In this study, a mathematical model based on 2D heat conduction was developed to determine the temperature distribution within different substrate materials during cold gas dynamic spraying. Heat transfer between the hot gas and substrate was estimated theoretically and experimentally and the results were compared with those obtained from numerical studies. The heat transfer coefficient was found to be dependent on the distance from the stagnation point of the impinging air jet. It was also concluded that at higher air jet temperatures, the Nusselt number of the spreading air film near the stagnation point could be affected by external heat exchange with colder ambient air.

This study shows that surface preheating is required to avoid delamination of flame sprayed coating glazes. In the experiments, preheating parameters are determined from heat flux measurements and potential substrate degradation is characterized and controlled by optimizing spray parameters. Coating adhesion is determined by pull-out tests and remains constant even after freeze-thaw cycling. Although gas tightness was not characterized, aging tests show that no water percolates through pore networks in the coatings.

Multilayer ceramic chip capacitors (MLCCs) are produced in large numbers for use in automobiles, cell phones, flat panel displays, and other products. Like many circuit components, they are being required in more compact sizes, larger capacities, and reduced costs year by year. MLCCs are kiln-fired on stacked carriers made from Al 2 O 3 -SiO 2 covered with a Y 2 O 3 -stabilized ZrO 2 topcoat and an Al 2 O 3 basecoat. This paper presents the rationale behind the selection of the coating materials and evaluates processes by which they can be applied. It compares the microstructure and properties of sintered, atmospheric plasma sprayed (APS), and water stabilized plasma sprayed (WSP) yttria-stabilized zirconia and discusses the advantages and disadvantages of each process.