In this study, the in-situ corrosion behavior of an Fe-based amorphous coating is investigated in a simulated deep sea environment (80 atm). FeMoCrYCB powder produced by gas atomization was deposited on 316L stainless steel substrates by HVOF spraying. The amorphous iron coatings exhibited greater pitting resistance than stainless steel under high hydrostatic pressures, evidenced by higher pitting potential, longer pitting incubation time, and reduced pitting growth. Passive films that formed on the amorphous coatings were also analyzed and found to be thicker, more uniform, and harder than those that developed on 316L stainless steel, indicating that the former are more difficult to break down and more resistant to Cl- ion penetration.

This paper investigated the role of particle injection on inflight particle behavior and its coupling effect on plasma plume in an external orthogonally injected air plasma spray system as well as effects of primary, secondary and carrier gases on in-flight particle status through both experiments and simulations. Diagnostic sensors such as In-flight Particle Pyrometer (IPP) and Spray Position Trajectory (SPT) have been used to obtain the plume characteristics and ensemble temperature, while DPV-2000 was used to measure the distributions of individual particle status such as temperature, velocity and size at the maximum particle flux point. Three-dimensional simulations have been carried out for the corresponding experimental conditions to examine the effects of in-flight particle heating on the plasma plume and in-flight characteristics at different spray distances. Both experiment and simulation results show that particle temperature and velocity will initially increase with plume angle and then decrease after reaching a maximum value for different combination of process parameters at the same plume angle. Theoretical analysis shows strong dependence of the plume angle on the velocity ratio of vertical component from the carrier gas to the horizontal one from primary and secondary gas at their respective nozzle exits. This study enables a better understanding of influence of plasma forming and stabilizing parameters on the particle in-flight characteristics.

There have been recent efforts to expand the thermal spraying capabilities for novel corrosion resistant coatings for metal bipolar plates were produced by thermal spraying for proton exchange membrane (PEM) fuel cell applications. Recently, substrate heated by plasma gun or by external laser beam has been proposed to enhance the mechanical and thermal properties of the coatings. Studies were found that with sufficient substrate heating, substrate melting may happen. When droplets solidified on a thin liquid layer on the top of the substrate, conditions will be similar to crystal growth and Epitaxy film growth will be possible. It is therefore possible that using substrate melting as tool to promote epi-layer growth using plasma spraying. Difficulty is how to control the substrate temperature to cause substrate melting during droplet solidification. In this study we will propose a new idea for better temperature control on the substrate. The capability of epitaxy growth using thermal spraying will be investigated. Molybdenum droplets impact on an Aluminum substrate will be studied. A splat formation model including undercooling, nucleation, and non-equilibrium solidification will be used to study the possibility of the substrate melting and grain size distribution.

Fe-Al based composite coatings were deposited on Grade 20 steel substrates by High Velocity Arc Spraying (HVAS) technology. Hot salt corrosion properties of the coatings were studied at the temperatures of 450 °C,650 °C and 800 °C . Results showed that the corrosion resistance of the Fe- Al/Cr 3 C 2 composite coatings changed little with the increase of temperature, contrasted to the substrate and Fe-Al coatings. The excellent corrosion resistance of the Fe-Al/Cr 3 C 2 composite coatings was attributed to the oxidation of the iron, aluminum and chromium to form protective scales. In hot salt, there are mainly iron oxides at the outer corrosion surface; aluminum and chromium oxides are found at the inner corrosion surface, which can effectively protect the Fe- Al/Cr 3 C 2 composite coatings from corrosion.