Yttria partially stabilized zirconia (YSZ) was atmosphere plasma sprayed on to mild steel substrates. The spray parameters were varied to determine their effects on the elastic modulus of the coating. The parameters were (i) continuous spray vs. paused spray, (ii) bond coat vs. no bond coat, and (iii) cooled vs. not-cooled. The elastic modulus was measured using laser ultrasonics and Knoop Indentation. Using indentation, the continuous/ paused spray exhibited the greatest effect with the paused spray samples having a lower elastic modulus value regardless of the condition of the other parameters. The other parameters did not reveal any statistically significant effect. The laser ultrasonics measurements showed that cooling and no-cooling had a greater effect on elastic modulus, with the other parameters having little effect. Laser ultrasonics detected parameters whose influence can be detected near the surface (in this work the cooling and no-cooling), but did not detect those parameters that influence the properties throughout the coating. Indentation detected the parameters that influence the properties throughout the coating, in this work continuous and paused spraying.

Thermal barrier coatings have been extensively used in several industrial segments. The material used as an insulator in such systems has been partially stabilized zirconia (PSZ) plasma sprayed over a metallic bond coat layer. The ceramic layer is usually porous, thus improving insulation properties. The porosity also increases gas permeability and, therefore, reduces oxidation resistance of the coating. Post-treatments have been applied to reduce the open porosity and improve oxidation resistance. In this work thermal barrier coatings were applied on low carbon steel substrates using two sets of bond coat, i.e., metallic and metal-ceramic. The metallic bond coat was NiCrAlY. The metal-ceramic bond coat was a mixture of NiCrAlY and 8% yttria partially stabilized zirconia, which were applied by simultaneous feeding to the plasma torch from two powder feeders. A sol-gel method was employed to impregnate the porous ceramic top coat with alumina or zirconia. The samples in the as-sprayed and post-treated condition were characterized using mercury intrusion porosimetry (MIP), thermal conductivity. KEY WORDS: Thermal Conductivity, TBCs, Sol-Gel.

Experimental designs have been used by the thermal spray community to improve and optimize spray parameters to produce coatings with desired properties. The influence of four spray parameters including top and bond coat thicknesses, substrate temperature, and spray distance on the mechanical properties of plasma sprayed thermal barrier coatings has been examined. Two experimental matrices; (i) a four by nine according to a Taguchi experimental design, and (ii) a four by seventeen according to a full factorial design of the experiment, were developed. Six samples from each group were tested using a four point bend arrangement. Yield strength and elastic modulus were calculated from the four point bend test. A multi-linear regression analysis on yield strength and elastic modulus values from each experimental matrix was carried out to determine the influence of each spray parameter on these properties. The multi-linear regression analysis results for these two experimental matrixes are compared.

In this paper, the processes as well as the first results regarding the economic efficiency and plasma fuel properties of nanostructured zirconium oxide powder particles are explained. The paper evaluates values for porosity, hardness, roughness, and crystallite size. In addition, both the morphology of the powder particles and the spatter are analyzed by SEM, and cross sections of the coatings are observed using optical microscopy. These results are compared to coatings made from a commercially available yttria stabilized zirconia powder. Paper includes a German-language abstract.

This paper investigates the effect of HVOF thermally sprayed WC-Co coatings on the cyclic deformation of the aluminum alloy 2024-T4 and the steel SAE 12L14. Strain gages are glued on the specimen surface to measure the strain response after certain intervals of fatigue cycles. The strain is also measured during the fatigue test. A calibrated beam is used to apply the bending moment and the stress calculated using the flexural formula. The stress-strain curves for uncycled and cycled specimens are determined. The dynamic strains for the coated and uncoated specimens are also monitored during the fatigue test. Paper includes a German-language abstract.

In this paper, plasma sprayed thermal barrier coatings (TBCs) with and without bond coat are stressed to various stress levels under four point bending with in situ acoustic emission (AE) to monitor any cracking activities. Micro- and macro-cracks occurring during the tests are investigated to better understand the failure mechanisms of TBCs. The results show that limited AE activities were detected in the first four stress-relief cycles, while plastic deformation and the greatest AE activity were observed when the applied load exceeded the yield point. In addition, they show that a TBC system that contained an adhesive layer had less AE activity (cracking events) than the TBC without an adhesive layer. In addition, the samples tested at a main speed of 5 micrometer/s resulted in a higher AE activity than the samples tested at 10 micrometer/s. With increasing plastic deformation, macro cracks and surface cracks also occurred. Paper includes a German-language abstract.

In this paper, the mechanical properties and cracking features of yttria stabilized zirconia with and without bond coat on steel substrates is investigated. Four point bending tests have been used to evaluate the mechanical properties, while acoustic emission (AE) has been used to in situ monitor the cracking behavior during the bend tests. In the sprayed state, the samples were characterized by four-point bending tests with local noise emission. In comparison with the substrate, the coated samples showed an increased flow pressure. It is also shown that the processing parameters, the cooling, and the adhesive layer have a significant influence on the flow pressure. It is proven that the cooling affects the behavior of the load-displacement curves. The AE analysis shows the different deformation behavior of the coating-substrate system for the different processing conditions. This is supported by the surface crack analysis. Paper includes a German-language abstract.