Nanostructured WC-CoCr powder was prepared and deposited on carbon steel substrates by HVOF spraying. The coatings obtained were characterized based on phase constitution, elemental distribution, and microstructure as well as corrosion and sliding wear behaviors. X-ray diffraction was used to identify the main phase constituents and EDS analysis revealed the distribution of Co and Cr in the coating. The mechanisms involved in the formation of microstructure are discussed along with the effects of Cr on coating performance.

In this study, HVOF sprayed NiCr alloy coatings on A213 TP347H boiler steel are evaluated by severe corrosion tests in a high-temperature molten salt environment. XRD and FE-SEM/EDS analysis results are presented and discussed and correlated with corrosion kinetics.

This study assesses the erosion resistance of WC-CoCr coatings produced from multimodal and conventional powders. The feedstocks were sprayed with a high-velocity oxyfuel (HVOF) torch using propane and kerosene as the fuels. Powder morphology and coating structures were analyzed by OM, SEM, and XRD. Coating properties including porosity, hardness, and fracture toughness were measured and erosion resistance was determined by dry sand blasting. The mechanical properties of WC-CoCr coatings deposited using kerosene are shown to be superior to those sprayed with propane. Multimodal WC-CoCr coatings deposited using kerosene had the highest microhardness and fracture toughness, the lowest porosity, and the greatest resistance to solid particle erosion wear.

In this work, process models combining statistics, materials science, and mechanics were developed to optimize and qualify HVOF sprayed coatings as if for aerospace application. In an attempt to correlate process variables with typical coating properties, a preliminary microstructure model was developed using statistical data obtained from 34 design-of-experiments runs. A second model, based on fatigue testing, was also developed. The fatigue model was subsequently used to guide the selection of variables for a final model that is shown to aid in both process qualification and the optimization of process-operating parameters.

In this study, a design of experiment (DOE) approach is used to investigate the influence of powder size and mixing ratio on the microstructure and properties of thermal spray coatings. Nano and micro sized WC-12Co powders combined in different proportions with Inconel 625 were deposited on carbon steel substrates by HVOF spraying. The resulting coatings are examined and the effect of different powder combinations on hardness and yield strength is assessed. Spraying procedures and test methods are described and the findings are discussed. Of the various coatings produced, one shows great promise for wear protection, particularly in oil and gas applications.

In this study, several thermal spray coatings and reference materials were evaluated for potential use in biomass co-fired boilers. The coatings were applied to T92, A263, and X10Cr13 substrates by HVOF and wire-arc spraying using powder (IN625, FeCr, NiCr) and wire (NiCrTi) feedstocks. Coating samples were examined then tested for 5900 h in the superheater area of a fluidized bed boiler burning a mixture of wood, peat, and coal. The corrosion behavior of the coating and reference materials is reported in the paper and the underlying corrosion mechanisms are discussed.

This work assesses the feasibility of using a high-velocity airfuel (HVAF) gun both to grit blast and spray substrate surfaces. A design of experiments (DoE) approach was used to establish relationships between grit blasting variables, substrate surface conditions, and coating properties. Alumina was selected as the abrasive media, the substrates were HSLA steel, and CrC-NiCr and Fe-based powders were used to form the coatings. Uncoated and as-sprayed substrates were characterized based on hardness, residue levels, surface roughness profiles, and adhesion strength, which are correlated with mesh size, feed rate, offset angle, and standoff distance.

With appropriate process control, near-net-shape coatings can be successfully applied to parts with complex geometries using HVOF spraying and fine cermet powders. This study assesses the influence of critical process parameters on the deposition rate and properties of HVOF coatings produced using fine agglomerated WC-12Co powder (2-10 µm) with nanosized WC particles. Spray angle, standoff distance, gun velocity, track pitch, and backside air cooling pressure were varied during the experiments in order to determine their effect on coating hardness, roughness, and porosity as well as deposition efficiency. Variations in spray parameters were found to have a significant effect on deposition rate and coating properties.

The aim of this study is to evaluate the microstructure and corrosion properties of Fe-based coatings produced using different HVAF spray guns. Differences in microstructure, phase composition, porosity, oxide content, and corrosion behavior were observed among the coatings depending on the gun and spraying parameters. The results are presented and discussed in detail.