Residual stresses and mechanical behavior of nickel-boron coatings

Two nickel-based coatings obtained from electroless plating baths are studied. The first one is studied as-deposited whereas the second one was subjected to a heat-treatment. Hardness and Young's modulus of coatings have been investigated by means of indentation tests. Results show that mechanical properties are homogenous in the whole thickness of the coating. On the other hand, the heat treatment leads on a significantly increase of hardness and modulus. Residual stresses in the coatings are studied by the incremental ring core method. Values of residual stresses are small, scattered and do not seem to be heat-treatment dependent. Without any modifications of residual stresses before and after heat treatment, mechanical properties evolutions were attributed to the microstructural modification of the coating and to the precipitation of hard phases