WATERJET ROUGHENED SURFACE-ANALYSIS AND BOND STRENGTH

Surface features of superalloys roughened by a pure high-pressure wate rjet in preparation for thermal spraying have been investigated using interferometric profilometry. Waterjet roughening was performed on Inc onel 718 and Mar-M 509, and the surface morphology resulting from this process was compared to conventional grit blasting. Results confirm e arlier reports showing that waterjet roughening yields a unique surfac e structure having some advantages over grit blast roughening. The sur face structure of waterjet roughened superalloys is shown to have a hi gh degree of microroughness and a high negative skewness of the surfac e height distribution. Tensile bond strength of an MCrAlY coating is s hown to be enhanced by waterjet roughening of the superalloy substrate . Bond testing of the plasma sprayed MCrAlY on waterjet surfaces showe d consistent high strength bonding regardless of coating thickness or superalloy type.