A series of iron based hardfacing alloys with varying tungsten contents were fabricated using slag free self-shielded flux cored wire, and the effects of tungsten addition on microstructure and wear performance were investigated. The experimental results showed that the iron base tungsten free hardfacing alloy has a typical hypereutectic microstructure, which consists of primary hexagonal M7(C, B)3 carbides and eutectic long bar-like M3(C, B) carbides in the austenite and martensite matrix. The addition of tungsten increases the size of primary hexagonal M7(C, B)3 carbides and promotes the formation of martensite, as well as changes the morphology of eutectic carbides. It was found that the eutectic carbides change from the long bar-like shape to the scattered web shape with the increase in tungsten content to 9 wt-, and subsequently change to the plate shape with further increasing the tungsten content to 12 wt-. For the all tungsten containing hardfacing alloys, tungsten exists in both the carbides and matrix uniformly. Results also showed that the wear loss of the sample with 9 wt- tungsten was the smallest among all the samples owing to the higher hardness and reinforced microstructure.

The iron based hardfacing alloys were produced using slag free self-shielded flux cored wires with varying niobium contents. The results show that NbC acted as the nucleus of primary M 7 (C, B) 3 (M5Cr, Fe mainly) carbides and decreased the amount of M 7 (C,B) 3 carbides when niobium was added into the alloys. When 18 wt-%Fe-Nb (60 wt-%Nb) was added, the microstructure of hardfacing alloy transformed from hypereutectic structure to a eutectic one due to the formation of NbC, which consumed a mass of carbon. The microstructure changed into a hypoeutectic structure when the Fe-Nb content was up to 24 wt-%. With the increase in Fe-Nb content, the main abrasive wear mechanism changed from microcracking to microcutting and microploughing due to the formation of NbC and the reduction of primary M 7 (C, B) 3 carbides. The wear loss of the alloy with 18 wt-%Fe-Nb addition was the smallest among all the alloys.

The corrosion resistance of slag‐free self‐shielded metal‐cord welding overlay with different ferrotitanium additions in alkaline solution (pH=14) was investigated. The results show that the self‐corrosion potential Ecorr is the highest and the self‐corrosion current density Icorr is the minimum when the addition of ferrotitanium is 6 wt. %. titanium carbide corrodes before other carbides in alkaline solution due to the absence of iron. A ferrotitanium addition of 6 wt. % can provide the best corrosion resistance to the fabricated welding overlays, as an increased ferrotitanium addition will result in a decrease in chromium carbide and an increase in titanium carbide, of which titanium carbide is the most prone to corrosion, followed by chromium carbide, and finally the austenitic matrix.