In this study, Ni-alloy 718 coatings are deposited on substrates of the same material using laser assisted cold spraying (LACS). The laser heats the substrate surface making it more ductile and expands the metallurgically bonded region. Coatings deposited at various track spacings and surface temperatures are examined to assess coating quality, level of deformation and recrystallisation, and the effect of different track spacings on surface roughness and waviness. A track spacing of 3.5 mm was found to provide the most even coverage with the laser. Surface X-ray diffraction measures residual stress for different layers at various surface temperatures while incremental hole drilling measures stress profiles for coatings of varying thickness. All coatings were found to be well bonded with low porosity.

In this study, nitrogen is employed rather than helium to cold spray MCrAlY coatings at relatively low process settings. Recycling of the non-deposited particles during the spray is also explored, and the characteristics and cold sprayability of recycled powder are compared with that of as-received feedstock powder. The resulting MCrAlY coatings from the two powders, though different thicknesses, show similar dense microstructures, low oxide inclusion, and smooth surface finish, all of which contribute to improved oxidation behavior.

High-entropy alloys are of great interest due to their unique phase structure. They are constructed with five or more principal alloying elements in equimolar or near-equimolar ratios and thus derive their performance from multiple elements rather than one. In this work, solid-state cold spraying is used for the first time to produce a FeCoNiCrMn high-entropy alloy coating. As a low-temperature process, cold spraying completely retained the high-entropy phase structure in the coating without any phase transformation. Examination shows that the grains underwent significant refinement due to dynamic recrystallization and that the coatings are much harder than the feedstock powder because of increased dislocation density and grain boundaries.

Cold spraying is a promising process for fabricating functional coatings. Because of the solid-state particle deposition, the electrical and chemical properties of the coatings are similar to those of the bulk materials. Mechanical properties, on the other hand, differ from those of bulk materials due to severe plastic deformation of the particles. Residual stress may thus be an important variable to track during cold spraying although the formation mechanism is not entirely clear. In this study, the residual stress of metallic (copper) and ceramic (titania) coatings is measured during the cold spray process. The results are presented and discussed.

In this work, a fine copper layer was deposited on an aluminum nitride substrate via cold spraying. Parametric modeling was used to develop a parameter selection map that helped guide preliminary experiments to validate the model for different substrate surfaces, nozzle geometries, gas dynamics, standoff distances, and deposition angles. Further modifications were then made to include failure prediction based on particle impact, leading to the deposition of well-adhered cold-sprayed copper on a ceramic surface.

This study assesses the feasibility of cold spraying metal onto wood for commercial applications. It was found that particle adhesion and coating build-up differ significantly from the standard case of spraying metal on metal. Phenomena such as fiber rupture and buckling, pore filling, and particle anchoring required a new approach for process development and verification. First, a microscale analysis of the unique features of wood was necessary to define the deposition surface. Next, a wide range of cold spray tests were conducted to obtain metal coatings on four species of wood. To better understand the dependency of deposition efficiency on particle state conditions, a CFD models and FEA simulations were used to investigate single and multi-particle impacts on local wood structures as observed in SEM and microtomography images. A conventional pull-off test was used to collect adhesion strength data and a numerical counterpart of the test has been developed, making it possible to compare macroscopic adhesion behavior of real and virtual interfaces.

This study focuses on the relationship between porosity and leak tightness in cold-sprayed aluminum. Aluminum coatings with 0.2-9% porosity were produced by cold spraying and evaluated via helium leak testing. Multiscale porosity was determined through SEM and TEM analyses and shows good correlation with leak test results. The mechanisms involved in the creation of porosity were investigated as well through finite element analysis of single and multi-particle impacts.

This study investigates the effect of thermal cycling on cold-spray chromium coatings deposited on steel substrates. First, equilibrium stress states are determined for different coating thicknesses. Next, the potential for crack initiation and growth is simulated based on periodic heating and cooling cycles. The corresponding crack driving forces are characterized using interface stresses and energy release rate as a function of the thermal cycles. The effects of coating thickness, embedded microcracks, and initial residual stress on the driving forces are investigated systematically to demonstrate the risk of coating fracture and delamination.