Journal of Thermal Spray Technology最新文献

The coatings with high hardness, good machinability and geometric accuracy show great potential applications in steel industry. In this work, age hardening steel (Fe-(Co,Ni)-(W,Mo))-based coatings strengthened by TiC were fabricated on H13 steels by argon arc cladding using prefabricated blocks. The (Fe-Co-Mo)-TiC coatings show good bonding properties and low hardness after cladding. After direct aging treatment, with the decomposition of supersaturated solid solution and the precipitation of intermetallic compounds (μ-phase), the hardness rapidly increased to more than 827 HV_0.5. The hardness and oxidation resistance of FeCoMo-TiC layers can be further enhanced by the introduction of W and the corrosion resistance of the layers can be modified by adding Ni. This study enriches the knowledge about the application of age hardening steels in the field of coatings.

In this paper, the design, microstructure characterization and friction properties of in situ synthesized TiC-reinforced Fe-based composite coatings by powder-assisted wire arc surfacing were studied. TiC-reinforced Fe-based surfacing layer was successfully prepared by surfacing on Mn13 substrate with 1Cr17 solid core stainless steel wire and self-developed Fe-based alloy powder. The results show that TiC particles are successfully synthesized in situ and uniformly distributed in the surfacing layer. The microstructure analysis shows that TiC particles, as the core of non-spontaneous nucleation, refine the grain structure and play a stirring role in the molten pool, which destroys the dendrite growth and optimizes the microstructure of the coating. The presence of TiC significantly improved the microhardness of the coating, and the average hardness reached 650.0 ± 25 HV, which was significantly higher than that of the substrate. In the dynamic load abrasive wear test, the wear resistance of the surfacing sample is better than that of the Mn13 steel substrate, and the wear amount is significantly reduced under different impact energies. In addition, the friction coefficient of the surfacing layer is lower than 0.4 and relatively stable, and the friction performance is significantly improved. This study provides a theoretical basis and experimental support for the preparation of high-performance coatings by solid wire combined with powder surfacing.

Since powder selection for in situ synthesis by laser cladding is rarely studied at present. To remedy this deficiency, a powder selection method was proposed. TiC/TiB₂ composite coatings were synthesized by laser cladding Fe-based, Ni-based, and Co-based powders with added Ti/B₄C on D2 die steel. The properties of the coatings after laser cladding of the three schemes were analyzed and evaluated. The average microhardness of Fe-based composite coatings was the largest at 708.3 HV_1.0, while the average microhardness of Ni-based composite coatings was the lowest. Meanwhile, the Fe-based composite coating had the best wear resistance with only 9.8 mg of wear, but the Fe-based composite coating had the worst toughness with a elongation of only 2.61%. The microhardness, wear resistance, tensile, and impact toughness of the Co-based coating were in between. Finally, the three coatings were scored by entropy weight method combined with technique for order preference by similarity to an ideal solution, and the Co-based composite coatings had the highest score of 0.625, which proved that it had the best comprehensive performance and was more suitable for in situ synthesis of composite coatings with TiC/TiB₂ particles.

Ceramic coating prepared by laser cladding is an effective methods for enhancing the surface properties of materials, where the process parameters directly influence the quality characteristics of the coating formation. To investigate the effects of the process parameters on the quality characteristics of Ti(C,N) ceramic coatings prepared by laser cladding on the Ti6Al4V substrate, a mathematical model was developed to establish the relationship between the process parameters (laser power, scanning speed, and overlapping ratio) and the quality characteristics (thickness, width, and microhardness) using the response surface methodology. Additionally, the optimal process parameters were determined through multi-objective optimization using the overall desirability function. Finally, the microstructure and properties of Ti(C,N) ceramic coatings prepared by laser cladding under optimized process conditions were further analyzed. The results showed that the mathematical model linking the process parameters to the quality characteristics exhibited high predictive reliability. The laser power and overlap rate were the crucial process parameters for the quality characteristics of Ti (C, N) ceramic coatings. The optimal process parameters based on the multi-objective optimization were as follows: laser power of 853.09 W, scanning speed of 8.18 mm/s, and an overlap rate of 40%. The Ti(C,N) ceramic coating prepared by laser cladding comprised TiC_0.3N_0.7 with equiaxed grains, Ti₃Al intermetallics, and α-Ti. The microhardness and wear volume of the coating were 1064.87 HV_0.2 and 4.44 × 10⁶ μm³, respectively. Its friction coefficient decreased by 56.97% compared to the substrate. The wear mechanisms of the coating were slightly abrasive wear and oxidative wear. The tribological properties of the Ti6Al4V substrate surface were significantly improved by the TiC coatings. This work advances the research on the process parameters of the high-quality ceramic coatings prepared by laser cladding.

As the core power device in modern industry, the cylinder sleeve—a key engine component—endures high temperatures, high pressures, and wear. Applying high-performance coatings via laser cladding with optimized parameters effectively improves wear and corrosion resistance. The results indicate that the NiCr coating produced at 1400 W laser power exhibits the highest quality, with a porosity of 0.36%, and primarily consists of γ-(Ni, Cr), γ-(Ni, Fe), and Ni_2.9Cr_0.7Fe_0.36 phases. As the laser power increased from 1200 W to 2000 W, the wear scar depth of the coating gradually decreased from 28.4 μm to 27.2 μm, and then increased to 33.5 μm. The NiCr coating exhibited an initial decrease followed by an increase in both friction coefficient and wear rate, reaching their lowest values at 1400 W. At this power, the coating exhibits a minimum wear rate of 1.47 × 10^-5 mm³/(N·m), with abrasive wear and adhesive wear being the predominant mechanisms. The 1400 W NiCr coating exhibited the fewest fatigue cracks and adhesive wear marks, with its uniform grain distribution effectively reducing plastic deformation during friction and improving tribological performance.

The development of thermal spray coatings for specific industrial and scientific applications is critical, particularly in the context of sustainable and economical production. This study employs a hybrid experimental–statistical approach to identify the influence of key process parameters and their interactions, based on a systematic design of experiments. Five factors were investigated: total gas flow (TGF), fuel-to-oxygen ratio (F2O), powder feed rate (PFR), standoff distance (SOD), and coating velocity (CV). The effects of these factors on in-flight particle properties, process performance, and coating characteristics were analyzed. Nondestructive evaluations, including deposition efficiency, surface roughness, and surface hardness, were directly compared with microstructural measurements. In contrast to previous studies, TGF emerged as the most influential parameter, exerting a stronger effect on particle properties, process performance, and coating characteristics than F2O. Significant interactions were identified, including the combined effects of TGF and F2O on roughness and hardness, TGF and PFR on deposition efficiency, and TGF and SOD on surface roughness. This investigation advances beyond validating known correlations by uncovering nuanced multidimensional interactions, offering a robust framework for optimizing WC-CoCr coatings. The findings contribute to the broader objective of enhancing the performance and sustainability of modern coating technologies through nondestructive methodologies.

To further enhance the AlCoCrFeNi high-entropy alloy (HEAs) coatings prepared by plasma spraying, laser remelting was employed to process the surface. This study investigates the differences in microstructure and the changes in properties between the laser-remelted coatings and the as-sprayed coatings. The results indicate that the laser-treated coating is composed of BCC phase and a small amount of α-Al₂O₃, forming a good metallurgical bond with the substrate. The layered structure of the sprayed coating has been eliminated, with grains rearranged and grown anew, resulting in an increase in hardness from 453.2 HV_0.2 to 591.5 HV_0.2. In electrochemical tests, the remelted coatings had higher corrosion potentials and lower self-corrosion current densities. After XPS testing, the passivation film of the remelted coating exhibits high intensities of Cr₂O₃ and Fe₂O₃. After laser remelting, pores and cracks in the coating are basically eliminated, the microstructure becomes more uniform and denser, and the hardness and wear resistance of the coating are significantly improved; the reduction in coating defects decreases the likelihood of corrosion, enhances the uniformity of the passivation film on the coating surface, and thereby improves the corrosion resistance of the coating. In summary, the laser remelting process can effectively enhance the coating by improving the microstructure of the sprayed coating, thereby enhancing its overall performance.

The quality of low-pressure plasma-sprayed tungsten (W) coatings for application in fusion reactors was investigated under various spray process parameter settings for the following substrate materials: carbon fiber composite, Eurofer (a ferritic/martensitic steel with reduced activation), and tungsten. The deposited coatings with a thickness of approximately 130 µm were evaluated in terms of porosity, deposition efficiency, defects, and surface roughness. Selected parameter sets were applied to produce scaled-up coatings up to 500 µm in thickness on Eurofer and tungsten substrates. Regions of very low porosity of approx. 0.3% and varying grain appearance were found. However, the subsequent grain size evaluation in terms of the aspect ratio of the fitted ellipse and the maximum Feret diameter did not reveal any significant differences in grain structure through the coating regions. The residual stress measurements performed by XRD using the sin²(Ψ) method validated the thermal stresses within the coatings resulting from the thermal mismatch between the coating and the substrate during cooling. The results indicate that the process settings and spraying process were effective in reducing residual stresses and producing coatings suitable for future fusion-relevant applications.

High-entropy rare-earth tantalates have potential for use in thermal barrier coatings, but current research has focused mostly on powder or bulk materials instead of coatings. In this work, atmospheric plasma spraying technology was employed to prepare novel high-entropy rare-earth tantalate (Nd_0.2Dy_0.2Ho_0.2Y_0.2Er_0.2)TaO₄ (HE-RETaO₄) coatings on the surface of nickel-based alloys. The as-sprayed HE-RETaO₄ powders undergo a ferroelastic phase transition from the monoclinic (m) phase to the metastable tetragonal (t′) phase during the spraying process. Owing to the influence the cationic radii of multispecies HE-RETaO₄, its phase transition temperature is lower than that of YTaO₄, leading to the formation of a ferroelastic domain toughened structure at lower temperatures. Under the plasma flame assessment at 1200 and 1300 °C, the insulation temperatures of the HE-RETaO₄ coatings are 220 and 200 °C, respectively. The sluggish diffusion of HE-RETaO₄ hinders diffusion of elements, ultimately engendering a profusion of equiaxed grains with comparable aspect ratios and a substantial divergence in energy between intragranular regions and boundaries. In addition, the microcracks generated within the HE-RETaO₄ coatings rapidly expand along the high-energy grain boundaries of the equiaxed grains, eventually leading to mechanical delamination and coating failure. This work provides a powerful theoretical basis for the application of HE-RETaO₄ as a high-temperature protective material.

To study the feasibility of low-cost repair of the casting and service defects of magnesium alloys, Al coatings were deposited on ZM6 substrates using an in situ micro-forging cold spray (MF-CS) process. Large-size 410 stainless steel (410SS) MF particles are mixed into Al powder during spraying to promote the plastic deformation of Al layer and form dense coatings. The effects of cold spray process parameters on the quality of Al coatings were investigated, and the optimal process parameters are obtained. The experimental results show that the porosity of Al coatings decreases with the increase of MF particle content. When the MF ratio is greater than 40 vol.%, the microstructure of Al coatings is dense and the porosity is lower than 0.1%. As the content of MF particles further increases, the micro-hardness of the Al coatings slightly increases to 51.91 HV_0.1, and the bonding strength increases to 126.3 MPa. The sealing performance test shows that the optimal spraying angle is 15°, where the coated specimen can withstand a maximum pressure of 1 MPa for over 10 minutes. The electrochemical measurements show that the Al coatings prepared with the MF content greater than 40 vol.% exhibit good corrosion resistance. The presence of small amount of MF particle remnants (< 2.8%) in the Al coatings does not present significant galvanic corrosion effect. The oxidation film on the surface of the coating and the tight bonding between particles hinder the corrosion of the corrosive medium on the inside of the Al coatings and improve the pitting behavior. This study verifies the feasibility of cold spray technology in the repair of magnesium alloy parts in the aerospace sector.