EFFECT OF ELECTROLESS Ni-Co-P AND Co-P COATINGS ON CAVITATION EROSION RESISTANCE

In the present work, electroless Ni-Co-P and Co-P coatings were produced on AISI 1045 steel with and without post-heat treatment. The properties of electroless coatings were characterized using an optical microscope, and microhardness tester. The cavitation erosion resistance of coatings was evaluated using a vibratory cavitation test. The test was carried out both in tap water and 3 wt.% NaCl solution, respectively. The electroless deposition characterized with low thickness films and it was higher for Ni-Co-P than for Co-P. The morphology of Ni-P and Co-P deposits were also dissimilar. Maximum hardness of heat treated samples was found to depend on the solution composition and occurs at temperature 400 degrees C. The highest erosion resistance was observed in coatings after heat treatment at temperature of 650 degrees C, when measured in both tap water and 3 wt. % NaCl solution. However, the Co-P coatings specimens could not resist cavitation erosion in 3 wt.% NaCl solution. The results showed also that the cavitation erosion resistance is independent on surface hardness.