• THE EFFECT OF ADDING NIOBIUM ELEMENT (Nb) ON METALLURGICAL PROPERTIES OF Fe-Cr-C HARDFACING

    Machines. Technologies. Materials., Vol. 10 (2016), Issue 4, pg(s) 36-39

    in this study, the hard facing with Fe-Cr-C base welded wire and Fe-Cr-Nb-C cored welding wire by using submerged-arc welding method in single-pass, two-pass and three pass over the pieces of carbon steel (St37 )was done. Cored welding wire Fe-Cr-Nb-C by an approximate ratio of 5.41 Cr to C ratio, was containing 5.6 to 7% of the niobium element. scanning electron microscopy, optical microscopy, X-ray diffraction and point analysis, indicates the presence of carbides (Fe, Cr)7C3 and Nb2C in hardened samples with Fe-Cr-Nb-C welding wire. The results showed that with increasing number of hardened passes, the percentage of carbon, chromium and niobium concentrations increased and as a result the dilution percent was decreased that cause to increasing hardness and better performance. test results indicate higher hardness of hardened samples with Fe-Cr-Nb-C welding wire compared to samples hardened with Fe-Cr-C welded base wire. With increasing number of of hard passes, hardness was increased, so that the highest and lowest hardness is related to three pass samples that was hardened with metal cored wire Fe-Cr-Nb-C.The reason of increased hardness in three-pass samples hardened with Fe-Cr-Nb-C metal cored wire was to with increasing in the number of hardened passes , dilution rate was reduced by the base metal and this cause to coarse and more uniform distribution of carbides .