This research aims at introducing new biodegradable/non-biodegradable materials (biopolymers) to the existing Hydroxyapatite (HA)-titanium combination or as a single coating in order to overcome some of the limitations of HA coatings. Biopolymers can act as drug carriers for a localised drug release following implantation; they can also have a structural role by improving the mechanical performance of implants at the bone –implant interface. The proposed materials consisted of biodegradable and non-biodegradable polymers widely used as drug delivery systems: polymethylmethacrylate and polyhydroxybutyrate 98%/ polyhydroxyvalerate 2%. The method used to apply the polymeric powders was oxygen/acetylene flame spraying, due to its superior mechanical advantages over other techniques. Screening tests were used to determine the suitable range of spraying parameters, followed by optimisation to understand of the effects of spraying parameters on coating characteristics (thickness, roughness, adhesion, wettability), in order to obtain an optimal coating design. The polymers were sprayed onto bare titanium substrates. FTIR results showed that the coatings underwent little chemical degradation. Biocompatibility tests showed that cells proliferated well on flame sprayed polymer coatings, which confirms that the coating technique used did not affect the biological performance of the material.

Thermoplastic Polyamide-11 powder coatings serve many industries – such as water handling, automotive, and appliances. This utility is based on the ability to simultaneously provide exceptional resistance to: corrosion, impact/abrasion, and numerous chemicals. Typically application is by traditional methods – electrostatic spray or fluidized bed dipping. The present work demonstrates for the first time that the flame spray method can produce Polyamide- 11 powder coatings very close in performance to those produced by traditional methods. The keys are proper substrate pre-heating, and flame conditions that minimize polymer degradation. Coatings performance, impact resistance, and molecular weight data are presented.

The significance of biofuels and the other chlorine-containing fuels in energy production is in strong increase. Serious erosion-corrosion problems in boilers combusting fuels with high chlorine-content have been detected frequently. A series of erosion-corrosion and corrosion tests were performed on thermal sprayed coatings and coating precursors in chlorine-containing environments in order to evaluate possibilities to utilize thermal sprayed coatings for erosion-corrosion protection in boilers combusting chlorine-containing fuels. A series of hot erosion and erosion-corrosion tests were performed on thermal sprayed coatings at elevated temperatures with and without chlorine. Carbide-containing HVOF coatings performed well in hot erosion tests, but they were completely destroyed in the presence of chlorine due to rapid oxidation of carbides. Metallic HVOF coatings with high chromium content performed well in both conditions. Iron-based arc-sprayed coatings with unhomogeneous microstructure suffered more hot erosion and erosion-corrosion damages than metallic HVOF coatings. The E-C (erosion-corrosion) resistance of carbide-containing coatings in the presence of chlorides was worse than expected. A series of oxidation tests were performed on various carbides in order to elucidate the effect of chlorine on high temperature oxidation behavior of carbides. TGA and isothermal oxidation tests proved that gaseous chlorine-containing species and also solid chlorides have a detrimental effect on oxidation resistance of tested carbides.

In this study, polyamide 11 and polyamide-alumina layers are produced by flame spraying and assessed based on microstructure and corrosion and wear resistance. Among the more notable findings: During the spraying process, there is a loss of crystallinity and polymorphism in the polymer due to high heating and cooling rates. Although some particle degradation occurs in flight, it is does not significantly alter the properties of the polymer. Insufficient substrate temperature impedes the melting of the polymer matrix and embedding of the ceramic filler particles, which has a negative effect on the abrasive wear resistance of the resulting composite layer. Overall, the coatings exhibit good corrosion resistance. During electrochemical testing in a saline solution, there was no electrolyte penetration. Paper includes a German-language abstract.

A new thermal spray technology has been proposed. Called Electrical Chemical Thermal Spray (ETCS), it combines plasma energy with the combustion gases of solid propellants to heat and accelerate particulate materials. The hybrid technology promises new degrees of freedom in materials processing over the conventional thermal spray processes by allowing thermal energy transfer to the particles and particle accelerations to be optimized separately. Experimental coatings were formed using a prototype system made from a converted ½” plasma gun fueled with double-base solid propellants to explore this novel concept. The prototype test-facility equipment was limited to single-shot mode. Examination of the coatings formed, and conceptual analysis by analogy to conventional technologies was used to assess the capabilities and limitations of the hybrid process. Impressive in-flight powder velocities of 1100 m/s were reached, with deposition yield efficiencies of 60 - 85% achieved for WC-Co coatings after first round of optimization. However despite the ability to deposit single-shot carbide and metallic coatings with thickness exceeding 200 µm. chemical degradation and extensive cracking combined to limit attractiveness of coatings as compared to those produced using commercial technologies. Unlike the oxidation effects with atmospheric plasma spray and the various low-velocity flame-spraying technologies, chemical degradation in the prototype ETCS was the result of interaction between the gases produced from the combustion of the propellant and the coating material. It is seen that the organic, nitrocellulose based solid propellants are inherently unsuitable for spraying reactive material. With suitable fuels however, it is believed that the inherent advantages of high throughput, versatility and low labour requirements are such that ETCS will have commercial advantages for the coating of large structures.