International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This paper presents an overview of hybrid technologies for joining dissimilar materials in automotive applications. CMT welding/brazing technology has been experimentally verified for the purpose of joining dissimilar steels or steels and aluminium alloy. Two types of filler material were used, one based on Cu and the other based on Al. When joining dissimilar steels, a true brazed joint was formed, while when joining steels and aluminium, a hybrid – welded/brazed joint was formed. Subsequently, metallographic analysis of the joints and testing of their load carrying capacity was carried out.

In this research work were analyzed the reasons for fracture of pin machined from 42CrMo44 steel. One pine build in TBU (Tread Brake Unit) of railway wagon breaking system was broken in exploratory condition. Reclamation from purchaser was sent to the producer concerning occurred fracture of pin. Producer sent request to the team of the Faculty of Technology and Metallurgy to perform investigations and to determine the reason of fracture (failure analysis). It was decided to perform the following investigations: visual inspection, determination of chemical composition, hardness measurement, metallographic investigations which include analysis of microstructure and quantitate determination of nonmetallic inclusions. For comparison of results, raw material for pin production i.e. solid bars φ50, and new none used bar from the same steel was investigated too. Performed investigations showed that the main reason for the fracture of pin is the quality of the raw material more concretely segregation of chemical elements and increased concentration of nonmetallic inclusions.

In this research work, metallographic investigation of two parts which are implemented to railway wagons breaking system was performed. Both parts are produced from EN-GJS-500-7 nodular iron. One of delivered parts leading nut (part 1) was broken during the exploitation and the second part working nut (part 2) was new. Metallographic investigation based on standard EN 945-1was implemented in order to check the quality of the parts. The reason for breaking of part 1 one was analyzed too. After metallographic preparation, the polished specimens they were analyzed under optical microscope in order to determine form, size, density and distribution of graphite per unite area as first graphite nodules were analyzed after that microstructure of nodular iron. Figures from optical microscope were compared with reference images under the same magnification. After etching the specimens their microstructure was analyzed. It was concluded that quality of the part 2 is much better concerning the requirement of the EN 945 -1 standard.