Crystallization behaviors and microhardness of sputtered Ni-P, Ni-P-Cr and Ni-P-W deposits on tool steel

The Ni-P-based coatings, including binary Ni-P, ternary Ni-P-Cr and Ni-P-W, were fabricated by the RF magnetron sputtering technique with dual target of electroless Ni-P alloy and a third metal element. To evaluate the influence of the doping element in Ni-P deposit, differential scanning calorimeter (DSC) analysis was employed to characterize the temperature of phase transformation. The phase transition during thermal evolution under heat-treatment was analyzed by X-ray diffractometry (XRD). Crystallization behavior in binary and ternary Ni-P-based coatings was quite distinct due to the addition of Cr and W. Microhardness tests indicated that the sputtered Ni-P-Cr and Ni-P-W coatings exhibited superior hardness and excellent thermal stability than the Ni-P coating. In addition, chromium exhibited compatible thermal characteristics with the tungsten for the ternary Ni-P-based system. The strengthening mechanism in the sputtered Ni-P-Cr and Ni-P-W deposits is also discussed. (C) 2003 Elsevier B.V. All rights reserved.