• Marrocco, Tiziana
• Mccartney, D. Graham
• Harris, S. J.
• Driver, L. C.

Abstract

<p>Al-20wt%Sn-1%Cu coatings have been produced by high velocity oxy-fuel (HVOF) thermal spraying onto steel sheet, and then fabricated into shell bearings for use in automotive engines. To seek further improvements in the bearings, quaternary alloy coatings were prepared from gas atomised Al-20Sn-1Cu-2Ni and Al-20Sn-1Cu-7Si powders. The powders and coatings were characterised by SEM, TEM and XRD. Microhardness and wear properties were measured on the coated samples. As-sprayed deposits contained splats which had been either fully molten or partially melted during flight. These contained a β-Sn phase dispersed as 50-200 nm particles on solidification. The Ni containing powders had a Ni-containing phase present, which was reduced in quantity during spraying and partially restored during post-spray annealing at 300°C. Coating hardness decreased from 120 to 70Hv whilst annealing. Si was present in the powder and in the assprayed and heat treated Al-Sn-Cu-Si coatings. Si in the powder was 1-5 μm in size but this was greatly reduced in the coatings. XRD and TEM provided evidence of Si precipitation in heated treated coatings. The microhardness of the as-sprayed coating was ∼130Hv and this reduced to ∼65Hv after heat treatment. Wear resistance of the annealed Si containing coatings was superior to those of Al-Sn-Cu and Al-Sn-Cu-Ni coatings.</p>

Topics

• phase
• scanning electron microscopy
• x-ray diffraction
• wear resistance
• steel
• hardness
• transmission electron microscopy
• precipitation
• annealing
• Ni-containing