SiC-reinforced Al-12Si alloy coatings were produced using the Cold Gas Dynamic Spraying deposition process. Feedstock powder mixtures containing 20% and 30% vol. of particulate SiC were used. The composite coatings’ bond strengths and microstructures were evaluated, as well as the porosity and the SiC content. It was found that approximately 45% of the SiC particulate blended with the aluminum alloy was embedded in the coatings. The SiC was homogeneously distributed inside the Al-12Si matrix. Particle velocity measurements revealed that the addition of up to 30% vol. of SiC did not change the Al-12Si particle velocities.

Gas atomized feedstock particles of an Al-13Co-26Ce alloy system were sprayed using the Cold Spray deposition technique. The microstructures of the coatings produced are examined and the mechanical characteristics, in particular the bending fatigue and the bond strength, of the Al-Co-Ce coatings are reported. The results show that the Al-Co-Ce coating improved the fatigue behavior of AA 2024-T3 specimens when compared to uncoated and Al clad specimens. During the bond strength tests, the bonding agent failed and no delamination of the coating from the substrate occurred. The microstructural features of the feedstock powder were also found in the coatings. The coatings contained amorphous and crystalline phase contents similar to the ones found in the feedstock powder. It is suggested that the increase in the fatigue properties can be attributed to the residual compressive stresses induced in the coatings and to the high adhesion strength of the coatings to the substrates.

Due to their mechanical properties, WC-based cermet coatings are extensively used in industrial wear-resistant applications. These coatings are usually prepared using thermal spray processes. However, due to the nature/environment of the spraying processes, the feedstock powder structure and properties suffer from severe decomposition, which subsequently degrade the performance of the coatings produced. The cold spray process appears to be a promising process alternative to preserve the properties of the feedstock powder during the coating preparation. Although, the later technique can eliminate or minimize the degradation of the material, the deposition of cermet is a complex process. In this study, nanocrystalline WC-15Co and conventional WC- 10Co4Cr coatings were deposited using both the continuous and the pulsed cold spray processes. Microstructures of the feedstock powders and the coated layers were investigated by OM, SEM and XRD. The results revealed the possibility of depositing cermet coatings onto aluminum substrates by both processes without any degradation of the phase composition of the feedstock powder. However, the continuous process experienced difficulty in depositing and building up dense coatings without major defects. Meanwhile, the new pulsed process revealed the capacity of depositing thick cermet (conventional and nanocrystalline) coatings with low porosity as long as the feedstock powder was preheated above 573 K.

This paper describes recent effort to synthesize Fe-based amorphous alloys coatings using Cold Gas Dynamic Spraying. Characterization of the gas atomized Fe-based (Fe-Cr-Mo-WC-Mn-Si-Zr-B) powder shows that fully amorphous powder is found when particle diameter is below 20 µm. The coatings produced were composed of the same microstructure as the one observed in the feedstock powder. The overall deformation suggests the occurrence of a localized deformation process at the particle/particle boundary and possible adiabatic deformation softening inside the powder particles during splat formation. The influence of the substrate material on the coating deposition process was also investigated. The synthesis of fully amorphous, porous free coatings using Cold Spray was demonstrated in this work.

Aluminum alloy powders of different compositions and phases, Al/B 4 C, Al-Co-Ce, and Al 5083, were sprayed using the Cold Spray deposition process. The resulting coatings and the effects of several process parameters were evaluated using scanning electron microscopy and bond strength tests. The results show that the bond strengths depend on the powder composition but do not vary significantly with the powder feed rate. Adhesion strength values were obtained for Al/B 4 C and Al 5083 coatings. The Al-Co-Ce coatings failed at the coating-adhesive interface, indicating a superior adhesion strength than what was achieved in the bond strength tests.

Nickel based alloys used in coating applications have been the focus of many studies, particularly in the aerospace industry. Their inherent corrosion and oxidation resistant properties have made them especially attractive for use as the metallic bond coat found in thermal barrier coating systems. Cold Spray is an emerging coating technology in which fine powder particles are accelerated in a supersonic flow and then deposited onto a substrate by means of plastic deformation. In this study, conventional CoNiCrAlY coatings and nanocrystalline nickel coatings are produced using the Cold Spray deposition technique. The coating quality is evaluated using scanning electron microscopy as well as porosity and microhardness measurements.

The cold spray process is a relatively new coating process by which protective coatings have been successfully applied. In this process, fine powder particles are accelerated in a supersonic gas jet towards a substrate. Experimental investigations show that successful bonding of the particles to the substrate is achieved only above a critical particle velocity at which point the particles possess sufficient kinetic energy to plastically deform upon impact. Consequently, one of the most important parameters in the cold spray process is the particle velocity prior to impact. In the present investigation, the Particle Image Velocimetry (PIV) technique have been implemented to a cold spray setup. The objective was to quantify the effects of the powder feed rate on the particle velocity. Fine metal particles were cold sprayed and in-flight particle velocities were measured using the PIV technique. This paper will discuss the implementation of the systems and present results illustrating the effects of powder feed rate on the particle in-flight velocity. 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.