Despite their light weight, 2.3 times lighter than Al, polymers are limited to application with low thermal, wear, and abrasion demands. The enhancement of the functional surfaces of the polymers using thermal spraying techniques is a challenging task due to the thermal degradation of polymers, the low wettability, and the disparate atomic properties. The twin-wire arc spraying (TWAS) process comprises two contradictory features. Almost all spraying particles are in a molten state on the one hand, and on the other hand, the spray plume has the lowest heat output among the different thermal spraying techniques. Therefore, it is a promising spraying technique for the required surface improvement. The surface of the 3D-printed parts was metalized using two successive layers. The first layer is a TWAS coating made of low-melting ZnAl 4 to avoid thermal degradation and provide a bond coat. The topcoat is also applied using a TWAS process and was made out of Ni-WC-Co as cored wires. The top hard coating has improved the wear resistance of the polymers by 14.6 times. The erosion of the coated and uncoated specimens was determined using a low-pressure cold gas spray gun. Ni-WC-Co coating led to more than five times higher erosion resistance.

Coatings of poly(ether-ether-ketone) (PEEK) have been produced using the high-velocity air fuel (HVAF) thermal spray technique. These coatings have been produced at 50 and 100 mm nozzle lengths and 200, 300, and 400 mm gun-to-substrate distances on stainless steel 304 substrates. The techniques used to characterize and determine the extent of thermal degradation of the PEEK coatings were valence-band XPS and FTIR-ATR. Valence-band XPS showed that, in general, minimal degradation of the PEEK occurred during the HVAF thermal spraying process. FTIR-ATR results showed that more surface degradation of the PEEK coating occurred at the 200 mm gun-to-substrate distance for both nozzle lengths than at the larger gun-to-substrate distances. Specifically, absorption bands appeared at 2918 and 2850 cm -1 , which correspond to alkane –CH 2 – asymmetric stretching modes. The resolution of the 672 cm -1 peak, which corresponds to C–H vibrations on the phenyl ring, increased from one to two peaks in the spectra of the 200 and 300 mm gun-to-substrate runs. This indicates a structural change in the phenyl ring, possibly indicating a change in the extent of crystallization of the PEEK polymer.

Glazes are attractive materials as they can be applied onto metallic or ceramic substrates to confer on them specific properties. They find numerous applications, from art ornamenting to protection against corrosion. Conventional process (vitreous glazing) requires a high temperature treatment (up to 1400 °C in some cases) to fuse glazes after their application on the surface to be covered. This treatment cannot be hence applied onto heat-sensitive substrates without severe degradation. Previous studies showed that manufacturing glaze layers by flame spraying prevents the substrate from thermal degradation. The coating formation mechanisms are different from the ones encountered with crystallized ceramic materials: the high surface tension of glazes prevents the particles from being totally spread (i.e., "dewetting" phenomena). Effects of glaze powder characteristics (chemical composition, particles morphology) on coatings structures were also studied. Furthermore, chemical analyses proved that flame spraying did not modify glaze compositions. The most adapted powder to flame spraying has been hence selected. This contribution describes the coating formation mechanism and discusses the influence of the feedstock powder physical properties on coating characteristics. It also estimates effects of spraying parameters on coatings morphology.

Numerical predictions and experimental observations have been correlated to improve the qualitative understanding of the degree of thermal degradation occurring during the HVOF spray deposition of Nylon-11. Particle residence time (<1 ms) in the HVOF jet was insufficient for significant decomposition of the Nylon-11 but was sufficient for noticeable discoloration (yellowing) of the particles of a powder with a mean particle size of 30 µm. Experimental observations showed this to be the case even though numerical predictions indicated that the temperature of a 30 µm diameter particle should be considerably higher than the upper degradation limit of Nylon-11. Initial thermal oxidation of Nylon-11 promotes the formation of carbon-carbon double bonds that strongly absorb in the visible spectrum even at concentrations of parts per million, resulting in discoloration of the Nylon.

The unique wear protection properties of tungsten carbide metal matrix composite materials are resulting in their increasing use in the oilsand industry to combat severe low stress sliding abrasion and various types of slurry abrasion and erosion. Their successful application, mainly in bulk welding and spray coating forms, has extended component service lives, improved reliability and reduced maintenance costs. Increased use of tungsten carbide metal matrix composite hardfacing deposits in oil sands applications is the direct result of understanding carbide thermal degradation and the processes used to deposit these materials. Plasma transferred arc welding (PTAW) has proven to be an effective process for applying these materials. Current and future work on PTAW and other candidate processes to establish the optimum carbide hardfacing method will be reviewed.

Most metallic and ceramic splats exhibit temperature-dependent behavior when they strike a metal substrate and assume a shape that suggests temperature-dependent wetting properties. In this study, the authors investigate the relationship between high-temperature oxidation, substrate morphology, and the flattening behavior of free-falling droplets. Substrate surfaces are examined by means of atomic force microscopy, which shows that changes in morphology of just a few nanometers can have an effect on flattening behavior. Paper includes a German-language abstract.