Narrow Results

Amorphous Ni–W–P coatings were prepared by electroless plating and annealed at 250${}^{\circ }$C for different times to obtain different microstructures. The local atomic structure of these amorphous coatings was analyzed by calculating the atomic pair distribution function from the XRD patterns. The type of crystals in coatings was obtained from the TEM image and corresponding selected area diffraction (SAED) pattern. The proportion of microscopic particles in the matrix was roughly estimated from the first DSC exothermic peak area. Corrosion resistance in 0.5-M sulfuric acid solution was investigated via electrochemical techniques. Experimental results showed that all annealed coatings still held amorphous structure, albeit the microstructure had been changed. The correlation radius and the atomic number of clusters had increased, especially when the annealed time extended to 12 h and 20 h. The number of microscopic particles in the amorphous matrix also increased with rise in heat treatment time. The type of crystals in these amorphous matrices increased from Ni/Ni (W) to Ni/Ni (W), Ni₁₂P₅ and Ni₅P₄. The decreasing corrosion resistance was in agreement with the increasing number of microscopic particles and higher-order clusters in annealed Ni–W–P coatings. These microscopic particles could form micro-galvanic cells in corrosion solution. The higher-order clusters increased the composition difference in the amorphous matrix, and this also promoted to form micro-galvanic cells in solution.

The tensile behavior of amorphous layer coated SiC nanowires was investigated using molecular dynamics with Tersoff potential at room temperature. Simulation results show that the amorphous layer coating leads to the decrease of the critical stress and Young's modulus, but does not affect the fracture mode of nanowires with large diameter and thin coating layer. The decrease of critical stress and Young's modulus can be attributed to the weakening of the Si–C bonds in the amorphous coating layers.

A thin strip of a Zr-based alloy with a composition of Zr₆₀Cu₂₅Fe₅Al₁₀ (in atom percent) was used as a raw material, and the composite coatings containing Zr-based amorphous phase and crystallites on Ti substrate were fabricated by a one-step laser cladding method without protection. The microstructure, phase constitution, microhardness and wear properties of the coatings were investigated. The results indicate that the microstructure of the coatings is strongly dependent on the laser scanning speed under the conditions of the laser power of 1300 W and laser beam diameter of 6 mm, and the composite coating mainly containing amorphous phase with a small amount of the crystallites can be obtained at the laser scanning speed of 10 mm/s. The composite coating exhibits much higher microhardness than the pure Ti substrate, and thus it behaves superior wear resistance in comparison with the substrate.