Aleksandra Małachowska

Aluminium to steel resistance spot welding with cold sprayed interlayer

ABSTRACT Studies on bonding of aluminium alloys to steels are popular because these are structural materials widely used in a variety of industries. However, joining these dissimilar materials is difficult mainly because of the formation of brittle intermetallic compounds. This paper presents a study on welding aluminium to steel by resistance spot welding. Before the welding, steel surface was covered by cold spraying with the layer of aluminium, nickel and nickel–aluminium. This way, instead of the welding of dissimilar materials, the welding of aluminium to aluminium (or nickel) layer pre-deposited on the steel sample was performed. The feasibility of using interlayers for improving the welding of dissimilar materials was tested using SEM, EDX and XRD. Mechanical properties of welds were investigated by microhardness and shear strength tests. The results showed that the coating allowed to decrease hardness in the welding zone and to increase the shear strength of the weld.

Metallisation of polycarbonates using a low pressure cold spray method

ABSTRACT In many industries, polymers are in great demand due to their low weight and good mechanical properties. However, films and coatings are sometimes applied to improve polymer surface properties. This work presents a study on the metallisation of polycarbonates using a low pressure cold spray (LPCS) method. Two types of commercial powders were selected for the deposition of coatings: (i) tin and (ii) aluminium. The coatings were applied (i) on an unmodified substrate and (ii) on a substrate with an interlayer, which enabled the formation of good adherent aluminium coatings. A light and scanning microscopy was used to analyse the microstructure of coatings. Electrical conductivity was determined using the four-probe method and is discussed in relation to the oxygen content. Moreover, bond strength and microhardness were investigated.