Journal of Thermal Spray Technology最新文献

Polyether ether ketone (PEEK) nanocomposite coatings with diverse dimensional carbon nano-fillers to achieve low friction and low wear of moving mechanical parts in severe application conditions were not the same as the bulk polymer nanocomposites due to their special manufacturing processes. Herein, the flame spray processes were utilized to fabricate the PEEK and carbon fibers/PEEK (CFs/PEEK) nanocomposite coatings with one-dimensional carbon nanofibers (CNFs), two-dimensional graphene nanosheets (GNSs) and three-dimensional graphite nanoparticles (GNPs) in contents of 1.0 and 5.0 wt.%. The CNFs, GNSs and GNPs in low content restricted the formation of large voids in flame-sprayed CFs/PEEK nanocomposite coatings. The introducing of three kinds of carbon nano-fillers aggravated the thermal degradation of PEEK matrix in flame-sprayed PEEK and CFs/PEEK nanocomposite coatings. The specific wear rates of CNFs/CFs/PEEK, GNSs/CFs/PEEK and GNPs/CFs/PEEK nanocomposite coatings were one order of magnitude below those of CNFs/PEEK, GNSs/PEEK and GNPs/PEEK nanocomposites coatings. The incorporation of one-dimensional CNFs with superior mechanical properties reduced the fatigue and adhesive wear of nanocomposite coatings. The large voids aroused by the agglomeration of two-dimensional GNSs aggravated the wear loss of nanocomposite coatings. The three-dimensional GNPs with high graphite degree preserving the superior lubrication effect exhibited the enhanced lubrication role in nanocomposite coatings.

This study investigates the effect of wire diameter (Φ = 1.2, 1.6, and 2.0 mm) on the microstructure and properties of Al-based coatings deposited via plasma-enhanced high-velocity arc spraying onto steel substrates. The microstructure, mechanical properties, and electrochemical behavior of the resulting coatings were systematically characterized, with a focus on investigating the influence of wire diameter on the microstructural evolution, mechanical performance, and corrosion resistance of the coatings. The results demonstrate that an increase in wire diameter leads to the formation of larger molten droplets during the melting and atomization process, which in turn affects the droplet spreading behavior and the overall coating structure. While the phase composition of the coatings remains unaffected by the wire diameter, both surface roughness and porosity initially decrease and subsequently increase, achieving the lowest values at a wire diameter of Φ1.6 mm. The microhardness and bonding strength exhibit a slight fluctuation, showing an initial increase followed by a decrease; however, the overall variation is minimal, with average values of approximately 35 HV 0.1 and 37 MPa, respectively. Electrochemical analysis reveals that the corrosion resistance of the coatings is strongly influenced by their surface morphology and internal density. The corrosion resistance ranking is as follows: Φ1.6 mm > Φ1.2 mm > Φ2.0 mm. Among the tested diameters, the coating fabricated using Φ1.6 mm wire demonstrates the best overall performance.

This work presents the development of cobalt-base/chromium/molybdenum/silicon superalloys coatings, by flame thermal spray on pipeline carbon steel substrates. The coatings were developed at 9 cm, 11 cm and 13 cm, to calibrate the most appropriate thermal spray distance, with the aim to obtain high-quality coatings. The microstructures, bonding, internal porosity and mechanical properties of the coatings were analyzed to stablish coatings properties. Energy-dispersive spectroscopy (EDS), x-rays diffraction and mapping analyses were performed to determine coating’s microstructure. Three-point bend tests of substrates coatings were performed to evaluate coating’s bonding properties and fracture behavior. The results showed good coating’s adhesion on steel substrates. Micro Vickers hardness tests were also performed to measure the hardness of the developed and high Vickers values were obtained, with scatter in all coating’s conditions. The results showed that the best thermal spray distance is 11 cm, to obtain high quality, along with other thermal spray parameters. At this thermal spray distance, the porosity and oxides were reduced; the lamellas were more consolidated, the hardness were less scattered. The coatings will be employed to protect oil and gas subsea production systems, against corrosion derived from the content of H₂S and CO₂ in oil and gas.

To investigate the molten pool dynamics and defect formation mechanisms during the laser cladding of FeCoNiCrMo high-entropy alloys on Ti6Al4V substrates, a three-dimensional coupled temperature and flow field model for a single-track cladded coating was established. The influence of varying laser energy densities (80, 90, 100, 110, and 120 J/mm²) on the geometric characteristics of the cladded coating was systematically analyzed to elucidate the relationship between processing parameters and cladding morphology. The results reveal that the presence of pronounced Marangoni convection significantly influences the morphological characteristics of the FeCoNiCrMo cladded coating. At a laser energy density of 120 J/mm², the molten pool flow velocity reaches up to 48 mm/s, leading to the maximum observed values of cladded layer dimensions. Conversely, at a lower energy density, the molten pool demonstrates limited flowability and promotes bubble entrapment at the solidification front and contributes to the formation of porosity defects. Elevated laser energy densities (Led = 110 and 120 J/mm²) were observed to enhance the dilution rate of the cladded coatings, thereby promoting the diffusion of alloying elements from the molten pool into the Ti6Al4V substrate. However, the increased energy input also led to higher residual tensile stresses within the cladded coatings, which serve as a driving factor for crack initiation at the fusion interface between the substrate and cladded materials.

This paper systematically investigates the impact of cold spraying temperature on the microstructure and high-temperature oxidation resistance of Cr coatings. Three types of Cr coatings are prepared using different temperature parameters. The results show that as the spraying temperature increased from 500 to 700 °C, the average grain size decreased from 3.4 to 0.5 μm. The refinement of grains promoted the rapid formation and continuous growth of the Cr₂O₃ oxide layer by increasing the grain boundary density. The study reveals the mechanism by which cold spraying temperature optimizes the oxidation resistance of coatings through the regulation of grain size.

This study investigates the use of cold spray additive manufacturing (CSAM) to fabricate Permalloy ferromagnetic components using two ferromagnetic iron-nickel FeNi50 alloy powders with particle sizes of D50 = 13 µm and 35 µm. By varying spraying distance and gas temperature, the research evaluates how process parameters influence deposition efficiency, microstructure, and functional properties. The highest deposition efficiency (62%) was achieved using the coarser powder at 640 °C and 35 mm distance. Microstructural analysis showed compact, low-porosity deposits, with the fine powder reaching porosity below 1%. All samples retained the FCC γ-phase structure of the feedstock without forming new phases. Microhardness was highest near the substrate, with the fine powder reaching 247 ± 5 HV. Magnetic characterization revealed superior performance from coarse powders, with higher saturation magnetization (1.06 T), lower coercivity (2239 A/m), and higher permeability (653), while fine powders led to increased magnetic losses due to ultrafine grains and internal defects. Overall, CSAM demonstrates strong potential for producing soft magnetic Permalloy components with tunable properties, particularly when using coarser powders.

This study investigates the relationship between microstructure, hydrogen diffusion, and corrosion resistance in cold sprayed (CS) 410L stainless steel (CS410L). Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used for microstructural analysis, while electrochemical methods assessed hydrogen transport and corrosion performance compared to wrought 410L (W410L). Although studies on the hydrogen trapping steels exist in literature, understanding the influence of the CS microstructure on hydrogen diffusion is crucial before implementation. Analysis of the CS microstructure revealed grain refinement at prior particle boundaries (PPB), while grains among the interior remained coarse though highly strained. Hydrogen permeation results indicated a significant drop in diffusivity in CS deposit, due to increased defect density and heterogenous microstructure. Significant hydrogen trapping at PPB was revealed by silver decoration in CS deposit, while trapping in W410L occurred at precipitate/matrix interfaces. Electrochemical results of CS410L exhibited no passivity and corroded actively in 0.1 M NaCl, while W410L exhibited passivity. Immersion studies demonstrated corrosion initiation and significant propagation along PPBs in CS deposit, in contrast to limited surface degradation in W410L. However, under high alkaline conditions (pH > 12) CS410L exhibited a comparable corrosion performance. Findings highlight CS-induced microstructural defects govern both hydrogen transport and corrosion resistance.

In this study, addressing the challenge of poor mechanical properties in cold spray additive manufacturing (CSAM) deposits, typical thermal-mechanical effects (Friction stir processing-FSP and Hot rolling-HR) were introduced into the deposit. The results indicate that multiple passes of FSP can eliminate defects caused by poor flow within the deposit, resulting in an initial decrease followed by an increase in porosity. However, the bonding quality between metal and ceramic deteriorates after three passes of FSP. Post-FSP, there is an increased disparity in microstructure, with smaller grain size and lower dislocation density observed on the advancing side compared to the retreating side, while the precipitates in the stir zone approaches the solid solution state. The optimal mechanical properties of the deposit are achieved at a traverse speed of 150 mm/min and a rotational speed of 1000 rpm, with a 43% increase in tensile strength and tensile strength and elongation reaching 406 MPa and 2.7%, respectively. After HR, the tensile strength and plasticity of the deposit increased to 439 MPa and 3.93%, respectively. The fundamental reasons for the mechanical property improvement of HR and FSP are both the conversion of mechanical interlocking between particles into metallurgical bonding.

Marine equipment continues to face the threat of marine biofouling, and the large-scale preparation of antifouling coatings using thermal spray technology has been emerging as one of the effective strategies. Polyimide coatings were prepared by flame spraying precursor liquid materials, and the spraying distance and substrate temperature were altered to obtain optimal coating structure. A novel antifouling agent NH₂-ZIF-8@BITEP was synthesized by using a zinc-based metal-organic framework ZIF-8 as a nanocarrier to bond epoxidized BIT. This antifouling agent was mixed with polyamide solution, and the MOF-based coatings were fabricated via flame spraying. The coating showed a sterilization rate of over 99.99% after co-incubation with Escherichia coli and Staphylococcus aureus for 24 h, and effectively reduced the adhesion of diatoms after 14 days of co-culturing. This new MOF-loaded polyimide coating would open a new window for designing and constructing marine antifouling coating for long-term applications.

Severe-service materials in cracking reactors face complex corrosion-fouling phenomena driven by sulfur-rich heavy oil. Nickel-based alloys (Inconel 718—IN718) and cobalt-based coatings (Wallex 50—W50) are common materials in petrochemical equipment, but their degradation behavior under heavy oil cracking conditions is seldom explored. Bare IN718 and high-velocity oxygen fuel (HVOF) sprayed W50 were exposed to cracking environments—445 °C and > 11 MPa, varying hydrogen, catalyst, and agitation—simulating realistic refinery environments. Optical imaging of the surface allowed to semi-quantitatively assess the surface fouling intensity, while SEM-EDS analysis of cross-sections and surfaces offered new perspectives about the sulfidation mechanism, and XRD identified oxides and sulfides in the degradation scale. W50 formed scales with reduced coke accumulation, especially on smoother surfaces. In contrast, IN718 developed more unstable, delaminating scales with severe grain boundary corrosion, particularly under catalytic hydrocracking conditions. The findings suggest that IN718 fouling is primarily governed by the kinetics of sulfidation-induced chemical reactions, whereas W50 fouling is controlled by mass transfer of sulfur-containing species. A phenomenological model is proposed to describe the interplay between the sulfidation mechanism and scale microstructure evolution.