The abrasive wear properties of nanocrystalline nickel-phosphorus alloy coatings with phosphorus content up to 5.9 wt% produced by electrodeposition were studied using Taber wear testing. For materials showing the highest wear resistance in the as-plated state (Ni-1.8 wt% P), the effect of annealing on the hardness and wear resistance was further investigated in a series of isochronal and isothermal heat treatments. The effects of annealing temperature (200similar to600 degreesC) and time (up to 2 hours) on the microstructural evolution (i.e. grain growth, formation of Ni3P precipitates, change in crystallographic texture) are discussed. It is shown that a heat treatment of 1 hour at 370 degreesC produced a microstructure with the highest hardness and wear resistance for the time-temperature ranges covered in this study.