This paper presents the results of two metals coatings, molybdenum and tantalum, prepared by Controlled Atmosphere Plasma Spray (CAPS) onto Al 6061 substrates that were thermal cycled to calculate the effective coating modulus. Traditional uniaxial tensile testing samples were prepared from thicker duplicate coatings for comparison, as well as to measure thermal expansion properties and oxygen and nitrogen content. The molybdenum samples cut from thicker coatings were un-able to be tensile tested due to their fragility. Thermal cycle testing of molybdenum on an Al 6061 substrate was found to have a modulus approximately 18 to 19% of literature values for bulk molybdenum using the bi-layer beam thermal cycling method. Additionally, non-linear modulus behaviour was observed in the molybdenum sample when enough thermal strain was induced to shift the coating from a compressive to tensile stress state. The tantalum coating was found to have a modulus approximately 42 to 46% of literature values for bulk tantalum using the bi-layer thermal cycling method. Traditional tensile testing measured a modulus approximately 44 to 46% of bulk, which shows good agreement between the two methods and supports that the bi-layer thermal cycling method is valid for plasma sprayed refractory metal coatings.

Acquisition of a new LVPS and APS coating system at Delta Air Lines necessitated optimization of the coating parameters on both systems, especially for application of bond coat (LVPS) and top coat (APS) for a TBC coating system. To expedite the coating optimization, it was determined that a design of experiments (DOE) approach would best enable the establishment of the operating window for the two systems. Samples prepared were primarily evaluated for their performance while exposed to a cyclic oxidation cycle. Samples were also evaluated for the microstructure and composition using energy dispersive spectroscopy (EDS) analysis. Samples from the ceramic coating DOE were also evaluated for their erosion characteristics. Results indicate a low correlation between the individual bond coat parameters evaluated to the furnace cycle life. However, the top coat spray parameters were found to have a greater correlation to furnace cycle life and erosion performance.

Tungsten heavy alloy (WHA) of W-Ni composition was deposited from a blend of standard thermal spray powders using a radio frequency inductively coupled plasma torch in a protective atmosphere. The coating contained a fully developed WHA structure, i.e., spherical W particles embedded in a Ni-rich matrix. Bending tensile strength R m , bending yield strength R p,0.2 , and elastic modulus were measured and compared with W-Ni-Co references fabricated by sintered and quenched (SQ) and forged and annealed (FA) powder metallurgy (PM) processes. The fatigue and fracture properties of the plasma spray deposits are comparable with those of the SQ-PM reference material, but inferior to those of the FA-PM reference. The results of various property tests are presented and analyzed in the paper.

Three different coatings were deposited using the Detonation Gun Spraying (DGS) technology from steel powders alone, and steel powers mixed with Fe3C and SiC particles, respectively. The microstructural characteristics of these coatings were examined and the hardness of each type of coating was studied. The morphology and structure of the feedstock powders were affected by the exposure to high temperature during the spraying process and rapid solidification of steel powders that resulted in the formation of an amorphous structure. The unreinforced steel coating had the highest hardness among the three types of coatings, possibly due to a higher degree of amorphization in the coating compared to the other two samples. The microstructural observation confirmed the formation of dense coatings with a layered structure with good connectivity between layers with minimum defects and porosities in the interfacial regions.

Cold gas spraying is a solid-state deposition process developed for metallic powders as feedstock materials. For ceramic materials; such low temperature-high velocity kinetic process is still questionable but could have interesting advantages. In the CERASOL project (ANR-19-CE08-0009); the nature and the architecture of porous ceramic powders involving agglomerated sub-micrometric grains are investigated. To that purpose; three oxide ceramics powders (alumina; zirconia and yttria) have been prepared for cold spray. These powders were analyzed in order to assess their architecture (composition; particle size; porosity; density; crystallite sizes…). Preliminary cold spray experiments were carried out implementing velocities measurements for various stand-off distances and spraying of coupons with line experiments. The characteristics of the deposited layers have been examined by SEM and XRD in order to discuss the role of the powder architecture on the impact behavior of the nanostructured agglomerated particles. The role of the gas stream that affects the kinetic and the trajectory of the particles are also discussed.

Thermal spray coatings are widely used to protect materials from corrosion, wear, and oxidation, but they have yet to reach their full potential because of porosity limitations and the detrimental effects of oxidation on interlamellar bonding. This paper investigates an atmospheric plasma spraying process that deposits oxide-free dense metallic coatings with well bonded lamellae. The process produces ultrahigh temperature metallic droplets, up to 2650 °C, using specially designed powders that are deoxidized in-flight through the evaporation or gasification of oxides. The impact of these oxide-free ultrahigh temperature droplets has a spreading-fusing, self-metallurgical bonding effect resulting in fully dense bulk-like metallic coatings. Various coating materials, including NiCrMo, 304SS-Mo, NiCrBSi, and Al, are investigated, demonstrating the versatility of the new technique.

Microstructure and physicochemical properties of a thermally sprayed coating depend on the dynamics of the particles interacting with the spray jet. This is especially the case for electrical properties. In this study, different spraying processes were used to spray p-type and n-type half-Heusler powders. Thermoelectric powders, Hf20Zr75Ti05CoSb80Sn20 (p-type) and Hf60Zr40NiSn98Sb02 (n-type), were selected due to their interesting electrical properties. The spray processes were evaluated based on coating composition and mechanical property measurements. The only coatings of practical interest were those that were plasma sprayed and they were examined in detail to assess the effect of process parameters on coating properties.

In subzero conditions, atmospheric ice naturally accretes on surfaces in outdoor environments. This accretion can compromise the operational performance of several industrial applications, such as wind turbines, power lines, aviation, and maritime transport. To effectively prevent icing problems, the development of durable icephobic coating solutions is strongly needed. Here, the durability of lubricated icephobic coatings was studied under repeated icing/deicing cycles. Lubricated coatings were produced in one-step by flame spraying with hybrid feedstock injection. The coating icephobicity was investigated by accreting ice from supercooled microdroplets using an icing wind tunnel. The ice adhesion strength was evaluated by a centrifugal ice adhesion tester. The icing performance was investigated over four icing/deicing cycles. Surface properties of coatings, such as morphology, topography, chemical composition and wettability, were analyzed before and after the cycles. The results showed an increase in ice adhesion over the cycles, while a stable icephobic behaviour was retained for one selected coating. Moreover, consecutive ice detachment caused a surface roughness increase. This promotes the formation of mechanical interlocking with ice, thus justifying the increased ice adhesion. Finally, the coating hydrophobicity mainly decreased as a consequence of the damaged surface topography. In summary, lubricated coatings retained a good icephobic level after the cycles, thus demonstrating their potential for icephobic applications.

Thermally sprayed WC-Co coatings provide excellent wear resistance and corrosion protection under heavy loads, but their application usually involves additional grinding and polishing steps, which can be 3-4 times costlier than the spraying process itself. There is thus the motivation to develop a process that produces smooth, near-net-shape carbide coatings. This contribution is an investigation of WC-12Co coatings obtained by suspension HVOF spraying. Significant work was devoted to the development and characterization of water-based hardmetal suspensions synthesized from commercially available WC and Co powders. The suspensions produced were sprayed using the HVOF process, and the resulting coatings were evaluated based on microstructure, hardness, and phase composition.

This study investigates the effect of composition on the antibacterial and antiviral properties of hydroxyapatite/titania composite coatings deposited by suspension plasma spraying. Hydroxyapatite is a bioceramic material used as a plasma-sprayed coating to promote osseointegration of femoral stems. TiO2 has promising photocatalytic activity and good efficiency in destroying bacteria, viral species, and parasites. Prior to coating, substrates were grit blasted, ultrasonically cleaned, and heated to enhance adhesion strength. The microstructure of the resulting coatings was then characterized using XRD and Raman spectroscopy. Test results indicated that SPS transformed Ti2O3 into TiO2 with mixed phases. Ti4O7 and Ti3O5 phases were also identified, which show photocatalytic activity due to oxygen vacancies. Antibacterial and antiviral tests were conducted as well.

Grinding wheels are usually manufactured by powder metallurgical processes, i.e. by moulding and sintering. Since this requires the production of special moulds and the sintering is typically carried out in a continuous furnace, this process is time-consuming and cost-intensive. Therefore, it is only worthwhile for medium and large batches. Another influencing factor of the powder metallurgical process route is the high thermal load during the sintering process. Due to their high thermal sensitivity, superabrasives such as diamond or cubic boron nitride are very difficult to process in this way. In this study, a novel and innovative approach is presented, in which superabrasive grinding wheels are manufactured by thermal spraying. For this purpose, flat samples as well as a grinding wheel body were coated by low-pressure (LP) cold gas spraying with a blend of a commercial Cu-Al2O3 cold gas spraying powder and nickel-coated diamonds (8-12 μm). The coatings were examined metallographically in terms of their composition. Afterwards, the grinding wheel was conditioned for the grinding application and the topography was evaluated. This novel process route offers great flexibility in the combination of binder and hard material as well as a costeffective single-part and small-batch production.

Plasma spraying was used to deposit Li3PO4 coatings from sintered dense powders in three size ranges to study the effects of particle size and spraying distance. Coating microstructure, crystal structure, and composition were characterized using SEM, XRD, ICP-MS, and FTIR. It was found that sintered dense powders have a high temperature orthorhombic phase (γ-Li3PO4) that differs from the β-Li3PO4 phase associated with agglomerated Li3PO4. Plasma-sprayed coatings produced from these powders have similarly dense microstructures with fracture-surface morphology like that of sintered bulk. The effect of particle size and spraying distance on atomic ratio is also investigated in the study.

In this work, CeO 2 -G d2 O 3 co-stabilized ZrO 2 (CGZ) thermal barrier coatings are deposited by solution precursor plasma spraying and the microstructure, phase stability, thermophysical properties, and thermal cycling behaviors of the resulting coatings are investigated and discussed in comparison to conventional 8YSZ coatings.

This study investigates the effect of deposition temperature and particle size on lanthanum strontium chromite (LSC) deposits produced by atmospheric plasma spraying. The results show that dense deposits with lamellar interface bonding can be achieved at temperatures above the critical bonding temperature and that particle size has a significant effect on chromium vaporization losses. The loss of chromium may be responsible for the low electrical conductivity of LSC deposits produced from small powders, which suggests that conductivity can be controlled with appropriate process adjustments.

In this work, silicon carbide coatings were fabricated by plasma spray-vapor deposition in order to study the effect of plasma gas mixtures on coating microstructure and phase composition. Coatings deposited by Ar-H 2 plasma gas were found to contain a composite phase of SiC and Si. Moreover, the content of Si increased with increasing H 2 content in the gas. The deposition of Si is possibly due to the reaction of C and hydrogen species in the plasma jet, which would explain why pure SiC coatings were obtained when Ar-N 2 gas was used.

This study investigates the co-deposition of aluminum and chromium oxides from solution precursor feedstocks with the aim of maximizing the α-alumina content. A hybrid water-stabilized plasma torch was used to spray the feedstock materials and the deposition principles were studied. The chemical composition of the deposits corresponded to the formulation of the feedstocks, indicating a uniform deposition of both materials. It was found that α-phase content can be increased in the coatings by increasing the Cr-forming precursor in the solution.

This study assesses the effect of different alloying elements on the microstructure, oxygen content, hardness, and corrosion resistance of stainless steel coatings produced by atmospheric plasma spraying. SUS836L stainless steel powder with Si, Mn, and B additions served as the base feedstock alloy to which different amounts of B, C, Mo, Ti, Nb, V, and Cu were added. The powder mixtures were sprayed on carbon steel substrates and the deposits were examined and tested. The results show that B and C additions of 2-3% have a beneficial effect, but at 5% cause a drop in corrosion resistance that proved to be remediable through the addition of Cu, which improves the corrosion potential of the matrix phase by its combined action with Mo, Si, and B. The effect of Ti, Nb, and V, which are added to suppress Cr oxidation in molten alloy particles during flight, is that it promotes that formation of fine carbide and boride compounds, increasing hardness without sacrificing corrosion resistance. In addition to these findings, the study also shows that the coatings developed are in many ways comparable to Ni-based self-fluxing alloy coatings.

This study compares the microstructure of Al 2 O 3 coatings produced by detonation gun spraying (DGS) and laser stereolithography (SLA). The SLA samples mostly consisted of alumina and voids, while the DGS-deposited alumina contained additional features such as splats, pores, cracks, and boundaries. DGS deposits were also denser with about 3% porosity compared to 8% porosity in the SLA samples. EDS analysis showed that both coatings contained only aluminum and oxygen, although additional carbon was detected in the SLA samples, indicating the presence of residual binder (resin based) material. XRD analysis revealed a mixture of α and γ-Al 2 O 3 phases in the DGS coatings, but no phase change in the SLA samples.

In this study, dicalcium silicate (Ca 2 SiO 4 ) coatings were deposited on stainless steel substrates by atmospheric plasma spraying. Salt spray and immersion tests were carried out to evaluate corrosion performance and XRD, SEM, and EDS were used to analyze phase composition and microstructure. During corrosion testing, calcium carbonate crystals appeared on coating surfaces and the pores were filled with hydration products, producing denser coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy plots indicated that the corrosion resistance of the coatings increased after immersion in saltwater and artificial seawater, and in the latter case, a silica-rich layer was observed between the coating and the calcium carbonate crystals.

This study shows how data-driven modeling tools aid in the development of alloys that meet specific processing, property, and performance requirements. By leveraging a “big data” approach, two new alloys were designed that outperform commonly used materials in hardfacing and wear plate overlay applications. Over one million alloy compositions were analyzed to find two with the right combination of matrix and hard phases to provide the desired level of impact and abrasion resistance. The difference between the two alloys is in their matrix phase; one being austenitic, which has higher toughness, the other being martensitic, which has higher resistance to abrasive wear.