Investigation of Al-Al2O3 Cold Spray Coating Formation and Properties (original) (raw)
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Cold Spray Aluminum–Alumina Cermet Coatings: Effect of Alumina Content
Journal of Thermal Spray Technology
Deposition behavior and deposition efficiency were investigated for several aluminum-alumina mixture compositions sprayed by cold spray. An increase in deposition efficiency was observed. Three theories postulated in the literature, explaining this increase in deposition efficiency, were investigated and assessed. Through finite element analysis, the interaction between a ceramic particle peening an impacting aluminum particle was found to be a possible mechanism to increase the deposition efficiency of the aluminum particle, but a probability analysis demonstrated that this peening event is too unlikely to contribute to the increment in deposition efficiency observed. The presence of asperities at the substrate and deposited layers was confirmed by a singlelayer deposition efficiency measurement and proved to be a major mechanism in the increment of deposition efficiency of the studied mixtures. Finally, oxide removal produced by the impact of ceramic particles on substrate and deposited layers was evaluated as the complement of the other effects and found to also play a major role in increasing the deposition efficiency. It was found that the coatings retained approximately half of the feedstock powder alumina content. Hardness tests have shown a steady increase with the coating alumina content. Dry wear tests have revealed no improvement in wear resistance in samples with an alumina content lower than 22 wt.% compared to pure aluminum coatings. Adhesion strength showed a steady improvement with increasing alumina content in the feedstock powder from 18.5 MPa for pure aluminum coatings to values above 70 MPa for the ones sprayed with the highest feedstock powder alumina content.
Correlation between Al2O3 particles and interface of Al–Al2O3 coatings by cold spray
Applied Surface Science, 2005
Al-Al 2 O 3 composite coatings with different Al 2 O 3 particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al 2 O 3 ) having different sizes and agglomerations were varied into ratios of 10:1 wt% and 1:1 wt%. Al 2 O 3 particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al 2 O 3 particles. In addition, when the large hard particles of fused Al 2 O 3 were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages. #
Different spray processes for different Al2O3 coating properties
Applied Physics A, 2010
Among the different coating technologies, a thermal spray has a leading position because of its versatility: an extremely wide variety of materials can be deposited to protect back materials from wear, corrosion, thermal flux, etc. For example, atmospheric plasma spray is a rather wellestablished process but some other ones, such as flame technology, can also be used with lower economical impact. After a respective optimization of the processing parameters, both plasma and wire flame thermal processes were tested to form Al 2 O 3 coatings. For each process, in-flight particle conditions, coating cross-section micro-structures and coating properties were successively determined. The experimental parameters were correlated to in-flight particle characteristics and to coating micro-structure and compared to resulting coating features. The evolution of particle velocity and temperature showed well-marked trends and the mean values were dependent on the spray process. The results emphasized the difference of spray system in terms of kinetic and thermal transfers to the particles. Then, the differences observed on in-flight particle characteristics can be used to explain the differences observed in coating properties, such as porosity content and hardness.
Journal of Thermal Spray Technology, 2014
Cold-gas dynamic spraying (''cold spraying'') was used to deposit aluminum-alumina (Al-Al 2 O 3) metalmatrix composite (MMC) coatings onto 6061 Al alloy. The powders consisted of 245 lm commercially pure Al that was admixed with either 10 lm or agglomerated 20 nm Al 2 O 3 in weight fractions of 25, 50, 75, 90, and 95 wt.%. Scanning electron microscopy (SEM), Vickers microhardness testing, and image analysis were conducted to determine the microstructure, properties, and the volume fractions of reinforcing particles in the coatings, which was then converted to weight fractions. As the weight fraction of the Al 2 O 3 in the coatings increased, the hardness values of the MMC coatings increased. A maximum hardness of 96 ± 10 HV 0.2 was observed for the MMC coating that contained the agglomerated 20 nm Al 2 O 3 particles, while a maximum hardness of 85 ± 24 HV 0.2 was observed for the coatings with the 10 lm Al 2 O 3 particles. The slight increase in hardness of the coating containing the agglomerated 20 nm Al 2 O 3 particles occurred in a coating of Al 2 O 3 content that was lower than that in the coating that contained the 10 lm reinforcing Al 2 O 3 particles. The increased hardness of the MMC coatings that contained the agglomerated 20 nm Al 2 O 3 particles and at lower reinforcing particle content was attributed to the increased spreading of the nanoagglomerated particles in the coating, which increased load-sharing and reinforcement capability of the particles. These results suggest that the use of nanoagglomerated, reinforcing hard-phase particles in cold-sprayed MMC coatings may be a more efficient alternative to the use of conventional micronsized reinforcing particles.
The microstructure of alumina coatings prepared by aerosol assisted spray deposition
Surface and Coatings Technology, 2004
This paper presents the deposition of alumina coatings using a low cost aerosol assisted spray deposition (AASD) in an open atmosphere at low temperature. AASD is a variant of CVD, which involves spraying atomized precursor droplets into a heated environment where the droplets undergo decomposition and chemical reaction near the heated substrate and produce solid stable coatings. Using the same deposition method but different starting precursor (e.g. solution or suspension), dense or porous deposits could be produced using the AASD method. Dense and thin alumina coatings were deposited using a precursor solution containing aluminium alkoxide. Whereas thick porous alumina deposits were prepared using a suspension of alumina powder in alcohol solution. Such porous alumina deposits could be densified to form thick alumina coatings. Continuous CO laser was used to 2 densify the alumina deposits. The microstructure of the coatings and deposits was characterized using a combination of X-ray diffraction and scanning electron microscope methods. The dense and porous alumina coatings could be deposited by varying the processing conditions. The relationships between the growth behavior and microstructure of the coatings were also discussed.
Surface and Coatings Technology, 2006
This work describes recent progress in Cold Gas Dynamic Spraying process of conventional and nanocrystalline 2618 (Al-Cu-Mg-Fe-Ni) aluminum alloy containing Sc. As-atomized and cryomilled 2618 + Sc aluminum powders were sieved in two ranges of particle size (below 25 μm and between 25 and 38 μm), and sprayed onto aluminum substrates. The mechanical behavior of the powders and the coatings was studied using the nanoindentation technique, while the microstructure was analyzed using scanning and transmission electron microscopy. The influence of the powder microstructure, morphology and behavior during deposition on the coating properties was analyzed. It was concluded that the hard cryomilled particles do not experience extensive plastic deformation, and therefore failed to form a coating as dense as those produced using the gas-atomized spherical powder, despite the fact that the irregular shape cryomilled particles presented higher flight and impact velocities than the gas-atomized spherical particles. It was also observed that the influence of the particle morphology on the particle velocities is more pronounced for the larger particle size range (between 25 and 38 μm).
Thermal Spray 2021: Proceedings from the International Thermal Spray Conference, 2021
In this study, a novel strategy to manufacture high strength cold-sprayed Al coating by using powder with wide size distribution is proposed. The microstructure and mechanical properties of deposited coating sprayed at three typical impact velocities before and after heat treatment are investigated. Furthermore, the deposition and strengthening mechanisms of the coating sprayed at various impact velocities are clarified. The results show that the coating with higher density and mechanical properties can be successfully fabricated by cold spray at comparatively low particle impact velocity. The mechanical properties were enhanced with the contribution of heat treatment process. It is the in-process tamping effect induced by larger powder that results in the severe plastic deformation thus leads to densification and excellent mechanical properties of the cold-sprayed Al coating.
Journal of Thermal Spray Technology, 2010
Powder type and composition have a very important role in the production of metallic and metallicceramic coatings by using the low-pressure cold spray process. Furthermore, structure and mechanical properties of Cu and Cu + Al 2 O 3 coatings are strongly influenced by powder characteristics of Cu particles. The aim of this study was to evaluate the effect of different particle types of Cu powder and different compositions of added Al 2 O 3 particles on the microstructure, fracture behavior, denseness, and mechanical properties, i.e., hardness and bond strength. Spherical and dendritic Cu particles were tested together with 0, 10, 30, and 50 vol.% Al 2 O 3 additions. Coating denseness and particle deformation level increased with the hard particle addition. Furthermore, hardness and bond strength increased with increasing Al 2 O 3 fractions. In the comparison between different powder types, spherical Cu particles led to the denser and less oxide-contenting coating structure due to the highly deformed particles.
Fabrication of cold sprayed Al-intermetallic compounds coatings by post annealing
Materials Science and Engineering: A, 2006
A cold spray coating technique for thick Al coating with finely dispersed intermetallic compounds was tested by post annealing. The powder composition of Al:Ni and Al:Ti was fixed at 75:25 wt.%. The hard Ni and Ti powders have been successfully coated with the soft metal of Al at low gas pressure condition. Also, the Ni and Ti particles were embedded in the Al matrix. In the post annealing of coatings, the intermetallic compounds were observed in the cold sprayed Al-Ni and Al-Ti composites coatings. Above 450 • C of post annealing temperature, the Al 3 Ni and Al 3 Ni 2 phases were observed in the cold sprayed Al-Ni coatings. The Ni particles in the Al matrix were fully consumed via compounding reaction with Al at the 550 • C of the annealing temperature. In the case of Al-Ti coatings, the Ti particles still existed in the Al matrix up to 630 • C of annealing temperature.
Surface topography, 2022
The aim of this research is to study the comparative wear behaviour of pure Al 2 O 3 with varying TiO 2 content due to the high demand in the industry for high temperature applications such as the automotive industry (piston ring and liner), petrochemicals industry (pump sleeves) and textile industry tools which require the hard bearing surface, abrasion resistance and particle corrosion at the temperature of up to 400 °C. In the present study, three coatings of Al 2 O 3 , Al 2 O 3-13%(TiO 2) and Al 2 O 3-40%(TiO 2) composite coatings were deposited by the thermally ame spray process. The comparative wear behaviour of the Al 2 O 3-TiO 2 coatings has been studied under high temperature of up to 400°C using a high temperature tribometer at a constant load of 40N. Before the wear test, the mechanical properties of the coated samples such as microhardness and surface roughness were studied. The morphological analysis was determined by eld emission scanning electron microscope, elemental dispersion spectroscopy and X-ray powder diffraction techniques. The results reveal that speci c wear rate decreases with a rise in temperature for all the deposited coating except Al 2 O 3 coating at 400°C. The friction coe cient of deposited three alumina based coatings is decreasing with the increasing temperature. The research reveals that the Al 2 O 3-40%TiO 2 coating has the highest wear resistance properties as well as a low coe cient of friction due to its low hardness and high adhesion properties. For Al 2 O 3-40%TiO 2 coating the measured values of speci c wear rate varying from 0.034567*10-3 mm 3 /Nm to 0.014581*10-3 mm 3 /Nm and the average values of coe cient friction ranging from 0.7284 to 0.3901 as temperature varying from room temperature to 400°C. In the worn out surface of deposited coatings, brittle fracture and abrasive wear behaviour were observed from room temperature to 400°C.