Development of Fe-Cr-Ti-B based in-situ composite hard surface alloying electrodes

In this study, covered electrodes with high hardness, high abrasion resistance and corrosion resistance were developed as an alternative to commercially used hardfacing electrodes. Considering the economic factors in the production of electrodes, ferro-alloy starting materials and additives have been preferred. In the study, eighteen different compositions of Fe-Cr-B, Fe-Ti-B and Fe-Cr-Ti-B based hardfacing electrodes have been designed. These electrodes, produced by using a mold, were coated on AISI 1010 steel by electric arc welding technique. After the coating, the microstructural examinations of the experimental samples prepared by standard metallographic processes were carried out, their macro and micro hardness was measured, the wear resistance was tested and the corrosion test was applied. Experimental findings show that the hardfacing coating has a homogeneous phase distribution, is metallurgically compatible with the substrate material and has the potential to be used commercially. In the microstructural investigations of hardfacing coatings, α-ferrite, M2B types (Fe2B, Cr2B), MB2 type (TiB2) borides, Fe2Ti and eutectic structures formed by these phases were determined. It has been observed that these structures have contributed significantly to the hardness. According to the micro hardness values measured from the substrate material to the seam peak, increase in hardness beginning from the interface was determined. In the macro hardness test performed on the all surface of the coating, it has been understood that the results showed a very low standard deviation, implying that the coating was carried out homogeneously. Another finding is that there is a relationship between the hardness and wear resistance of the coating. According to the reciprocal wear test performed against Al2O3 ball at different wear loads, it was determined that the Fe13Cr2B5 based coating had the lowest wear rate. However, at low loads, titanium plays an important role in reducing the friction coefficient and the lowest friction coefficient value was obtained from Fe13Ti5B2 based composition. As a result of the potentiodynamic polorization test applied to hardfacing coatings in 0.5 M NaCl solution, it has been determined that chromium plays an effective role on the corrosion resistance of the coating. It was observed that the lowest corrosion rate was measured in the Fe13Cr5B2 based composition with the highest chromium content. As a result, using ferroalloy starting materials, Fe-Cr-B-, Fe-Ti-B and Fe-Cr-Ti-B based hardfacing electrodes were successfully produced and coated on AISI 1010 steel substrate. It was determined that the substrate-coating interface properties of the coated layers are homogeneous, extremely hard, abrasion and corrosion resistant.