Journal of Thermal Spray Technology最新文献

SiC_p/pure Al composites with different SiC_p fractions (20, 30 and 40 wt.%) were cold sprayed followed by hot axial-compression tests at deformation temperatures of 473 K (200 °C) to 673 K (400 °C), leading to failure of specimens through routine crack propagation in their multiphase. The plastic deformation behavior of the coating with respect to the SiC_p contents and the deformation temperatures were studied at strain rate 1 s⁻¹. As-sprayed and post-failure specimens were analyzed by x-ray computed tomography (XCT), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Quasi-static thermomechanical testing results revealed that compressive strength (UCS = 228 MPa) was the highest in the deposits that were compressed at 473 K compared to those of the as-sprayed, while the as-sprayed exhibited a compressive strength of 182.8 MPa related to the increment in SiC_p fractions. Strength-plasticity synergy was promoted by dynamic recrystallization (DRX) through strengthening and refinement of the grains. The DRX degree depends relevantly on grain refinement, higher deformation temperature and the pinning effects of the interfaces promoted by the ultrafine grain structures (UFG). Reconstructed XCT data revealed different crack propagation mechanisms. A single-plane shear crack with multi-laminates fracture morphology yields relatively through the as-sprayed and as-deformed at 473 K deposits, while a multiphase plane shear cracks preeminently existed in high temperature deformed deposits resulting in multiphase-interface delaminations. Three pertinent strengthening mechanisms, videlicet, SiC_p dispersed strengthening, refined grain strengthening and dislocation strengthening existed in the gradient microstructure, and their detailed contributions to the thermomechanical properties were discussed.

Designing and fabricating Fe-based amorphous coatings with excellent wear and corrosion resistance as surface protection materials are essential to improve the service life of marine equipment. In this work, by adding 1 at.% Nb, a novel Fe₃₄Ni₂₀Cr₂₀Mo₅B₄C₄P₁₂Nb₁ high-entropy amorphous alloy with enhanced glass-forming ability and excellent corrosion resistance was designed. The Fe₃₄Ni₂₀Cr₂₀Mo₅B₄C₄P₁₂Nb₁ composition was adopted to prepare gas-atomized powders, which were then used as feedstock to prepare coatings using atmospheric plasma spraying (APS) technology with different input power. Higher spraying power was found to lead to denser coating, but more formation of oxides and lower amorphous content. The coating-35 kW input power exhibited the best corrosion resistance in 3.5 wt.% NaCl solution and high hardness of 519 ± 21 HV. The dry sliding wear rate of the coating-35 kW at 20 N and 20 mm/s was 8.3 × 10⁻⁷ mm³/(N m), and the friction coefficient of the coating was 0.17 and kept relatively steady throughout the sliding test. This work guided designing Fe-based high-entropy amorphous coatings from both the composition aspect and the coating preparation technology.

For the poor working environment, there would easily be sprocket tooth nest corrosion wear failure of mining sprocket, based on coaxial powder feeding method, this study prepares Fe-based alloy cladding on the surface of 42CrMo, which further improves the performance of the substrate. The effects of laser power on the dilution rate, microstructure, hardness and corrosion resistance of Fe-based alloy coating and the effect of heat treatment on the tensile properties of the cladding layer were studied. The results show that, with the increase in laser power, the grain size of the cladding layer becomes larger. When the laser power is greater than 1900 W, the cladding layer generates Fe₂B and Cr₂₃C₆; the average hardness of the coating with laser power of 1600 W is the highest, which is 586.86 HV. Electrochemical experiments show that the 1800 W coating has excellent corrosion resistance, high corrosion potential (− 0.42 V) and minimum corrosion current density (2.65 × 10⁻⁶A·cm⁻²). EDS results show that no obvious corrosion area is found on the surface of the 1800 W cladding layer. This excellent performance is attributed to the formation of a dense Cr₂O₃ passivation film on the surface of the cladding layer. The tensile test shows that the coating heat treated at 700 °C has the best tensile properties.

Traditional optimization of plasma-sprayed coatings involves resource-intensive experimental iterations of spraying parameters. This study presents a novel computational protocol for designing and manufacturing ceramic (e.g., Al₂O₃) coatings, reducing the need for extensive experiments. A computational fluid dynamics approach is adopted to simulate the morphology of Al₂O₃ powder feedstock splats. These simulated splats are then stochastically arranged to construct three-dimensional (3D) representations of plasma-sprayed Al₂O₃ coatings. The effective elastic modulus of the coating is computed using finite element analysis of the simulated microstructure. The introduced "Desktop Manufacturing Protocol" showcases a significant reduction in the requisite plasma spraying experiments, offering an optimized coating with desired microstructure and mechanical properties. This integrated computational approach not only streamlines the coating development process but also provides insights into the intricate relationships between spraying parameters, microstructure, and overall coating performance.

The thermal conductivity of thermal barrier coating (TBC) materials can be measured using transient and steady-state methods. It is crucial to evaluate the high-temperature thermal insulation performance of TBC materials. Although several steady-state methods exist for obtaining in situ TBC thermal conductivity at high temperatures, they are limited by heating methods and heat flux measurement instruments. In this study, a transient-state method is proposed, which does not have these limitations. Numerical simulations indicate that this method accurately predicts the temperature-dependent thermal conductivity of TBC materials in situ. The experimental results align well with existing literature. This method has potential applications for monitoring TBC failures, such as sintering, cracking, and peeling.

High entropy alloys (HEAs) are the recent category of metallic alloys that exhibit superior properties, especially in extreme working environments, when compared to conventional metal alloys. Their advanced properties make them suitable candidates for various structural and functional applications as surface coating and additively manufactured components. Thus, the suitability of various deposition and fabrication techniques are being explored, taking into consideration the material’s multi-component composition. Among various manufacturing techniques, cold spray has significant merits when handling HEAs. This review is aimed at providing a detailed state of the art of cold-sprayed HEAs. The microstructure evolution after cold spray, as well as the function and performance in terms of wear resistance, mechanical strength, corrosion resistance and oxidation resistance of the deposits are discussed for all cold spray deposits of HEAs. The reported post-treatments applied to HEAs deposits and their effects on functionality are also discussed to help us lay a base for further investigations and developments in the new horizon of HEAs. Perspectives on potential future developments are discussed to provide directions for research investigations in the field of cold spraying of HEAs.

This study investigates metal matrix composites fabricated by cold spraying nickel (Ni) as the matrix with two different chromium carbide/nickel chrome (CrC/NiCr) cermet powder formulations as the reinforcement onto A514 steel. The research focuses on understanding the effects of the metallic binder (NiCr) ratio in the cermet particles and the matrix-to-cermet (i.e., Ni-to-CrC/NiCr) ratio in the feedstock blend on the microstructure and mechanical properties of the resulting composites. The microstructure of the as-received powders and the cold-sprayed deposits was analyzed using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) techniques, while the mechanical performance of the deposits was evaluated using microhardness, tensile, and triple-lug shear tests. Results indicate that increasing the binder percentage in the cermet particles enhances deposition efficiency, leading to a higher area fraction of the retained cermet in the final deposit, improved interparticle adhesion, reduced porosity, and superior ductility and shear strength. The study also identifies three distinct crack propagation patterns that explain the variations in fracture behavior among different MMCs and metallic deposits. These patterns are governed by the extent of cracking in the cermet particles and the interparticle bonding strength, which in turn affect the ultimate tensile strength (UTS) of the coatings.

Thermal spraying effectively enhances the surface properties of titanium alloys, yet the required surface roughening by grit blasting (GB) often degrades fatigue performance. This study proposes shot peening (SP) prestressing prior to GB to create a crack extension inhibition zone, thereby enhancing fatigue resistance. Simulations and experiments demonstrated that SP prestressing generates high compressive stress (~900 MPa) up to a depth of ~ 200 µm, which helps to alleviate the stress concentrations caused by these sharp protrusions from GB. Consequently, crack propagation is inhibited, preserving the fatigue strength of SP-pretreated, thermally sprayed TC4 alloys, while untreated counterparts show a 20% reduction in fatigue limit. Additionally, SP prestressing followed by GB maintains a high coating bond strength (>60 MPa). These findings advance the application of thermally sprayed titanium alloys in aerospace engineering.

Proton exchange membrane water electrolysis is currently a promising technology in the hydrogen production industry. However, the high cost of titanium bipolar plates is one of the market penetration limitations. This study explores the conductivity and corrosion resistance of Ti₄O₇ by employing Ar+H₂ and Ar+He as the spraying gases for the preparation of Ti₄O₇ coatings on an SS316L substrate using atmospheric plasma spraying and low-pressure plasma spraying methods at different power levels (10, 17.5, and 25 kW). The objective is to investigate the effects of various spraying conditions on the phase composition, microstructure, corrosion resistance, and conductivity of the Ti₄O₇ coatings. The results indicate that the surfaces of the coatings obtained via low-pressure plasma spraying were confirmed to be Ti₄O₇, with a presence of Ti₃O₅ on the coating surface, while the coatings from atmospheric plasma spraying primarily comprised TiO₂. Electrochemical measurements demonstrate that the coating produced by low-pressure plasma spraying at 17.5 kW exhibited excellent corrosion resistance in a simulated anode corrosion environment of the proton exchange membrane water electrolysis cell, providing superior protection for the SS316L bipolar plates. Furthermore, the coating applied at 25 kW exhibited the highest conductivity.