| Abstract: |
The cavitation erosion result mass loss. Surface welding is the most comum technique used to recover the geometrical profile of the blades. However it is known that tensile residual stress can develop. The search for manufacture process that could reduce or eliminate the residual stress level will contribute for a longer service life. It is aimed in this study to evaluate the potencial of ASP thermal spray to recover surfaces that were exposed to cavitation erosion. The influence of processing parameters on the cavitation resistance and mechanisms was evaluated for two steels, AIS309L and a Co stainless steel known as Cavitec. Coatings were analyzed by optical and eletronic microscopy, micro and nanohardness and cavitation tests (ASTMG32-92) regarding the effetct of ?stand-off? distance, current intensity and air pressure. The results showed that lamellae morphology, oxide volume fraction and cavitation resistance were modified by the ASP parameters. The increase in the pressure modified the oxide fraction from 15 to 36% in AISI309L and 13 to 23% for Cavitec. The reduction on the stand-off distance promoted an oxide reduction in Cavitec to 12% for all air pressure conditions, the stand-off did not modified the oxide fraction content on the AISI309L. Mass loss varied from 3,5 to 4,7mg/h for AISI309L, and varied from 3,2 to 5,1mg/h for Cavitec, the best performance was associate with minimum oxide fraction and intermediate pressures. The mass loss occurred by interlamellae oxide removal, followed by detachment of the lamellae, it was localized in the areas with high oxide fraction.
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