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.

In this study, MCrAlY-Al 2 O 3 composite powders were produced by ball milling and deposited by plasma, HVOF, and cold spraying. The results show that Al 2 O 3 fractions can be well controlled using composite powder due to non-preferential impact debonding of the matrix and Al 2 O 3 . The microstructure of spray powders is well retained in HVOF and cold-sprayed coatings due to the unmelted or partially molten condition of the spray particles. In the case of plasma-sprayed coatings, however, most Al 2 O 3 particles segregate at lamellar interfaces, forming a continuous oxide scale on the splat. The cold-spray coatings exhibit the highest hardness due to the work hardening effect of kinetic deposition.

In this study, WC-CoWC coatings were produced by HVOF spraying using bimodal-structured WC-Co powder with both micro- and nano-sized WC particles. Due to the melting characteristics of the powder during spraying, the microsized particles are retained in the deposit, but the nanosized particles dissolve into the Co matrix, forming a Co-W-C ternary phase. Compared to coatings sprayed from conventional WC-CoWC powder, the bimodal coatings are more resistant to corrosion and wear and are comparable in microhardness.

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.

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.