Annealing effects on plasma-sprayed Ni: An XRPD study

The variation of the size of coherently-diffracting domains and strain due to annealing at moderate temperature (500 °C) has been estimated for plasma-sprayed Ni using X-ray Powder Diffraction (XRPD) and line broadening analysis in conjunction with classical and modified Williamson–Hall methods. It was found that annealing provokes a narrowing of Ni diffraction peaks which was basically associated to a decrease in dislocations present in the as-sprayed material. The evolution of the microstructure with temperature of plasma-sprayed Ni was studied by in situ X-ray Powder Diffraction (XRPD). It was found that the breadth of the Ni profiles continuously decreased with heating up to 500 °C, mainly due to healing of dislocations. These results were used to explain the irreversible decrease in electrical resistance of plasma-sprayed Ni resistors after annealing which was previously observed in our laboratory.