| 摘要 |
Thermal sprayed ceramic coatings are successfully employed to enhance the load carrying capacity and the tribological performance of the base material in order to extend the in-service life of equipment, including metal-seated ball valves (MSBV's) in Hydrometallurgy service. Ceramic coatings are vital to protect machines in the harsh abrasive conditions encountered in corrosive processes such as Pressure Oxidation (POx) and High Pressure Acid Leach (HPAL). Velan, a leading designer and manufacturer of industrial valves, has 20 years of experience in the engineering of severe service MSBV's for critical isolation applications around the autoclave. The National Research Council of Canada (NRC) in Boucherville and Polytechnique Montreal have world recognized know-how on coating engineering and characterization, in particular for wear. A detailed characterization project was undertaken by Velan in collaboration with the NRC and Polytechnique Montreal to perform mechanical and tribological resistance evaluation of the most promising ceramic coatings potentially suitable for this service, including a novel blend of n-Ti02-Cr2O3. Hardness and shear strength were evaluated using micro-hardness indentation testers and universal tensile testing equipment. Wear resistance of the coatings under different conditions such as sliding wear, abrasion and galling were measured by standard pin-on-disc tests, abrasion tests and custom-design galling tests. It was found that TiO2-Cr2O3 offers superior tribological performances compared to n-TiO2, mainly due to the presence of Cr2O3. Optimized balance between the hard and brittle Cr2O3 phases and the soft and ductile TiO2 phases yields to higher abrasion, sliding and galling resistance. In parallel, the novel mix of n-TiO, and Cr2O3 is considered as a promising evolution of the current TiO2-Cr2O3 blend. |
