Jiri Matejicek

The 2016 Thermal Spray Roadmap

Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications.

Elastic and Anelastic Behavior of TBCs Sprayed at High-Deposition Rates

Coatings sprayed at high-deposition rates often result in stiff, dense, and highly stressed coatings. The high deposition temperature at which the coatings are formed is responsible for these characteristics. In this paper, TBCs were sprayed at high-deposition rates, increasing the tensile quenching stresses beyond the threshold of crack opening during spraying. Dense structures were observed within a pass, in the presence of micro and macro defects specifically horizontal cracks within interpasses and vertical segmentation cracks. Mechanical properties, mainly the elastic and anelastic behavior of TBCs were significantly affected by the strain accommodation and friction occurring within intersplats and interpass interfaces. The strain tolerance obtained in as-sprayed conditions decreased as the microstructure and defects sintered during high-temperature heat cycles. The non-linearity degree decreased while the elastic modulus of the various coatings increased to a maximum value.

Resuts of interaction of XUV laser pulses of nanosecond duration with difficult-ablated-materials

Summary form only given. It is well known that each photon of extreme ultraviolet (XUV) radiation carries energy higher than 20 eV, what is more than any binding energy in a solid state. Provided that energy of these photons is deposited in some localized volume (for example in a surface layer - which is true for XUV and soft X-rays) a non-thermal melting can appear1. This contribution presents experimental results of interaction of focused pulsed XUV laser (λ ~ 47 nm/ ~1.5 ns/150-350 μJ) radiation with tungsten (W), molybdenum (Mo), and silicon carbide (SiC) - three materials considered as perspective armour for plasma facing components in future thermonuclear reactors. It was found that W and Mo behave similarly: during the first shot the laser footprint is covered by melted and re-solidified material, in which circular holes appear - residua of just opened pores, from which explosively escaped pressurized (up to atmospheric pressure) air. The W has tendency to peel off its surface layer: semidetached chip is then more intensely heated (due to locally reduced thermal conductivity) and rounded. The SiC has negligible porosity, and at melting point it de-composes to elements; therefore, the crater morphology can be related to local laser-energy-density above ablation threshold. When more shots are superimposed, in all three investigated materials the crater depth remarkably increases up to ~10 accumulated shots, between 10 and 20 accumulated shots this increase is slowed down, and above 20 it is very small.