Rotary Friction Welding of Molybdenum without Upset Forging

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.

Mechanical Performance and Microstructural Evolution of Rotary Friction Welding of Acrylonitrile Butadiene Styrene and Polycarbonate Rods

“…As can be seen, the increase in joint strength and surface hardness with increasing rotation speed is observed. This result reveals that the surface hardness, flexural strength, and impact energy are directly proportional to the rotation speed of RFW [28]. Figure 8 shows the number of meshes as a function of peak temperature in the weld joint.…”

Microstructure and Mechanical Properties of Solid-State Rotary Friction Welded Inconel 713C and 32CrMo4 Steel Joints Used in a Turbocharger Rotor

“…In previous works, Skowrońska et al [ 29 ] found that the character of the weld in a dissimilar joint is based on deep plastic deformation without visible diffusive processes in the interface zone. Xie et al [ 30 ] analysed the effects of welding parameters on microstructure, tensile strength, and microhardness in RFWed joints produced without upset forging on pure molybdenium rods. The molybdenium joints had asymmetric, spiral shaped flashes.…”