Study on ductility dip cracking susceptibility in Filler Metal 82 during welding

Abstract

In this paper, Ductility Dip Cracking (DDC) susceptibility in Inconel600 companion Filler Metal 82 (FM82) under different stress states is investigated. Inconel600 is a Ni-Cr-Fe alloy with excellent resistance to general corrosion, localized corrosion, and stress corrosion, which has been widely used in nuclear power plants. However, the companion FM82 has been shown to be susceptible to DDC in welding process. To resolve the problem, this work is mainly focused on evaluating DDC susceptibility in FM82 in welding process. First of all, Strain to Fracture (STF) test is used to achieve the DDC criterion under simple stress state, and the formation mechanism of DDC was explained. Real welding is a process with complex stress state. Later, to get the DDC susceptibility under complex stress state, models about multi-pass welding were built up by means of finite element method. According to numerical simulation results, relationship of deformation and temperature history is achieved. Moreover, susceptible locations and moments could be determined associated with STF results. The simulation results fairly agree with welding experiment from another research.

Computational weld mechanics simulation of hot crack nucleation

“…This thesis attempts to develop a method to estimate the risk of hot cracking nucleation in the design stage using CWM. It should be noted that data for material resistance to hot cracking would normally be determined by experimental tests and are obtained from the literature [1,3]. The data for material resistance to hot cracking includes hot cracking susceptibility temperature range (i.e., BTR and DTR), critical strain increment and critical strain rate.…”

“…One explanation is that DDC nucleates as an applied shear stress causes voids to pile up and eventually coalesce [7]. DDC is also thought to be caused by grain boundary sliding and loss of cohesive strength [7].…”

“…One explanation is that DDC nucleates as an applied shear stress causes voids to pile up and eventually coalesce [7]. DDC is also thought to be caused by grain boundary sliding and loss of cohesive strength [7]. Ramirez et al [25] attributed the drop in inter-granular strength to impurity and interstitial element segregation to grain boundaries, grain size and grain boundary orientation.…”

“…The intragranular is predominately intra-granular, since intra-granular strength is below defor mation causes the movement of dislocations that leads to hardening. This means as temperature drops below the DTR, resistance to DDC increases [1]. As temperature increases above the BTR region, the material resistance to DDC increases, which is attributed to the recrystallization that prevents crack nucleation [1].…”

“…This research focuses on hot cracking, one of the numerous types of weld de fects. The topic of this thesis was driven by the increasing demand from the nuclear, aerospace and other sectors for materials that maintain strength/stiffness at high temperatures and are corrosion resistant [1]. Examples of materials that satisfy these performance needs are nickel (Ni) based super alloys and stainless steels.…”