Abstract Unlike their metal counterparts, composite structures do not readily conduct away the electrical currents generated by lightning strikes. Cost reduction and expected production growth of the next middle range airplanes require automated manufacturing process of polymer components. The development of an automated technology to metallize polymer based composite for lightning strike protection is the aim of the CO3 project (EU Grant agreement: ID831979). In this study, thermal and electrical conductivities of composites were achieved by cold spray deposition of Cu or Al coatings. Critical points to be addressed were substrate erosion during cold spray, lack of polymer-metal adhesion and poor deposition efficiency. Several strategies were tested: i) a thin polymer film was cocured at the substrate surface before cold spraying, to enable implantation of metallic particles in the film, helping coating build-up and protecting the fibers of the composite. ii) Cold spraying a mix of metal and polymer powders to improve coating adhesion and prevent fiber damage. iii) Supercritical Nitrogen Deposition technology, prior to cold spray, to mechanically anchor metallic particles into the polymer. Subsequent cold spraying of purely metallic coatings was more efficient and showed better adhesion. All coatings were tested in terms of adhesion strength and electrical conductivity.

Abstract Cold Gas Spray (CGS) technology has allowed the development of biofunctional composite coatings composed of 45S5 and Polyetheretherketone (PEEK). The combination of a bioactive glass material embedded in a biocompatible polymeric matrix becomes this new composite in an interesting material for orthopedic applications since meet the biomechanical and biological requirements of an artificial implant. In the present study, blends of bioactive glass 45S5 and PEEK powder with different granulometry and 45S5/PEEK ratio have been prepared. These mixtures of powders have been deposited onto PEEK substrates by CGS with the goal of incorporating a bioactive additive to the biocompatible polymer, which can improve the bone-implant interaction of PEEK. The deposition efficiency (DE) and thickness of the coatings have been evaluated and from the results obtained, it was possible to conclude that DE and coating thickness are significantly affected by the granulometry and by the 45S5/PEEK ratio of the blends. By Scanning Electron Microscopy (SEM) inspection, it was observed that the use of blends with high 45S5/PEEK ratio led to the deposition of coatings with high content of 45S5 particles embedded in the polymeric matrix. Finally, the friction behavior of the coatings was analyzed performing ball-on-disk tests and these experiments showed that the presence of glass particles has a beneficial role in the wear resistance of the coatings.

Abstract This paper discusses the development of functional polymer-cermet-matrix composite layers to increase the wear and oxidation resistance of polyimide-based polymer matrix composite layers. It aims to achieve an increase in layer systems made of pure polyimides, which should be similar to the polymer matrix composite substrate matrix up to 100% tungsten carbide cobalt layers and others. The shift systems are examined in a step-by-step and continuous gradation of the reinforcing WC-Co phase. Spray parameter developments for the High Velocity Oxy-Fuel (HVOF) process for coating pure thermosetting polyimide matrix materials as well as various layers of thermosetting polyimides and WC-Co layers on steel and PMR-15 composite surfaces are shown. The results of the HVOF process optimization, the microstructure marking, and the analysis results are displayed. The thermal properties of pure thermosetting polyimide powders and their properties as sprayed layers are compared with differential scanning calorimetry. Paper includes a German-language abstract.

Abstract Hydroxyapatite/polymer composite coatings of different volume ratios were produced using a Plastic Flame Spray (PFS) system. The intent of this processing is to obtain a coating with an optimal combination of biological and mechanical properties of these two materials for skeletal implants. The composite coatings were produced with a mechanical blend of EMMA and hydroxyapatite powder from a fluidized bed powder feeder. Characterization was conducted by scanning electron microscopy on the surface morphology, polished cross-sections and fracture surface morphology of the coatings. The bioactivity of the coatings was evaluated with a calcium ion meter, and the stress-strain behavior was investigated by tensile testing. The biological and mechanical properties were found to be related to the volume and the distribution of the hydroxyapatite in the polymer matrix.

Abstract Polyetherether-ketone (PEEK) and Polyphenylene-sulfide (PPS) are high performance thermoplastics having high heat resistance and high corrosion resistance. Composite powders of PEEK / Alumina (Al 2 O 3 ) with different Al 2 O 3 content have been produced by four processes, which are Mixing (MX) process. Mechanical granulation (MG) process. Melting-crush (MC) process and Heating-granulation (HG) process. PEEK / Al 2 O 3 composite powders have been sprayed with High Velocity Air Fuel (HVAF) spray system. The microstructures of these composite coatings have been evaluated and the properties of these composite coatings have been investigated by the corrosion test, the adhesion test, the ACT-JP test and the abrasive wear test. It was recognized that all the composite coatings containing Al 2 O 3 powder have a good wear resistance. PPS / Al 2 O 3 composite powders have been sprayed with HVAF spray system onto substrate of various pre-heat temperature. It was recognized that the adhesion strength of the composite coatings increases with increasing pre-heat temperature of substrate.

Abstract The high velocity oxy-fuel (HVOF) combustion spray technique has previously been shown to be an excellent solution for depositing crystalline matrix nano-reinforced polymer coatings. The use of multiple scales of reinforcement is expected to improve the load transfer from the larger reinforcing particles to the matrix through the mediation of the smaller particles. The initial step in developing multi-scale coatings is studying the effects of reinforcement size on distribution and properties. Nylon 11 coatings filled with silica particulates of 7 nm, 20 nm, 10µm and 100µm have been produced using the high velocity oxy-fuel (HVOF) combustion spray process. The physical properties and microstructure have been evaluated as a function of the reinforcement size. Nylon 11 was co-milled with the fillers to a 10% volume fraction. The filler was agglomerated at the splat boundaries in the final coating microstructures. All filled coatings had significant changes in x-ray pattern relative to pure nylon 11 coatings, indicative of both increased crystallinity and changes in crystal structure. Coatings containing the smallest reinforcements exhibited improvements of 40 % in scratch and 84 % in wear resistance above those containing the largest reinforcement particles in coatings with nominal 10 vol. % of hydrophobic silica. This increase appeared to be primarily due to filler addition and increased matrix crystallinity.

Abstract For components that are required to function in sliding or rubbing contact with other parts, degradation often occurs through wear due to friction between the two contacting surfaces. Depending on the nature of the materials being used, the addition of water as a lubricant may introduce corrosion and accelerate the degradation process. To improve the performance and increase the life of these components, coatings may be applied to the regions subject to the greatest wear. These coatings may be engineered to provide internal pockets of solid lubricant in order to improve the tribological performance. In the present study, coatings containing a solid lubricant were produced by thermal spraying feedstock powders consisting of a blend of tungsten carbide-metal and a fluorinated ethylene-propylene copolymer-based material. The volume content of this Teflon-based material in the feedstock ranged from 3.5 to 36%. These feedstocks were deposited using a high velocity oxy-fuel system to produce coatings having a level of porosity below 2%. Sliding wear tests in which coated rotors were tested in contact with stationary carbon-graphite disks identified an optimum level of Teflon-based material in the feedstock formulation required to produce coatings exhibiting minimum wear. This optimum level was in the range of 7-17% by volume and depended on the composition of the cermet constituent. Reductions in mass loss for the couples on the order of 50% (an improvement in performance by a factor of approximately two) were obtained for the best-performing compositions, as compared to couples m which the coating contained no solid lubricant.

Abstract This paper evaluates the physical properties of nano-reinforced nylon 11/silicon oxide composite coatings produced using high-speed flame spraying as a function of the process technology and the composition. The coatings were created from nylon 11 powders with starting particle sizes of 30 and 60 micrometer and with 5 to 20% by volume of 9 nm reinforcing silicon oxide particles. Corrosion tests on aluminum and steel substrates showed that the metallic substrate is effectively protected and that the corrosion resistance does not change even if the coating is exposed to salt water for 100 hours. Paper includes a German-language abstract.

Abstract Thermally sprayed coatings made of polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) are becoming increasingly interesting, especially for corrosion protection applications at elevated temperatures in the chemical industry. In contrast to conventional polymers these materials melt at much higher temperatures. Furthermore, PPS and PEEK show enhanced mechanical and chemical stability. Instead of HVOF and plasma spraying, in this paper much simpler and low-cost flame spraying is used because of these advantages. The polymers are investigated along the entire deposition process in order to exclude possible decomposition. Attempts are made with various adhesive layers to reduce the unacceptably high preheat temperatures. The corrosion protection features are examined by means of corrosion tests with various media. The results of the experiments presented in this paper promise coatings of high performance thermoplasts a great future as anticorrosive coatings. Paper includes a German-language abstract.

Abstract This paper describes investigation into the effect of the inorganic fillers on structural and physical-mechanical properties of polyethylene-based composite coatings produced by thermal spraying. A comparative analysis of the thermal spraying methods was carried out using spray polymers as an example. It was found that the powder particles made of aluminum and an Fe-B alloy, which were added to the polymeric materials, act as artificial crosslinking centers. This resulted in a decreasing grain size and an improvement in the physical and mechanical properties of the coatings. At low fill levels of the polymeric materials (up to 10% by volume), the degree of oxidation of the coating material decreased during spraying. Paper includes a German-language abstract.

Abstract A high energy recovery of dc plasma torch has been developed and applied to the deposition of >10 mm thick polymer composites for abrasion resistant protective surfaces. The injection of low cost fillers such as alumina or silica in the hot plasma zone can absorb a lot of energy and cool down the plasma whereas polymer powder is injected downstream in a much cooler zone. Indeed, the energy absorbed by the fillers can then be transferred inside the polymer matrix coating allowing an energy recovery mechanism. The result is a composite polymer/ceramic with the following benefits: The shrinking phenomena due to the polymer recrystallisation is eliminated allowing a good coating adhesion, a high polymer/filler throughput can be achieved and the risk of the in-flight polymer combustion is largely reduced. The fillers addition decreases the overall cost of the coating and the type of filler can influence the composite properties. Abrasion resistant composites have been produced with alumina fillers. Medium density polyethylene (MDPE) sprayed with 45 wt % reinforcement as tested on the modified ASTM G-65 apparatus has shown abrasion resistance as good as ultra high molecular weight polyethylene (UHMWPE), which is one of the highest abrasion resistant polymer. In order to understand the abrasion resistance mechanisms, variables in the coating process such as: size of the fillers, polymer injection angles, polymer degradation and composite microstructure have been analyzed.

Abstract In this study, ethylene methacrylic acid copolymer (EMAA) was used as the matrix to produce EMAA/Al2O3 and EMAA/NiCr composite coatings from dry-blended powder mixtures. This work was conducted to determine processing concerns when using similar sized reinforcement particles of different density in a flame-spray process. This work has utility for applications that require a reduction in mechanical wear and/or to confer upon a polymeric deposit a certain functional property by the introduction of value-added powder. Free-standing coatings were produced to test the mechanical properties of the sprayed deposit. The effects of the filler content on the secant modulus, yield stress, and tensile strength are discussed. The differences in deposition efficiencies among the EMAA, Al2O3, and NiCr are highlighted with respect to particle size and density.