Abstract
Microcracks are always present in the deposited metal of nickel-based alloys and austenitic stainless steels, which affects the safety of the pressure pipes. If compressive stress can be introduced into the cracked position by overlay welding, the time required with ordinary gouging repair welding technology will be significantly reduced, which is practical significance for pressure pipes repair welding. In this work, a stainless-steel T-pipe joint was fabricated using manual metal arc welding with an ER316L wire, and an overlay weld was fabricated using tungsten inert gas arc welding with an ERNiCrFe-7A wire. The overlay thickness was about 10 mm. The contour method was employed to measure the residual stress in the T-pipe joint. The results show that compressive residual stress about 50 MPa is formed in the original ER316L weld, which proves that the residual compressive stress can be obtained in the original weld by surfacing 10 mm thick nickel base alloy on the original weld surface.
Highlights
Ductility-dip cracking (DDC) is a type of solid-state cracking that occurs in a number of engineering materials with austenitic crystal lattice, such as austenitic stainless steel and nickel alloys
The distribution of residual stress in repair welding is related to the length of the repair weld, the constraints of the structure, the formation of a welded joint, and the dimensions of the joint; high tensile stress is always present in the welded zone, and compressive stress will form in the region at a large distance from the weld [9,10,11,12]
The results show that the 10-mm-thick overlay repair process can introduce compressive stress into the crack located in the original weld, which is beneficial for crack closure and can save time and reduce the involved costs
Summary
Ductility-dip cracking (DDC) is a type of solid-state cracking that occurs in a number of engineering materials with austenitic crystal lattice, such as austenitic stainless steel and nickel alloys. If the front of the crack is located in the compressive stress zone, a closure behavior will be observed [14] This phenomenon makes it possible to replace gouged-out repair welds with overlay welds. For the T-pipe joint, if compressive stress can be formed at the microcrack zone as a consequence of the shrinkage of the overlay weld, the crack can be closed, and the possibility of its expansion can be eliminated, resulting in a substantial time saving and economic advantage. Nickel-based alloys were used for overlay repair welding outside the T-joint; in order to determine the effect of weld repairing, the residual stress in the joint was measured via the contour method. The welding process is carefully verified, and the heat input and interlayer temperature are reduced as much as possible to ensure that no new cracks will be produced during the overlay process
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