.COB2021-2042
Abstract
Currently in Brazil, more than 60 % of electric energy comes from hydro generation, whose installed power exceeds 109 GW. In hydroelectric generation, some mechanical components are often exposed to wear phenomena, usually cavitation and/or solid particle erosion. Such phenomena are capable of generating significant damages to the components exposed to the water flow, mainly in the hydraulic turbines, bringing as consequence, significative losses due to the maintenance costs and the loss of production. The use of coatings is an alternative to reduce the wear and, in this scenario, thermal spray technology appears as a relevant solution due to its versatility and ability to apply protective layers with different mechanical, physical or chemical properties with minimum or no impact to the component substrate. Regarding to solid particle erosion, it is usual the application of hard coatings like martensitic steels or chromium / tungsten carbides. In this work, two wear resistant commercial alloys, with different levels of hardness, were applied on carbon steel substrate by Arc Spray Process (ASP) and subjected to slurry jet tests with constant parameters – angle of incidence (90 °), jet speed (25,5 m/s), type and rate of erodent (sand 300 µm and 1790 g/min). The influence of surface finishing – using single step sanding or full polishing – on the wear rates was also verified. The results indicated that the coating behaviour tends to be similar to that expected for bulk materials, in which, for incidence angle of 90 °, the wear rate is bigger for harder alloys. Scanning Electron Microscope (SEM) analysis of the eroded surfaces showed different wear mechanisms according to the hardness of the coating. The softer material was affected by micro-ploughing and micro-cutting effects, while, on the harder coating, micro-cracking and fragile fracture were predominant. The surface finishing – sanding and polishing – reduced the initial wear rates for both alloys, however, it did not compensate the mass loss caused by the finishing processes themselves.
Keywords
Erosion, thermal spray, Slurry Jet, coating
