This paper provides an update on the state of cold spray corrosion mitigation and repair as it applies to equipment operated by the U.S. Navy. It also presents several application scenarios in which cold-sprayed Al 6061 and NiCr-CrC can improve preventative maintenance and dimensional restoration procedures currently used on A36 steel and CuNi structures.

An internationally recognized best practice for disposing used nuclear fuels is to store them in specially designed containers in deep geological repositories. One type of spent fuel container is a carbon steel canister with a cold-sprayed copper coating. The aim of this study is to assess the impact of various factors on the ductility of this protective copper layer. The current investigation finds that there can be significant variability in ductility when feedstock powder size and chemical composition are changed while keeping spraying and heat treatment conditions constant. Test results show that the ductility of nitrogen-sprayed copper decreases with increasing hardness, but can be improved by raising annealing temperature from 300 to 600 °C. The effects of substrate geometry and process variations are discussed as well.

This paper describes the development of cold-sprayed chromium coatings that are used to increase the corrosion and wear resistance of zirconium-based nuclear fuel cladding tubes. Significant effort was necessary to deposit very thin layers of chromium on 4 m long, 10 mm diameter tubes by cold spraying. As explained in the paper, a final polishing step is used to reduce surface roughness and adjust coating thickness to the desired specifications.

This study assesses the erosive wear performance of hard-phase-reinforced coatings developed for use on hammer drills employed in mining operations. Several laser-clad coatings consisting of a nickel matrix with various tungsten carbides were evaluated along with two Fe-based alloys, FeCrBSi and FeCrNiBSi, and a WC-CoCr reference layer deposited by HVOF spraying. Erosion tests were conducted in 15° steps up to an angle of 90° and coating performance was determined based on volume loss obtained by 3D profilometry. At low angles, the more brittle materials lost significantly less volume, but at 90°, wear-resistant steel performs almost as well as a hard-phase loaded coating. Laser-clad layers with spherical fused tungsten carbides (FTC) performed better overall than coatings with regular (angular) FTC.

Cold spraying of automotive engine blocks requires a gun adaptation for inner diameter spraying with a very short nozzle. In this work, 316L coatings are sprayed with such a gun and the behavior of particles impacting aluminum and stainless steel surfaces is studied in order to understand the factors that affect coating adhesion and cohesion. Correlations between spraying parameters and coating properties were investigated via design of experiments and the effect of process parameters on deposition efficiency and coating thickness was optimized for mass production. Post-process honing was also employed as part of the study and smooth coatings with small pores were obtained.

In this paper, the principles of computational fluid dynamics are used to simulate the complex gas flows in the cylinder bore of an automotive engine during internal-diameter twin-wire arc spraying. A number of experiments are conducted as well and the results are presented and analyzed in order to optimize the properties of the coating. The combination of simulation and experiments led to the development of a process that achieves uniform layer adhesion strength over the length of the cylinder bore.