The role of microstructural characteristics in the cavitation erosion behaviour of laser melted and laser processed Nickel-Aluminium Bronze

In this study two types of laser surface treatment, laser surface melting and laser processing, were used to treat the surface of as cast Nickel-Aluminium Bronze. The two treatments were then subjected to cavitation erosion testing and were compared against as-cast Nickel-Aluminium Bronze. While the cavitation performance of the two types of laser surface treatment was equivalent, the morphology of the eroded surfaces was different. Several materials characterisation techniques including neutron diffraction for residual stress measurements and SEM were used to explain why the two eroded surfaces were different. It was found that the tensile residual stresses in the laser melted sample weakened the sample, which negated its superior strength when compared with the laser processed sample. It was also observed that the erosion and pitting in the laser melted sample were deeper and they were attributed to the tensile residual stresses accelerating the attack at grain boundaries.