Atmospheric plasma sprayed (APS) CuNiIn coatings have been widely used for fretting wear protection in many important areas such as aircraft engines for decades. The oxides in CuNiIn coating prepared by APS hinder splat bonding formation and thus degrade the coating fretting performance. In this study, CuNiIn powders of different boron contents were designed to realize the self-oxide-cleaning effect for in-flight molten droplets and thus deposit the dense CuNiIn coating with high fretting performance. Scanning electron microscope was used to characterize the microstructure. The oxygen content in the coating was measured by the inert gas fusion technique. Fretting test was performed for three coatings under different loadings. The results show that CuNiIn2B and CuNiIn4B coatings presented the oxide content of 0.40wt% and 0.38wt%, which are lower than 1.6wt% of the CuNiIn coating. The oxygen content in the CuNiIn4B coating decreased with the increase of spray distance while the oxygen content in CuNiIn coating increased with the increase of the spray distance. Such results clearly reveal the boron in-situ deoxidizing effect of inflight molten droplets. As a result, the dense CuNiIn2B and CuNiIn4B coatings were deposited with oxide-free molten droplets. The test results showed that the fretting wear performance of B-alloyed CuNiIn coatings were increased by a factor over three comparing with conventional CuNiIn coating.

Since the plasma sprayed coatings always present a limited interlamellar bonding, it is difficult for a plasma sprayed coating to be applied in corrosion environment without any post-spray treatment. In this study, a NiCr powder alloyed with boron was employed to fabricate fully dense corrosionresistant coating by plasma spraying through in-situ deoxidation effect of boron. As reported previously, plasma sprayed Ni 20 Cr 4 B coating presents fully dense microstructure with few isolated pores. Due to the oxide-free state of the inflight particles by the deoxidation effect of boron, the splats were effectively bonded upon impact so that the inter-splat boundaries were indiscernible. A long-term immersion corrosion test in NaCl solution was conducted for 80 days to confirm that the plasma sprayed Ni 20 Cr 4 B coating presents the superior resistance against the corrosion, which was comparable to the flame spray-fused NiCrBSi coating. Furthermore, the cross-sectional microstructure of the Ni 20 Cr 4 B coated Al alloy samples after 80 days immersion revealed that the plasma sprayed Ni 20 Cr 4 B coating was dense enough to completely block the penetration of corrosive substance in such an aqueous corrosion environment.

High-velocity oxyfuel (HVOF) sprayed coatings of Cr3C2-NiCr containing solid lubricants such as nickel cladded graphite and hexagonal boron nitride were successfully developed and characterised with the aim of optimizing their friction and wear behaviour. HVOF technology was used for the integration of solid lubricants to achieve strong cohesion between particles while minimizing thermal decomposition. Coating microstructure and composition were measured and correlated to the results of tribological and corrosion tests. The integration of the solid lubricant greatly reduced friction and wear volume at room temperature, but the lubricating effect was highly dependent on atmosphere and temperature. Cr3C2-NiCr with hBN, however, tends to exhibit more stable wear resistance over a wider temperature range and can be used at temperatures beyond 450 °C.

The effect of deposition pressure on the microstructure and ablation behavior of ZrB2 coatings deposited by very low pressure plasma spraying is investigated. The results show that under a chamber pressure less than 50 kPa, as the spray chamber pressure decreases, the porosity of the coating deposited at the same distance decreases, and the coating prepared under 100 Pa presents the lowest porosity of 1.79 %. Furthermore, among the ZrB2 coatings deposited at 100 Pa, 5 kPa, 10 kPa and 50 kPa, the dense coating deposited at 100 Pa showed the lowest ablation rate of 0.33 μm/s, 0.75±0.08 mg/s.

Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes for applying protective coatings to components used in waste incineration plants. This paper discusses the development of relatively low-cost Fe-Cr-Si coating materials for incinerator applications and the corrosion and wear properties that have been achieved using conventional arc spraying methods.

Neutron absorbers are expected to play an important role in the long-term storage of spent nuclear fuels and nuclear wastes. High neutron absorbing capability, long-term stability, and the capacity to stay with the fuel are important criteria in preventing critical conditions during possible waste package degradation in geological time frames. Existing available neutron absorbing materials are based on boron or boron-10 isotope modifications of austenitic stainless steels or to aluminum based metal matrix composites. Specific rare earths such as gadolinium, samarium, or europium are found to have much higher thermal neutron cross section than boron or boron-10 but have high reactivity which limit their stability and ultimate applicability. In this paper, it is described how it is possible through a nanotechnology approach, to overcome the solubility and stability limitations of conventional materials to allow incorporation of high amounts of boron and rare earths into advanced HVOF coatings. During the development of the NeutraShieldTM Coatings, it was found that high fractions of rare earth elements such as gadolinium along with high concentrations of boron could be dissolved in the liquid melt and then remain soluble in the metallic glass structure. During the transformation of the glass to the nanocomposite structure, the rare earths are found to come out of supersaturated solid solution to form stable nanoscale ternary intermetallic R2Fe14B phases which form in a commensurate fashion and is protected by the highly noble matrix. Abstract only; no full-text paper available.

This paper presents the results an experimental study on ferroalloy-base flux-cored wire coatings. The work conducted shows that it is possible to improve the structure and properties of coatings by adding aluminum to the ferrochromium powder charge and rare-earth elements and calcium to ferroboron. This reduces the oxygen content and porosity of coatings by a factor of 1.5-2. It also reduces residual tensile stresses in outer coating layers and improves coating-substrate adhesion strength as well as abrasive wear resistance.