Effect of RE oxides on the microstructure of the coatings fabricated on titanium alloys by laser alloying technique

Effect of magnesium addition on the wetting of alumina by aluminium

Metal matrix composites (MMCs) acquire their improved physical and mechanical properties through the careful reinforcement of their matrices by a variety of light but strong and stable reinforcemen...

Pressure infiltration processes to synthesize metal matrix composites – A review of metal matrix composites, the technology and process simulation

Metal matrix composites (MMCs) have been developed in response to the enormous demand for special industrial materials and structures for automotive and aerospace applications, wherein both high-strength and light weight are simultaneously required. The most common, inexpensive route to fabricate MMCs or metal matrix nanocomposites (MMNCs) is based on casting, wherein reinforcements like nanoceramics, -carbides, -nitrides, elements or carbon allotropes are added to molten metal matrices; however, most of the mentioned reinforcements, especially those with nanosized reinforcing particles, have usually poor wettability with serious drawbacks like particle agglomerations and therefore diminished mechanical strength is almost always expected. Many research efforts have been made to enhance the affinity between the mating surfaces. The aim in this paper is to critically review and comprehensively discuss those approaches/routes commonly employed to boost wetting conditions at reinforcement-matrix interfaces. Particular attention is paid to aluminum matrix composites owing to the interest in lightweight materials and the need to enhance the mechanical properties like strength, wear, or creep resistance. It is believed that effective treatment(s) may enormously affect the wetting and interfacial strength.

Wettability in Metal Matrix Composites

Cermet coatings of WC–17Co were thermally sprayed on carbon steel substrates with 0.4 wt.% C using high velocity oxygen-fuel. The main goal of the investigation was the protection of carbon steel substrates against the attack in contact with molten aluminum using WC–Co coatings. Different spraying conditions were used and the optimal coating (226 μm thickness) was characterized by SEM, XRD, Raman spectroscopy, micro-hardness tests and 3D optical profilometry in order to determine thickness, porosity, chemical composition, mechanical properties and surface roughness. Pull-off adhesion tests were conducted to evaluate the adhesion between coatings and substrate, and thermal cycling tests were also developed. The coated steel substrates were immersed in molten aluminum at different times (1, 2, 5 and 24 h), and the resistance of the coatings to the attack of the molten aluminum alloy was studied. It was observed that the WC–Co was an effective physical barrier against molten aluminum penetration. Just after 2 h of immersion, the uncoated carbon steel suffered aggressive attack by the liquid aluminum, which penetrated and cracked it. Conversely, the coated steel was unaffected after 24 h of immersion due to the protection of the WC–Co coating, which suffered the liquid metal penetration only in the outer 35 μm using 700 °C as the higher temperature. The effectiveness of the WC–Co coating to protect carbon steel substrates against thermal fatigue deterioration and attack by molten aluminum was proved.

T Hane

Papers

Effect of La on the wettability of Al2O3 by molten aluminum