TiAl 3 -Al composite coatings are believed to hold promise for extending the service temperature range of titanium alloys used as structural materials. In this study, 0.6 x 40 mm Ti-6Al-4V specimens are coated with a 30 μm thick layer of TiAl 3 -Al by low-temperature HVOF spraying. Cross-sectional imaging shows that the as-sprayed coatings have a dense laminar microstructure and are well bonded to the substrate. Following the initial examination, the coating samples were placed in a muffle furnace, where they were held at 700 °C for up to 1000 h. Mass gain was detected starting at 200 h and remained nearly constant for the remainder of the test. This is an indication of excellent corrosion resistance, which is verified by SEM cross-sectioning and elemental EDS analysis. A brief explanation of the protective mechanism of the coating is provided.

Tubular asymmetric LSCF oxygen transport membranes (OTMs) were prepared on stainless steel substrates by PS-PVD and supersonic air-gas plasma spraying (SAPS). The microstructure of the thermally sprayed OTMs is examined by cross-sectional imaging and oxygen permeability is assessed via oxygen permeation flux measurements carried out at atmospheric pressure in an air-helium gradient. The findings from the cross-sectional analysis and oxygen permeation tests are reported and discussed.

In this study, NiCoCrAlYTa-10%Al 2 O 3 powder was deposited on heat-resistant steel substrates by supersonic atmospheric plasma spraying. Coating microstructure, adhesion strength, porosity, oxygen content, microhardness, and wear resistance were systematically evaluated. The results show that the coatings are dense and well adhered and exhibit excellent wear resistance.

Fundamental properties of Titanium coating prepared by low temperature HVOF process aided by injection of water had been published by our research group. The results showed that low temperature HVOF process provided as a good means for the deposition of comparatively dense Ti coating, however the interconnected pores observed in Ti coating degraded corrosion resistance of Ti coating, therefore it was necessary to manufacture denser Ti coating. Two processes were respectively applied for the densification of Ti coating. One process was to perform post heat treatment for as-sprayed Ti coating with conventional Ti powder as feedstock. The other process was to modify thermal spray powder. Ti powder mixing with spherical glass powder was used to deposit denser Ti coating as a result of shot peening effect of hard glass powder. Finally the corrosion resistance for densified Ti coatings was evaluated by electrochemical characterization.

HVO/AF (High-Velocity-Oxygen/Air-Fuel) WC-17Co and WC-10Co4Cr coatings exhibit great potential in the replacement of electrolytic hard chrome (EHC) coating, and comprehensive properties of such coatings should be not worse than those of electrolytic hard chrome coating. The impingement-resistance of HVAF coatings sprayed on 300M ultra-high strength steel was studied in this paper. As an important property index, the fracture toughness of HVAF WC coatings was measured using micro-indentation method at the load of 9.8, 19.6, 24.5, 29.4 and 49.0N respectively. The cracks resulted from stress concentration in the micro-indentation were analyzed. The impingement-resistance for two HVAF WC coatings and EHC was evaluated according to the ASTM D3170 standard, and steel ball dropping experimentation was performed at the height of 0.61, 1.52, 1.83, 2.36 and 2.59m respectively. The cracks caused by both impingements were analyzed using SEM and optical microscopy in comparison with cracks in micro-indentation test.

The influence of the high velocity air fuel (HVAF) sprayed coating on the fatigue behavior of the low alloy steel was studied at different stress levels. It was observed that only one single main crack initiator existed in the substrate after fatigue at low stress levels, but there were multi-cracks on the substrate surface at high stress level. Detailed investigations showed that the cracks in the HVAF coatings sinuously extended to the interface and deflected thereat along the interface. Consequently, free-standing coating was formed due to its limited bond strength to the substrate and the lower elastic modulus than that of the substrate. The gap between the free-standing coating and the substrate surface was found to be correlated with the stress level. The high stress can greatly degrade the adhesion to the substrate causing the delamination of the coating. The cracks in the HVAF coating had no significant effect on the fatigue life of the substrate.