Abstract
A large instantaneous axial forging load is required to be applied for the final stage of rotary friction welding (RFW), which is usually conducive to obtaining clean, compact, and high-quality joints. However, for slender fuel claddings made of molybdenum (Mo) with low stiffness, the instantaneous axial forging load cannot be applied at the final stage of welding. This study carried out RFW tests without upset forging on Mo in the atmospheric environment and investigated the effects of welding time on joint morphology, axial shortening, microstructures, microhardness, tensile strength, and tensile fracture morphology. It found that the excessive and abrupt burning and a lot of smoke were generated around the weld zone during welding and spiral flashes were observed after welding. Under welding pressure of 80 MPa and spindle speed of 2000 r/min, the minimum average grain size and maximum tensile strength can be obtained in 4 s when the welding time is between 2–5 s. Scanning electron microscope (SEM) results show that there were morphologies of a large number of intergranular fractures and a small number of transgranular fractures in the fracture. The above results demonstrated that it is feasible to use RFW without upset forging to seal the last weld spot on upper end plugs of fuel claddings made of Mo in high-pressure inert gas, which would not only obtain reliable welding quality but also seal high-pressure inert gas in cladding tubes. The research results have a practical guiding significance of manufacturing accident-tolerant Mo nuclear fuel cladding.
Highlights
Zirconium alloy is widely used to produce nuclear fuel claddings and core structural parts [1,2,3].when the temperature exceeds 1200 ◦ C, zirconium can react with water vapor to produce large amounts of hydrogen, causing explosions, and release large amounts of heat, further accelerating the melting of a reactor core [4,5]
This study focused on the feasibility of using rotary friction welding (RFW) without upset forging to seal the last weld spots on the upper end plugs of Mo fuel claddings, so as to provide guidance for developing reliable welding technology for fuel claddings made of Mo
This research studied the feasibility of using RFW without upset forging to seal the last weld spots
Summary
Zirconium alloy is widely used to produce nuclear fuel claddings and core structural parts [1,2,3]. It is worth noting that in order to prevent reactions, like oxidation of Mo alloy during welding in atmospheric environment, all RFW tests were conducted in liquid (electric spark machining oils) by Andrzej Ambroziak et al This undoubtedly plays a very good role in inhibiting excessive grain growth of the weld zone, which is worth learning from They did not do a detailed analysis of the mechanical and material properties of the joint. This study focused on the feasibility of using RFW without upset forging to seal the last weld spots on the upper end plugs of Mo fuel claddings, so as to provide guidance for developing reliable welding technology for fuel claddings made of Mo. lower end plugs and the cladding tubes under normal pressure/negative pressure. 2020, 13, 1957 last weld spots on the upper end plugs of Mo fuel claddings, so as to provide guidance for developing reliable welding technology for fuel claddings made of Mo
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