Fabrication and characterization of the Ni–P–Al–W multicomponent coatings

Nickel–phosphorus–aluminum–tungsten (Ni–P–Al–W) multicomponent coating was fabricated by multi-gun sputtering technique with novel composite target design. Through X-ray phase identification, the coatings exhibited an amorphous/nanocrystalline feature in the as-deposited state, while the W and Ni crystallites and NiP precipitates were found for the heat treated Ni–P–Al–W coatings. The transforming of coating surface from smooth to wavy contour represented the phase evolution phenomenon by the crystallization and precipitation in the Ni–P–Al–W coating. The introduction of the alloying components of Al and W into Ni–P to form the multicomponent coatings gave rise to the increase in thermal stability and surface hardness of the Ni–P-based coatings. A peak hardness of 15.5 GPa was evaluated for the Ni–P–Al–W coating under 500 °C annealing. The nanocrystallites of Ni and W and the precipitation of NiP compounds were the strengthening mechanisms for the Ni–P–Al–W coatings. In addition, the incorporated Al in the coating dissolved in Ni and W crystallites to enhance the surface hardness through solid solution effect.