Effect of Filler Metal on the Oxidation Resistance of 35Cr-45Ni Alloy Weld Metal

In this study the effect of UTP 2535 Nb and UTP 3545 Nb filler metals on the microstructure and oxidation resistance of the weld metal of GTAW welded 35Cr-45Ni alloy have been investigated. According to the results, microstructure of the weld metals includes Cr and Nb Carides precipitating along the grain boundaries of austenitic matrix. Weld metal of the sample welded with UTP 3545 Nb filler metal showed denser and more continuous carbides which arises from higher Cr content in this filler metal. According to the XRD analysis of the oxidized weld metals at 1000 ℃ for 96 h, all samples represent an external oxide layer, mostly consist of Cr oxide and an internal oxide layer, mostly composed of Si oxide. Weld metal of the sample welded with UTP 2535 filler metal showed the highest weight gain (4.3 mg/cm2) and oxide thickness (20 μm). For the weld metal of the other sample, these values were 3.6 mg/cm2 and 11 μm, respectively. It can be attributed to the higher Cr and Si in the UTP 3545 Nb filler metal. The first element results in a resistant, continuous, and defect free external oxide on the surface, and the latter one leads to formation of a resistant internal oxide, both strongly effective in improving the oxidation resistance of the weld zone.