Feasibility assessment of local repairment for reformer furnace tubes in service exposure

The reformer furnace tube in service exposure after local replacement was investigated on the microstructure and mechanical properties. Experimental results indicate that NbC carbide transforms into G phase in service exposure and the precipitates coarsen with the distance increasing. Meanwhile, the linked cavities distribute in the scope of 8.7 m–10.5 m. The tensile properties and micro-hardness exhibit a continuous decrease followed by a stable level and then a slight increase with the distance increasing for the “new” tube. Based on the microstructural observations and theoretical calculation, the highest damage part of the “new” tube is located at 8.7 m–10.5 m and the damage level is higher than that of the “old” tube. The damage distribution is comparatively homogeneous along the direction of wall thickness. Due to the good condition of the whole tube, the feasibility of the local repairment has been confirmed.