Marcin Winnicki

Friction Welding of Aluminium and Aluminium Alloys with Steel

The paper presents our actual knowledge and experience in joining dissimilar materials with the use of friction welding method. The joints of aluminium and aluminium alloys with the different types of steel were studied. The structural effects occurring during the welding process were described. The mechanical properties using, for example, (i) microhardness measurements, (ii) tensile tests, (iii) bending tests, and (iv) shearing tests were determined. In order to obtain high-quality joints the influence of different configurations of the process such as (i) changing the geometry of bonding surface, (ii) using the interlayer, or (iii) heat treatment was analyzed. Finally, the issues related to the selection of optimal parameters of friction welding process were also investigated.

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.

Low-Temperature Transformation of Amorphous Sol–Gel TiO2 Powder to Anatase During Cold Spray Deposition

Nanocrystalline TiO2 coatings were successfully deposited on metallic substrate surfaces through low-pressure cold spray. Sol–gel amorphous TiO2 dry gel was for the first time used as a feedstock powder. Agglomerated morphology of the amorphous powder with high-density packing of particles and reduced pores number was an important factor for successful low-pressure cold spraying. However, in the present study one more factor contributing to anchoring of TiO2 particles by cold gas spraying onto a substrate was indicated. This factor enabling effective powder deposition and coating production is based on an exotic for conventional ceramic materials’ plastic deformation of amorphous powder. Furthermore, the detailed analysis of SEM, Raman and XRD measurements clearly demonstrated that amorphous titanium dioxide is transformed into crystalline anatase form during the process of low-pressure cold spraying.