In this study, titanium and aluminum powders mixed in different ratios were deposited on stainless steel substrates by warm spraying. Microstructure and composition of as-sprayed and heat-treated samples were characterized and the effect of adding a third element was assessed. It was found that Al content has a major influence on the thickness and porosity of heat-treated Ti-Al coatings and that adding silicon to the powder mixtures reduces the melting point of Al, causing a loss of Al-Si particles during spraying.

This study evaluates a method for producing carbon fiber composite feedstocks suitable for cold gas spraying. Powders consisting of Al-Si particles and carbon nanofibers were attrition milled at 16.5 Hz and 27.5 Hz for up to 12 h at room and cryogenic temperature. Particle shape and size were examined every hour and carbon fiber integration in the Al-Si matrix was assessed. Detailed results are presented and discussed. In all cases, cryomilled powders had smoother surfaces.

In this work, mechanically alloyed Al–12Si/TiB 2 /h-BN composite powder was deposited onto an aluminum substrate by atmospheric plasma spraying. The results revealed that the mechanical alloying (MA) process has a significant effect on composite powder morphology and in-situ reaction intensity between the selective powders during plasma spraying. In addition, hexagonal boron nitride (h-BN) powder incorporated as a solid lubricant, which has excellent lubricating properties, decomposed into B and N and formed a solid solution after a long period of milling. More specifically, during plasma spraying a large amount of h-BN reacted with Al to form AlN. Unlubricated ball-on-disk testing ring was used to examine the anti wear performance of the coatings. The worn surfaces were examined using scanning electron and energy dispersive spectroscopy to elucidate the wear mechanisms operating at the sliding interface.

Air separation plants employ centrifugal compressors where air and electrical energy are the only raw materials used in the production process. In order to optimize compressor performance and efficiency, abradable coatings, originally developed for gas turbines, have been designed into turbocompressors. This paper describes the optimization and performance improvements achievable using aluminium silicon-boron nitride materials.

Abradable coatings are used in gas-turbine engines to optimize compressor performance by maintaining tight blade tip clearances. The most common such coatings are thermally sprayed Al-Si/polyester, Al-Si/graphite, and Ni/graphite. Al-Si/graphite coatings have performed well in terms of wear but are prone to corrosion, which can lead to spalling and a reduction in engine efficiency. In this paper, we chart the development of a powder-based Al-Si/BN abradable material designed to overcome in-service corrosion and analyze laboratory and engine testing results.

Aluminium silicon alloys have shown favourable properties when used as the matrix for abradable coatings in low pressure compressors of gas turbines [1 and 2]. This paper aims to describe the wear mechanisms found in aluminium silicon based abradables. To this end three thermally sprayed coatings are investigated. Aluminium silicon polyester, aluminium silicon-graphite and the most recently developed, aluminium silicon-hexagonal boron nitride (hBN) examined here are amongst a few of these materials. To be able to design materials to function in as wide a parameter range as possible, a test ng simulating engine mechanisms is required. Tests were conducted using titanium blades at velocities ranging from 250 - 450 m/s, temperatures of ambient to 450°C and controlled incursion rate of 5, 50 and 500 µm/s. The data obtained from these tests is best interpreted in the form of wear maps which characterise the seal performance and therefore are of use to engine and material designers.