Composition of non-metallic inclusions and microstructure of electric arc coating formed using the flux-cored wire of Fe – C – Si – Mn – Сr – Ni – Mo system

Abstract

The article considers the study of composition of the non-metallic inclusions and microstructure of the electric arc coating using the flux-cored wire of Fe – C – Si – Mn – Cr – Ni – Mo system. Formation of the electric arc coating was carried out using the ASAW-1250 automatic arc welding machine by the investigated wire. In order to influence the level of contamination of the deposited metal with non-metallic oxide inclusions, aluminum gas purification dust was introduced into the flux-cored wire (instead of amorphous carbon). Composition of the electric arc coating was determined using XRF-1800 spectrometer. Microstructure of the electric arc coatings was studied by optical microscopy. The phase and elemental compositions were studied using scanning electron microscopy on MIRA 3 LMH instrument. Non-metallic inclusions in the electric arc coating consist of oxides of silicon, fluorine, calcium, aluminum and magnesium oxides. The darker component in the inclusion, which looks like rectilinear crystals directed from the surface deep into the inclusion, has a similar phase composition, but differs somewhat in the content of chemical elements. A small dark component of a rounded shape (aluminum and magnesium oxides) is observed in the inclusion. Traces of sulfur are highlighted along the contour of the globules. Metallographic analysis of the deposited surface showed that the microstructure of the deposited layer is a coarse-needle martensite. The structure is uniform, has a dendritic (columnar) structure characteristic for cast metal. The results of the conducted investigations allow measures to be developed to reduce the content of non-metallic inclusions containing elements of fluorine, sodium and aluminum, which in turn may adversely affect the physical and mechanical properties of the deposited layer, for example, by using refining additives to reduce the contamination of the deposited layer with non-metallic inclusions.