Structure and Microhardness of Ni-P Coatings Subjected to the Low Temperature Annealing

The structure and microhardness of electrodeposited Ni-P coatings subjected to low temperature annealing at 520 K have been investigated. It is shown that the low-temperature annealing of crystalline Ni-P coatings is accompanied by a significant increase in the lattice parameter of the solid solution of phosphorus in nickel as well as the increase in microhardness of the coatings. It is concluded that the increase of microhardness and lattice parameter of Ni-P solid solution during annealing occurs due to the transition of the phosphorus atoms from the substitution positions to the interstitial positions processed by the dissociative Frank and Turnbull mechanism.