Effect on residual stresses in plasma sprayed Al-Si/B4C composite coatings subjected to thermal shock

Al-Si/B4C composite coatings were deposited on metallic substrates using an atmospheric plasma spray technique for diesel engine motor applications. The effect on residual stresses of the reinforcement particle (B4C) content, coating thickness and porosity of Al-Si/B4C coatings on Al-Si alloy substrate were investigated by the finite element method (FEM). The coatings were characterized by means of optical microscope. Thermal loads were applied to the model at a temperature of 550 °C using FEM. Metallographic analysis of the coatings proved the existence of porosity and reinforcement particle. It was found that the volume content of the B4C phase was in the range of 5-25%, and the porosity had a content at 0-14 vol.%. The coating thickness was in the range of 100-1000 μm. Finite element calculations demonstrated that the thermal shock resistance decreased with the increase of the reinforcement particle content, the increase in coating thickness and with porosity contents of over 4 vol.%. Of the coating systems, Al-Si/20% B4C coating possess the highest thermal shock resistance. © 2004 Elsevier B.V. All rights reserved

Wear behaviour of plasma-sprayed AlSi/B4C composite coatings

This paper describes the wear behaviour of AlSi/B4C composite coatings with 0-25 wt% B4C particles for diesel engine motors. These coatings were successfully fabricated on AlSi substrates using an atmospheric plasma spray technique. The produced samples were characterized by means of an optical microscope, scanning electron microscope and microhardness tester. The obtained results pointed out that an increase of B4C particles in AN coatings was caused on the rising of the microhardness values and the decrease of the thermal expansion coefficient of the coatings. The friction and wear experiments were performed under dry conditions using a ball-on-dics configuration against WC/Co counter material for different loads. It was concluded that wear resistance of the coatings produced using B4C powders is greatly improved compared with the substrate material. The highest wear resistance of the coatings were also determined in the 20% B4C coating. (c) 2006 Elsevier Ltd. All rights reserved

Al-Si/B4C composite coatings on Al-Si substrate by plasma spray technique

Plasma-sprayed coatings of Al-Si/B4C have been prepared on Al-Si piston alloys for diesel engine motors. The Al-Si/B4C composite powders including 5-25 wt% B4C were prepared by mixing and ball-milling processes. These powders were deposited on Al-Si substrate using an atmospheric plasma spray technique. The coatings have been characterised with respect to phase composition, microstructure, microhardness, bond strength and thermal expansion. It was found that Al, Si, B4C and Al2O3 phases were determined in the coatings with approximately 600 mu m thick by using X-ray diffraction analysis. Scanning electron microscope observation revealed that boron carbide particles were uniformly distributed in composite coatings and B4C particles were fully wetted by Al-Si alloy. Also, no reaction products were observed in Al-Si/B4C composite coatings. It was found that surface roughness, porosity, bond strength and thermal expansion coefficient of composite coatings decreased with increasing fraction of the boron carbide particle. It was demonstrated that the higher the B4C content, the higher the hardness of coatings because the hardness of B4C is higher than that of Al-Si. (c) 2006 Elsevier Ltd. All rights reserved