Thermal stability and mechanical properties of Ni–W–P electroless deposits

The ternary Ni–W–P alloy coatings were deposited by electroless plating on 420 stainless steel to evaluate the thermal property and related mechanical characteristics of the coating assemblies. The thermal stability of electroless Ni–W–P deposits, analyzed by differential scanning calorimetry (DSC), could be enhanced by the co-deposition of tungsten as compared to binary electroless Ni–P films. The phase and composition of Ni–W–P and Ni–P were evaluated by X-ray diffraction technique and electron probe microanalysis, respectively. The co-deposition of tungsten enabled the deposits to exhibit an amorphous structure with lower phosphorus content. Adhesion strength of the deposits on the substrates were assessed by a scratch test. The introduction of the tungsten in the Ni–P coating effectively reduced the linear crack length and delayed the cracking formation. Surface hardness of binary alloy coating could be modified with the introduction of the tungsten element.