Tungsten carbide coatings are often applied to improve surface properties such as wear, high temperature degradation, and corrosion resistance. Zirconia coatings have also been used extensively in various industries due to their excellent tribological and insulation properties combined with high stiffness. It is speculated that adding zirconia to tungsten carbide may result in a coating with combination of excellent thermal and mechanical properties of constituents. In the current study, a powder mixture of 50 wt. % WC-Ni and 50 wt. % ZrO 2 -Y 2 O 3 deposited on a low carbon steel substrate using atmospheric plasma spray technique. The microstructural evolution of deposited sample was investigated. Splat boundaries, micro cracks, pore morphology conversion, and grain growth mechanism were elucidated comprehensively. Results indicated a good adhesion between two different major components. No porosity formed due to mismatch between zirconia and tungsten carbide. This study pays special attention to the dependency of the microstructural characteristics to the phase distribution within the coating.

In this study, nickel-matrix composites reinforced with nickel-aluminide particles are produced by cold spraying and powder metallurgy techniques. A powder mixture of 80 vol% Ni and 20 vol% Ni3Al is used in both processes. Optical microscopy, SEM, and EDX analysis are used to evaluate the microstructural uniformity of the as-fabricated composites, while hardness and Young’s modulus are determined by microindentation tests. Microhardness tests are also conducted after each step of the P/M process in order to evaluate corresponding changes in hardness. The findings are presented and explained.

Recently, an advanced technique was developed to fabricate sandwich structures for high temperature applications by depositing alloy 625 skins on Ni alloy foam core by thermal spraying. This study tries to utilize an analytical model to estimate the mechanical performance of these structures based on the mechanical properties of the constituents. The mechanical behavior of the Ni alloy foam is assessed via compression testing, while tensile tests are used in the case of the alloy coating. The flexural rigidity of the sandwich structure is calculated using analytical models and experimentally obtained elastic moduli of the alloy 625 coating and Ni alloy foam. The model is also used to calculate the flexural rigidity of sandwich samples with different skin thicknesses to check the accuracy of the model and to understand the effect of skin thickness on the predicted mechanical performance of sandwich structures. The effect of heat treatment on the mechanical behavior of sandwich structures is investigated as well.

The structure of thermally sprayed deposit consists of individual lamellae formed from melted and re-solidified particles, along with unmelted and partially melted particles, pores, microcracks, and splat boundaries. The elastic modulus of a vacuum plasma sprayed Ti-6Al-4V alloy parallel to the splat plane determined by standard uniaxial tensile testing was found to be approximately 30% lower than that of conventionally processed materials with the same level of porosity. The relationship between the elastic modulus and the microstructure was studied using an in-situ tensile testing stage in an optical microscope combined with analytical and finite element models. An idealized microstructure was used for the analytical model, which yielded an estimate of the modulus higher than that measured. The finite-element program OOF was also used to compute the elastic modulus based on micrographs of polished and etched surfaces and predicted a reduction of about 37% in the modulus.