NiCrAlYSi-BaF 2 /CaF 2 -Polyester material was developed for abradable seal of high-pressure compressor in gas turbine. The NiCrAlYSi-BaF 2 /CaF 2 -Polyester coatings were deposited on Ni-based superalloy substrates with an air plasma spray system. Friction and wear properties of the coatings were investigated in view of friction coefficient and wear morphologies of the coatings. The morphologies of the coatings were evaluated by field emission scanning electron microscopy. The results showed that NiCrAlYSi-7%BaF 2 /CaF 2 -10%Polyester coating exhibits lower macrohardness, lower friction coefficient and excellent abradability.

This study investigates a new zirconia-based ceramic for potential use in thermal barrier coatings. In the experiments, Sc 2 O 3 -Gd 2 O 3 -Yb 2 O 3 -ZrO 2 (SGYZ) powder was synthesized by coprecipitation and calcination, then agglomerated and sintered to facilitate spraying. The structure, morphology, and phase stability of the powder and plasma-sprayed SGYZ coatings were analyzed and thermal conductivity was measured. Test results show that the powders and coatings have good phase stability even after 500 h at 1400 °C and do not undergo tetragonal-to-monoclinic phase transition upon cooling. Plasma-sprayed SGYZ also has a lower thermal conductivity than YSZ, which is currently used in gas turbine engines.

Zirconia stabilized with a combination of scandia and yttria (ScYSZ) powder for plasma spraying was synthesized by chemical coprecipitation process in the experiment, and the ScYSZ powder contains 7.0mol% scandia and 1.5mol% yttria. The microstructure, phase stability and thermal conductivity of plasma sprayed ScYSZ thermal barrier coatings (TBCs) were investigated. The results revealed that the ScYSZ TBCs had excellent stability to retain single metastable tetragonal t′phase even after high temperature (1500 °C) exposure for 300 hours and did not undergo a tetragonal-to-monoclinic phase transition upon cooling. Furthermore, the ScYSZ TBCs had lower thermal conductivity than 3.5-4.5mol% yttria-stabilized zirconia TBCs currently used in gas turbine engine industry. ScYSZ TBCs could be developed as a novel TBCs for advanced gas turbine engines.

The pore structure in nano-porous TiO 2 coating influences the ion diffusion property and photovoltaic performance of dye-sensitized solar cells (DSC). In this paper, TiO 2 coatings were deposited by vacuum cold spray (VCS) using a strengthened nanostructured powder. The pore structure, ion diffusion and dye infiltration properties were examined to understand the deposition mechanism of the coating and the suitability of cold sprayed TiO 2 coating for DSC. It was interestingly found that the pores in the VCS TiO 2 coating presented a bimodal size distribution with two peaks at ~15 nm and ~50 nm, which contributed to a much higher ion diffusion coefficient comparing to that of the conventional unimodal-sized nano-porous coating. The dye infiltration and loading are beneficial from the bimodal size distribution of the pores. Based on the impact behavior of the spray powder, a deposition model was proposed to explain the deposition mechanism of the strengthened nanostructured powder during vacuum cold spray.

Nanostructured chromium oxide coatings were deposited on stainless steel with an axial powder feeding plasma spray system. Friction and wear properties of the coatings were investigated in view of friction coefficient and volumetric wear loss of the coatings with a SRV oscillating friction and wear tester in a ball-on-disc configuration. The morphology and microstructure of the coatings were evaluated by light microscopy, field emission scanning electron microscopy and X-ray diffraction. The results showed that the nanostructured chromium oxide coatings were harder and had a lower friction coefficient and much better wear resistance than the conventional chromium oxide coatings.

The technology and thermal shock properties and thermal conductivity of plasma sprayed nanostructured yttria-stabilized zirconia thermal barrier coatings (TBCs) are studied in this paper. The TBCs on the substrate of Ni 3 Al based alloy IC-10 were fabricated by using the nanostructured yttria-stabilized zirconia powder under certain plasma spraying conditions. By manipulating the plasma spray process, nanostructured TBCs were obtained. The specimens were thermally shocked from 1000°C, 1100 °C and 1200°C into 20°C water and the morphology and microstructure of the TBCs were evaluated by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal diffusivity was tested by a laser pulse method. The results showed that the nanostructured TBCs had more than 30% reduction in thermal conductivity and the thermal shock lifetimes were much longer than that of the conventional TBCs.

This article describes a series of experiments that were conducted on flash memory devices to correlate the defects that are detected by photon emission microscopy (PEM) and laser-induced techniques. Currently, there are two main categories of fault localization techniques for failure analysis, namely passive and active techniques. The article discusses defect localization by PEM and SOM. Three types of defects are described: Type 1 defects are those that can be accurately localized by both PEM and laser-induced techniques; Type 2 defects are defects which can only be detected with PEM and are not observable with laser-induced techniques; and Type 3 defects are those that are detectable with laser-induced techniques but cannot be detected by PEM. While PEM is able to capture the symptoms of existing leakage defects, laser-induced techniques can precisely localize temperature sensitive defects.

Reducing operating clearance between the HP turbine and shroud is a means often used by engine manufacturers to improve the efficiency of new generation gas turbines. This, in turn, requires the development and use of clearance control coatings to minimize the effects of degradation and wear associated with rubbing. In this study, the authors assess two coating systems: VPS NiCoCrAlYTa coatings for blade tips and plasma-sprayed MCrAlY, a potential abradable coating. In order to understand the wear mechanisms of these systems, block-on-ring and fretting tests were conducted and the relationship between microstructure and wear was examined. The results were then compared to those of rub tests performed with real engine components.