Journal of Thermal Spray Technology最新文献

In the present work, tribological mechanisms under different sliding wear parameters, viz. applied load, sliding speed, and sliding distance, have been investigated in an Fe-based amorphous/ nanocrystalline coating synthesized by atmospheric plasma spraying. To understand the role of different wear parameters, Taguchi method was employed to design the experiments, and the results were analyzed using analysis of variance. The results revealed that sliding speed is the most significant contributing factor for wear rate of Fe-based amorphous/ nanocrystalline coating deposited by atmospheric plasma spraying process. A comprehensive understanding of influence of the sliding parameters on the wear process was understood based on different wear mechanisms. It was found that low sliding speeds resulted in predominantly abrasive wear, while high sliding speed led to mainly fatigue wear with a minor amount of abrasive wear. Interestingly, alterations in applied load and sliding distance did not induce a transformation in the wear mechanism itself; rather, they manifested in variations in the severity or extent of the wear mechanism. Increase in sliding speed and applied load led to an increase in the extent of wear loss, which was correlated with flash temperature on the coating surface and kinetic energy of the countermaterial during the wear process. On the contrary, increase in sliding distance caused a decrease in wear rate of the coating.

N-doped CoCrFeNiMn high entropy alloy coating (N-HEA) was prepared on Ti-6Al-4V alloy by high-velocity oxygen fuel (HVOF) spraying coupled with double glow plasma nitriding. The results show that the CoCrFeNiMn high entropy alloy coating (HEA) is mainly composed of single CoCrFeNiMn face-centered cube (fcc) phase with a little MnCr₂O₄ spinel phase, and the thickness is approximately 200 μm. After plasma nitriding, the surface morphology of the coating is reconstructed, changing from the molten and semi-melted coral-like structure to cauliflower-like structure, while the surface roughness and the thickness have no significant change. The phase composition of the N-HEA coating has no obvious change, and the N mainly exists as interstitial atoms in solid solution. The microhardness of the HEA coating is highly significantly higher than Ti-6Al-4V alloy, and it is further increased by 45% after plasma nitriding. The friction coefficient of N-HEA coating is as low as 0.38, and the wear rate is 1.283 × 10⁻⁴ mm⁻³N⁻¹ min⁻¹, which is 53 and 72% lower than those of the HEA coating and the Ti-6Al-4V alloy, respectively. Both the wear mechanism of the N-HEA and HEA samples against GCr15 steel ball are mainly adhesive wear, while more Fe elements are transferred from the GCr15 steel ball onto the surface of the N-HEA sample.

This paper introduces novel possibilities of using recently developed high-power lasers for high-speed surface periodic structuring/patterning of the ceramic substrates for the subsequent thermal spray coating deposition, which may be difficult to pattern using conventional methods. Yttria-stabilized zirconia (YSZ) was selected as model ceramic for both substrates and coating. Three different types of patterns were produced by three different laser technologies: dimples with nominal depth of 15 and 30 µm (pulsed nanosecond laser), grids with nominal depth of 15 and 30 µm (continuous wave laser), and pillars with nominal depth 30 µm (ultrashort pulsed femtosecond laser). All surface patterns were thoroughly periodical and their surface roughness ranged from S_a = 4.5 to 10.3 µm, significantly surpassing conventional grit-blasting. Pulsed and continuous wave lasers showed very high process rates (up to 54.5 mm²/s and 323.6 mm²/s, respectively) and tendency to develop network of shallow surface cracks. Ultrashort pulsed laser technology was slower (process rate 1.65 mm²/s) but the surface was crack-free with desirable miniature anchoring points. Plasma spraying was carried out with powder, solution, and suspension feedstocks providing an experimental matrix demonstrating potential benefits and risks of each pattern-feedstock combination. Not all combinations led to successful coating deposition, but results show that microstructure of the coating may be deliberately controlled by laser texturing, in particular periodic substrate pattern led to periodic coating microstructure in the case of suspension spraying. Also adhesion/cohesion of the coating to the substrate may be in many cases significantly improved by laser patterning of the substrate. The highest coating adhesion/cohesion strength (26.2 ± 4.8 MPa) was achieved for the coating deposited from solution on pillar patterns. Finally, a possibility to combine the high-speed and advanced surface morphology produced by continuous wave and femtosecond lasers, respectively, and direct patterning of plasma sprayed coating were also demonstrated.

Graphical Abstract

Obtaining excellent wear and corrosion resistance for Mg alloy is of great significance. In this study, Al_0.5MnFeNiCu_0.5Si_x coatings were prepared on Mg alloy by laser cladding. To relieve the stress gradient between Mg alloy and Al_0.5MnFeNiCu_0.5Si_x coatings, Al-Ni alloy was selected as the transition layer. The effects of Si content on the microstructure, wear and corrosion resistance of Al_0.5MnFeNiCu_0.5Si_x coatings were analyzed. The results showed that Al_0.5MnFeNiCu_0.5Si_x coatings exhibited the equiaxed grain composed of BCC and FCC. Compared with Mg alloy, the microhardness of Al_0.5MnFeNiCu_0.5Si_x coatings was improved by 7.2 to 11.06 times, and the wear volume was decreased by 87.82-94.98% because of the comprehensive effect of solid solution strengthening, dislocation strengthening and fine grain strengthening. Al-Ni transition layer inhibited the dilution of Mg into Al_0.5MnFeNiCu_0.5Si_x coatings and reduced the corrosion potential difference. Moreover, Al_0.5MnFeNiCu_0.5Si_0.75 coating had the best wear resistance and corrosion resistance due to low segregation rate of Al, Cu and the fine grain.

PEEK surface copper metallization is widely used in fields such as power, electronics, and new energy. To enhance the mechanical and electrical characteristics of copper coating on PEEK surface further, this study employed a cold spraying deposition technology of graphene-reinforced copper composite coatings. The investigation focused on the properties comparison between composite coatings and pure copper coatings, and systematically studied the influence of nozzle speed within the range of 50–200 mm/s on the structure and properties of composite coatings. Results show that the mechanical and electrical properties of composite coatings are far superior to those of pure copper coatings. And results indicate that at a nozzle speed of 100 mm/s, the composite coating exhibits the densest structure, with a porosity of 0.31% and minimal graphene aggregation, resulting in superior mechanical and electrical properties. Specifically, the friction coefficient is reduced by 46.81% compared to pure copper coating, measuring 0.4046. Additionally, the Vickers hardness of the composite coating reaches 105.96 HV, and its wear rate is 70.59% lower than that of pure copper coating, at 4.32·10⁻⁴ mm³/N·m. Furthermore, the conductivity peaks at 1.295·10⁵ S/cm, representing a 38.77%, increase over pure copper coating.

Due to its similar Young’s modulus to bone, polyetheretherketone (PEEK) shows potential as an alternative to metallic implants, avoiding the stress-shielding effect. Hydroxyapatite (HAp) coatings promote bone growth on the implant surface, while zinc oxide acts as an antibacterial agent. This study aims to develop functional coatings on PEEK that simultaneously stimulate bone growth and exhibit antibacterial properties. ZnO-doped HAp coatings were applied to PEEK using a powder mixture of ZnO/HAp and hybrid process (atmospheric plasma spraying and solution precursor plasma spraying). With powder mixtures, the ZnO content in the coatings could be determined without phase change, with nearly half of the initial ZnO powder lost. Meanwhile, using hybrid methods, the aerosol precursor zinc nitrate couldn’t fully convert into zinc oxide, resulting in the presence of intermediate zinc hydroxynitrate (up to 39.38%) in the as-sprayed coatings. Subsequently, the zinc hydroxynitrate could be converted to zinc oxide after heat treatment.

In this study, the effect of an in situ shot peening and cold spraying process for depositing niobium using nitrogen gas was studied and compared to that of traditional niobium sprayed using helium gas. The samples were evaluated using Vickers hardness indentation and defect analysis to compare the mechanical properties and microstructure of the shot-peened samples with that of the helium-sprayed samples. During this study, a mathematical model was proposed to effectively predict the amount of shot peening required to achieve a specific increase in sample hardness. A novel means of using two cold spray systems was also proposed to obtain a better level of control during the shot-peening process. It was found during this study that in situ shot peening can be used to increase the as-sprayed hardness and density of nitrogen-sprayed niobium cold spray deposits to levels comparable to niobium cold sprayed using helium gas. This offers a potential means to transition away from the use of helium gas without sacrificing material properties.

With the high interest in aerosol deposition in order to form high-quality coatings by solid-state impact, there is an increasing demand for developing general guidelines to estimate needed particle velocities and thus process parameter sets for successful deposition of ceramic materials. By using modeling approaches, rather different material properties in first instance can be expressed in terms of binding energies. Needed velocities for possible bonding can then derived by impact simulations and compared to experimental results from the literature. In order to study the role of binding energy on the impact behavior of ceramic particles in aerosol deposition, a molecular dynamics study is presented. Single-particle impacts are simulated for a range of binding energies, particle sizes and impact velocities. The results show that increasing the binding energy from 0.22 to 0.96 eV results in up to three times higher characteristic velocities corresponding to the threshold of bonding or grain size-dependent fragmentation of the particles. However, regardless of the binding energy, exceeding the characteristic velocities results in a similar deformation and fragmentation pattern. This allows for a general representation of the impact behavior as a function of normalized impact velocity for different ceramic materials. Apart from dealing with prerequisites for bonding of different materials by aerosol deposition, this study could also be generally relevant to the high-velocity deformation behavior of ceramics with different grain sizes.