Abstract: Multiple cracks were found at the catalytic flue gas pipes and expansion joint during the maintenance period of a certain company. Due to the excellent high-temperature mechanical properties of nickel based alloys, they are widely used in the petrochemical industry. Therefore, this paper explores the feasibility of repairing cracks with nickel based welding material ENiCrFe-3 to address the above issues. To maintain consistency with the actual engineering, welding tests were conducted using 304H as the base material and NiCrFe-3 as the filler metal and a combination of argon arc welding and electrode arc welding was adopted. After the welding, high-temperature mechanical tests and metallographic structure inspections were conducted on the welded joints. The mechanical test results show that the high-temperature tensile and high-temperature impact properties of the welded joint are better than those of the base metal. The impact fracture morphology is mainly ductile dimples, and its overall hardness value is between 200 HV and 230 HV with little change. The metallographic examination results show that the fusion between the welding material and the base material is good, and there are no defects such as cracks or pores. The above results indicate that NiCrFe-3 can be used for welding catalytic flue gas pipes.

Key words: nickel based alloy, manual arc welding, catalytic flue gas pipe, mechanical properties, metallographic structure