Surface morphology and structure of Ni–P, Ni–P–ZrO2, Ni–W–P, Ni–W–P–ZrO2 coatings deposited by electroless method

Electroless binary Ni–P and ternary Ni–W–P alloy coatings and electroless composite (Ni–P–ZrO2 and Ni–P–W–ZrO2) nickel coatings were deposited. Baths with aminoacetic acid as the complexing agent were used. ICP measurements showed that the P content depending on the type of coating is in a range of 4.7–6.3 wt.% (at pH = 6, t = 75 °C). The tungsten content is around 1–2 wt.%. SEM examinations show that the electroless Ni–P coating has the most fine-grained structure. Grains in the form of microspheroids 20 μm in size are characteristic of the Ni–P–ZrO2 coating. X-ray diffraction patterns show that for all the obtained coatings peak Ni(111) located around 2θ = 44° is the most intensive. After the coatings are heat treated at 400 °C for 1 h the peak becomes even sharper. The heat treatment results in a nearly double increase in crystallite size. The quaternary coatingsʹ abrasion resistance is determined by the second-phase (ZrO2) particles present in them.