Microstructure characteristic and corrosion resistance of pressure resistance seal welded joint of clad tubes
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The zirconium alloy clad tube provides a protection and room for the nuclear reaction of fuel rods in the nuclear power plant. The clad tubes are usually sealed up by pressure resistance welding with the end plugs. The nonequilibrium physical metallurgy, caused by welding, often brings about a non-uniformity of microstructure and corrosion resistance in the zirconium alloy joint. In order to investigate the influence of the microstructure on the service performance of the welded joint corrosion experiments were designed and conducted by amplifying the mechanical and heat-affected zone in the joint, using a thermal and mechanical simulation machine. It was shown that the amplified sample had the similar microstructure and micro hardness with the mechanical and heat-affected zone. The corrosion rate of the mechanical and heat-affected zone was higher than that of the base metal of the clad tube. A heat treatment after welding was proposed to weaken the influence of microstructure difference on its corrosive resistance. It was shown that the corrosive resistance could be improved by modifying the microstructure appearance and the distribution of the second phase particles
Abstract
The zirconium alloy clad tube provides a protection and room for the nuclear reaction of fuel rods in the nuclear power plant. The clad tubes are usually sealed up by pressure resistance welding with the end plugs. The nonequilibrium physical metallurgy, caused by welding, often brings about a non-uniformity of microstructure and corrosion resistance in the zirconium alloy joint. In order to investigate the influence of the microstructure on the service performance of the welded joint corrosion experiments were designed and conducted by amplifying the mechanical and heat-affected zone in the joint, using a thermal and mechanical simulation machine. It was shown that the amplified sample had the similar microstructure and micro hardness with the mechanical and heat-affected zone. The corrosion rate of the mechanical and heat-affected zone was higher than that of the base metal of the clad tube. A heat treatment after welding was proposed to weaken the influence of microstructure difference on its corrosive resistance. It was shown that the corrosive resistance could be improved by modifying the microstructure appearance and the distribution of the second phase particles