Tungsten inert gas arc (TIG) process was employed to remelt Fe-based coating deposited by plasma spraying. Subsequently, the microstructure, interface, and the wear resistance of the coatings before and after remelting were studied. The results showed that the lamellar structure, pores, and inclusions of Fe-based coating were eliminated and the porosity significantly decreased from 4% to 0.4%. The as-sprayed coating contained microcrystalline region, nanocrystalline region, and transition region, while single crystal region and rod-shaped (Fe,Cr)₂₃C₆ were observed in the remelted coating. There was no element diffusion and dissolution phenomenon at the interface; thus, the bonding form between the as-sprayed coating and substrate mainly was mechanical bonding. On the contrary, the diffusion transfer belt (DTB) emerged at the interface of the remelted coating and substrate, the remelted coating was bonded with the substrate metallurgically. Additionally, the average microhardness and elastic modulus of the remelted coating increased by 33.4% and 53.2%, respectively, compared with the as-sprayed coating. During wear process, the as-sprayed coating exhibited obvious brittle fracture characteristics, while the remelted coating appeared typical plastic deformation characteristics and its weight loss reduced by 39.5%. Therefore, TIG remelting process significantly improved the microstructure, mechanical properties, and wear resistance of Fe-based coating.

The plasma spray method is widely utilized for enhancing wear, surface fatigue, and corrosion properties through coating. The mechanical and surface characteristics of the resulting coating are contingent upon various spraying parameters, including arc current, working current, spraying distance, and plasma gun traversing speed. This study investigates the impact of these manufacturing parameters on the porosity, hardness, and bond strength of a coating produced from an Al-Ni alloy applied to a Q235 steel substrate. An extensive experimental program was conducted to analyze the influence of these parameters on the coating properties. Consequently, a preferred combination of parameters, identified through a comprehensive evaluation method, yielded greater performance benefits compared to the orthogonal experimental groups.

In order to achieve better knowledge of the thermal barrier coatings (TBCs) by supersonic atmospheric plasma spraying (SAPS) process, an experimental study was carried out to elaborate the physicochemical properties of particles in-flight during the SAPS process. One type of commercially available agglomerated and sintered yttria-stabilized-zirconia (YSZ) powder was injected into the SAPS plasma jet and collected by the shock chilling method. The YSZ particles’ in-flight physicochemical properties during the SAPS process, including melting state, morphology, microstructure, particle size distribution, element composition changes, and phase transformation, have been systematically analyzed. The melting state, morphology, and microstructure of the collected particles were determined by scanning electron microscopy (SEM). The particle size distribution was measured by a laser diffraction particle size analyzer (LDPSA). Element compositions were quantitatively analyzed by an electron probe X-ray microanalyzer (EPMA). Additionally, the X-ray diffraction (XRD) method was used to analyze the phase transformation. The results showed that the original YSZ powder injected into the SAPS plasma jet was quickly heated and melted from the outer layer companied with breakup and collision-coalescence. The outer layer of the collected particles containing roughly hexagonal shaped grains exhibited a surface texture with high sphericity and the inside was dense with a hollow structure. The median particle size had decreased from 45.65 to 42.04 μm. In addition to this, phase transformation took place, and the content of the zirconium (Zr) and yttrium (Y) elements had decreased with the evaporation of ZrO₂ and Y₂O₃.