A systematic study on the relationships between the structure and abrasive wear resistance of autocatalytic nickel-phosphorus coatings (particle-free and SiC composite) with different phosphorus contents (i.e. 2.5-10.2 wt.% P) and under different thermal treatments (i.e. 300, 400 and 500 o C) has been performed. The phase structure, composition and properties of the coatings could be controlled by changing the phosphorus content of the nickel-phosphorus matrix and by performing thermal treatments. The improvement in abrasive wear behaviour of the nanocrystalline (i.e. =<6.0 wt.% P) coatings with heat treatment temperature up to 400 o C was related to (i) the formation of a metastable equilibrium phase and (ii) precipitation of Ni 3 P compound. At higher thermal treatments (500 o C), a change in the deformation mechanisms (Orowan mechanism) determined by the coarsening of Ni 3 P precipitates was associated with the decrease in abrasive wear resistance of the coatings. In addition, for the NiP-SiC coatings after annealing at 500 o C, Ni 3 Si was formed and the adhesion between the reinforcement and the matrix was enhanced.