Tribological evaluation of ZrO2 and YSZ nanoparticle reinforced electroless Ni–B coatings

This paper investigates the sliding friction and erosion resistance of untreated and heat-treated electroless Ni–B coatings, reinforced with ZrO2 and (3 mol%) YSZ nanoparticles. A ball-on-flat system was used for the sliding friction wear test, and an air jet carries solid particles for the erosion wear test. The wear scars were studied with a 3D profilometer. Further, a scanning electron microscope (SEM) for morphological and energy-dispersive spectroscopy (EDS) was used to examine the chemical properties of the worn surfaces. These scars correlate with properties of hardness, Young's modulus, and fracture toughness has been studied with microhardness and nanoindentation tests. X-ray diffraction (XRD) analyzed the coating phase structure and synthesis. The wear tests revealed that Ni–B–ZrO2 and Ni–B-YSZ coatings had lower friction coefficients at heat-treated conditions (with an average value of μ = 0.3) than Ni–B, HT, which had a 14 % higher coefficient. Consequently, the Ni–B-YSZ demonstrates the lowest specific wear rates (2.4 x10−6 mm3/N-m) and erosion resistance which is more promising for use in indented gun barrel applications.