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.

This study assesses the mechanical performance of cold-sprayed aluminum 6061 coatings heat treated using focused IR radiation. The heat treatment was performed in-process with the aim of improving the ductility and strength of the coatings. The properties of the heat-treated samples are compared to those achieved using traditional annealing and as measured in as-sprayed samples. It was found that the rapid IR heat treatment increased the ultimate tensile strength of the coatings by 52% and elongation at failure by 43%.

This study demonstrates a novel method for improving the corrosion resistance of cold sprayed Al6061 coatings. Large stainless steel particles were added to a commercial Al6061 powder and the mixture was deposited on Mg alloy AZ31B substrates using nitrogen gas at low working pressure and temperature. It is shown that the stainless steel particles had a shot-peening effect, thus increasing the density as well as the corrosion resistance of Al6061 coatings. SEM examination showed that no stainless steel particles were incorporated in the coating.

The mist cooling technique was developed and applied to various thermal spraying guns. For example, aluminum-magnesium coatings prepared using a gas flame thermal spraying gun with mist cooling had superior anticorrosion characteristics. Stellite coating thermally sprayed with mist cooling had higher anti-cavitation-erosion characteristics. Next, we endeavored to develop high velocity oxygen fuel guns with mist gas cooling to improve high-temperature toughness.

The residual stresses present in coatings and layer composites are influenced not only by the thermal and mechanical loads generated during manufacturing, but also by the mechanical and thermophysical properties of the coating and substrate materials. In-process measurement of transient, process-induced stresses may thus enable the manufacturing of coated parts with a residual stress state that lies within a predefined application-oriented stress regime. This paper presents a quasi-nondestructive method by which such measurements may be obtained. A small amount of material is removed from the surface of a part by laser ablation, while optical interference sensors monitor surface deformation caused by stress relaxation and heating due to absorbed laser energy. The new method is evaluated by four-point bend testing using Al5754 plates coated with Al/TiO 2 by atmospheric plasma spraying.

This study assesses the potential of an amorphous-type steel for use as a thermal barrier coating (TBC) on aluminum surfaces. A high-alloy steel powder was deposited on aluminum 6061 substrates by plasma spraying. Coating samples were examined, then thermally cycled to failure. The coatings showed good microstructural stability up to 500 °C, but their spalling resistance was inferior to that of arc-sprayed stainless steel, probably due to lower initial bond strength.

This study evaluates the influence of shot peening on the fatigue life of cold spray aluminum alloy 6082 coatings. A pneumatic blast machine with standard steel shot was used to peen both uncoated and coated substrates. Six test groups representing different treatment protocols were characterized in terms of residual stress, roughness, and rotating bending fatigue. The results show that the best fatigue performance is obtained by intense shot peening prior to cold spraying. Post-treatment shot peening, in contrast, had a detrimental effect as a large portion of the kinetic energy is absorbed in the coating, resulting in surface damage rather than further work hardening.

In order to broader thermal spraying applications and reduce constraints and time due to conventional surface preparation before thermal spraying, the PROTAL process was developed over the last decade. This process integrates laser ablation, using a Q-switched Nd-YAG laser to prepare the surface simultaneously to the coating build-up during Plasma or HVOF Spraying. The present paper aimed at evaluating the feasibility to use the Protal technology in conjunction with the Twin Wire Arc deposition (Arc spraying) onto the 7075 Aluminum based alloy and to define the optimal Protal process parameters. Coating adhesion, micro-gap at coating-substrate interface and the coating residual stresses are evaluated. The Protal parameters investigated are: the laser energy density onto the substrate and the coating layers, the number of laser passes and the time delay between the laser impact. This study results indicate that it is feasible to use the Protal technology in-situ with the Arc spray process in spite of the challenging overspray and the large plume size of the Arc process. Good adherence and absence of interface micro-gap is obtained with an appropriate range of laser energy density to ablate the substrate. The use of a low energy ablation prior each coating layers reduces coating tensile residual stresses and improves furthermore the bond strength. The elimination of the process ablation dust and overspray dust prior the coating deposition onto the plane substrate was found critical to obtain a good bond strength. This research results from collaboration between the LERMPS in France and National Research Council Canada. Abstract only; no full-text paper available.

Cold Gas Dynamic Spraying is a relatively new high rate deposition process that uses a supersonic gas flow to accelerate fine powder particles (micron size) above a critical velocity. Upon impact, the particles deform plastically and bond to the substrate to form a coating. In this study, nanocrystalline Al-Mg coatings are produced using the Cold Spray technology. In an attempt to improve the understanding and optimize the process, the effects of substrate preparation and substrates thickness on the overall quality of the coatings are investigated. Two different grit materials are used to prepare the substrates with simple grit-blasting. Results show that the use of different grit sizes leads to changes in the mass deposited on the substrate (deposition efficiency) but has no significant effect on the coating microstructure. Other trials are conducted on samples of different thickness to verify the applicability of the Cold Spray process on thin surfaces. Results show that the Cold Spray process can be used to produce coatings on thin surfaces without noticeable damage to the substrate and with the same coating quality.