INFLUENCE OF TIG RE-MELTING AND RE (La_2O_3) ADDITION ON MICROSTRUCTURE, HARDNESS AND WEAR OF Ni-WC COMPOSITE COATING

摘要

This paper describes the effect of lanthanum oxide (La_2O_3) and remelting on microstructure, hardness and abrasive wear behavior of Ni-WC composite powder flame sprayed coatings. It was found that La_2O_3modification and remelting of flame sprayed Ni-base composite coating refined the microstructure and increased microhardness and resistance to abrasive wear. La_2O_3 modification and remelting of the coating increased hardness by 1.2 to 1.3 folds. Abrasive wear behavior of unmodified and La_2O_3 modified coating in as sprayed and re-melted conditions were studied for different normal loads (5, 10, 15 and 20N) and abrasive mediums of 120 and 600 grit sizes. La_2O_3 modified composite coating in re-melted condition showed minimum wear rate irrespective of normal load and abrasive medium. Abrasive wear study results were supported by SEM analysis of worn out surfaces.