Young's modulus, hardness and scratch adhesion of Ni-P-W multilayered alloy coatings produced by pulse plating

The effect of layering on Young's modulus, hardness and deformation behaviour of Ni-P-W multilayered alloy coatings in a scratch adhesion test was studied. The coatings were deposited on copper substrates by electro-deposition and the wavelengths studied were 8-4000 nm. The Young's moduli of the amorphous multilayered Ni-P-W coatings, measured by an acoustic-wave resonance method, are higher than the Young's modulus of crystalline nickel. Their hardness was found to increase with decreasing wavelength of the coatings, the increase being more pronounced for wavelengths below 120 nm. The cohesive load of the multilayered coatings ranges from 5 to 16 N, while the critical load range for coating detachment in scratch adhesion tests was found to be 50-75 N. The values of adhesive and cohesive loads seem to be independent from the wave-length of the Ni-P-W coatings. The failure modes observed in the scratch tracks of the Ni-P-W multilayered coatings are common in every coating in the scratch tests under increasing load, and they are a result of substrate deformation and coating brittleness. (C) 2001 Elsevier Science B.V All rights reserved.