As a candidate material against plasma etching, yttrium oxide has been coated onto etching chamber by plasma spray technique. However, the plasma spray technique introduces undesirable coating properties such as porous structure and deleterious thermal effects. To reduce the disadvantage of thermal impact, cold spray was used as an alternative technology to deposit thick and dense yttrium oxide coatings. Primary nanoscale Y 2 O 3 were used as the original powder, for the ceramic materials are intrinsic brittle and are difficult to be deposited by cold spray. The nano-powder were first agglomerated by hydrothermal treatment with addition of inorganic salt to acquire suitable powder for cold spray, and then deposited on aluminum alloy 6061 substrates by cold spray process with compressed air as propellant gas. About 200μm yttrium oxide coatings were formed on the substrate alloy. Different processing parameters were employed to optimize microstructure and properties of the coating.

In this paper, we reported our investigation on preparing inorganic phosphate ceramic coatings on the surface of γ-TiAl based alloy by air spray. The high temperature performance of the coatings was tested by thermal shock test, cyclic oxidation and isothermal oxidation at 950 °C. The results showed that the coatings exhibited significant improvement on high temperature anti-oxidation performance of the base alloy. No obvious cracks or spalling of the coatings occurred after oxidation experiment under isothermal oxidation condition at 950 °C for 1000 h. The characterization was carried out to analyze the microstructure of the coatings before and after oxidation test.

This paper presents a study on Cu-Ag-Zn abradable seal coatings prepared by cold spraying. The micro-morphologies of the coatings were analyzed using scanning electron microscopy and electron dispersion scanning. The hardness of the coatings was analyzed. Thermal shock tests were conducted to evaluate the combination strength between the coating and the substrate. The friction and wear properties of the coatings were also tested. Two methods, annealing the coatings in vacuum and heating the feed powders in cold spraying, were tried to improve the combination strength and quality of the coating. The results showed that Cu-Ag-Zn coatings made by cold spraying with powder heating exhibited better combination strength and anti-friction properties compared to coatings annealed in vacuum and the original samples. The paper also proposed a combination mechanism for the Cu-Ag-Zn coatings.

Cold spray is a promising potential material deposition process of which the main advantage is that the material to be sprayed is not heated to high temperatures. But one problem encountered is that the coatings for some powders are not well bonded to the substrate. The mechanisms of bonding of cold-sprayed coating to substrates are not at present clearly understood. This work considers the deposition of aluminum bronze by cold spray process onto stainless steel. The micro diffusion along the interface between the substrate and coating as well as the beta-phase depletion of the cold-sprayed coating is observed. Results obtained are important not only for understanding the interaction of the particles with the substrate but also for optimizing the spray parameters for the cold spray process.