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Two kinds of cored wires were used to deposit coatings containing amorphous phase and nanocrystalline grains by arc spraying. The microstructure characteristics of the coatings were conducted by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD). The microstructures of the both coatings had lamellar morphologies. Both coatings consisted of Fe rich matrix and several kinds of borides. The Fe rich matrix had a majority amorphous phase regions with a fraction of nanocrystalline grains. The coatings' microhardness values for NiB coating is 950 HV(100 g) and for NiB–Cr3C2 coating is 1090 HV(100 g). Compared with the reference sample of Q235 steel, the coatings showed a much higher wear resistance, and the relative wear resistance of the NiB coating is 10 times while the NiB–Cr3C2 coating is 13·3 times higher than that of Q235 steel. [ABSTRACT FROM AUTHOR]

An Fe based cored wire was used to deposit wear resistant coatings containing Fe based amorphous phase and nanocrystallites on Q235 steel substrate by arc spraying. The microstructure of the coatings was investigated by scanning electron microscopy and transmission electron microscopy. Electron probe microanalyser and X-ray diffraction analysis were used to study the chemical compositions and phase compositions in the coatings. The microhardness of the coating was determined. The wear behaviour of the coatings was evaluated. The results showed that the coatings contained Fe based amorphous phase and other crystallites such as Fe2B, Cr2B, M23(C,B)6, Fe3O4 and α-(Fe,Cr). Some of the crystallites show grain sizes of <30 nm. The coatings were hard. Compared with the reference sample of commercial 3Cr13 coating, the coatings showed a much higher wear resistance; the relative wear resistance of the amorphous coating was 8 times higher than that of commercial 3Cr13 coating. [ABSTRACT FROM AUTHOR]

The effects of welding fume on welders' health and the environment are of great interest to occupational hygienists and welding consumable manufactures. Since the welding fume sources from the welding consumables and the flux core of the wire is added in many kinds of materials, the effect of several kinds of adding materials on the fume formation rate of lime titania type flux cored wire were studied. Research results show that adding materials in the flux core can be classified into three categories: the first kind can enhance the fume formation rate, the second can lower the fume formation rate and the third has no effects. Effects of adding material content on the fume formation rate are as follows: fume formation rate is enhanced by increasing the Na2SiF6 content; ilmenite has no obvious effect on the fume formation rate; if the core of the wire is made of right match of metal powders and appropriate weight proportion of the feldspar, the fume formation rate can be greatly lowered; the fume formation rate decreases in a large scale if the feldspar content increases in an appropriate confine. [ABSTRACT FROM AUTHOR]

Four Fe–Cr–C hardfacing alloys with carbon contents of 334–65% were studied. The orientation of primary carbides in the microstructures of hardfacing layers produced by arc surfacing was investigated under controlled cooling conditions. Carbon content and cooling conditions were found to play an important role in determining overlayer microstructures. Increasing carbon content or decreasing Cr/C ratio increased the tendency for primary carbides to be oriented perpendicular to the surface of the overlayers, and the carbides in the microstructure became more compact. Under water cooling conditions, the primary carbides were preferentially oriented perpendicular to the surface, which would be expected to improve wear resistance. At lower cooling rates, primary carbides were oriented randomly. [ABSTRACT FROM AUTHOR]

In this study the fume formation rate (FFR) of the flux cored wire for mild steel produced by three different plants was investigated. The fume chemical composition analysis was obtained by inductively coupled mass spectroscopy (ICP) and X-ray diffraction (XRD). The morphology and granularity of ferrite powder produced by different production processes were obtained by scanning electron microscope (SEM) analysis, and their effects on the FFR of the wire and explanation are also included. In the present paper, results demonstrate that the welding fume contains mainly the oxides of ferrite and manganese (∼50%) with remained evaporations of slag. The ferrite powders produced by different production processes have different morphologies. The morphology of ferrite powders has limited effect on the FFR which fluctuates orderly on a small scale with various granularity distributions of ferrite powders. The FFR is lowered when the granularity of ferrite powders retains between 80 and 120 meshes (&minus210+ 130 μm). [ABSTRACT FROM AUTHOR]