Investigation of Weldability in High-Cr Ni-base Filler Metals
type: CreativeWork
description: High-Cr Ni-base alloys have been used in the nuclear industry for weld overlay repair of dissimilar metal welds which have been affected by primary water stress corrosion cracking. During welding, defects may result from super-solidus and sub-solidus cracking phenomena. The ability to evaluate and quantify the degree to which a given alloy is susceptible to each cracking mechanism is of great importance in alloy selection, alloy development and weld design. The first aim of this project was to improve the reliability of the cast pin tear test (CPTT) as a tool for evaluation of solidification cracking susceptibility. The second aim was to evaluate the weldability of a new heat of Inconel alloy 52MSS (ERNiCrFe-13) with reduced iron content as well as a single heat of Kobelco 690NB (ERNiCrFe-7A) comparing these materials with other available alloys of the same type.The incorporation of levitation melting has enabled precise control of the casting process in the CPTT. Active temperature monitoring during melting enables control of the casting temperature with a standard deviation of 8.8 C. Gradual reduction in the power applied to the coil has enabled focused transfer of the charge into the mold. Thermocouple measurements indicated that the cooling rate during solidification in the CPTT was approximately twice that which is experienced in GTAW welding using parameters typical for use in weld overlay repairs. Finite element simulations indicated that a significant reduction in cooling rate of the casting could be obtained by altering the mold material, mold outer diameter or cast pin diameter. Prototype mold screening tests enabled design of a mold that provides a cooling rate of 160 C/s based on FEA modeling, compared with the previous cooling rate of 245 C/s, while maintaining feasibility of the CPTT. A longer pin length is required to cause cracking with the redesigned molds when compared with the previous molds. Also, significant crack healing with Nb-rich eutectic-l…
abstract: High-Cr Ni-base alloys have been used in the nuclear industry for weld overlay repair of dissimilar metal welds which have been affected by primary water stress corrosion cracking. During welding, defects may result from super-solidus and sub-solidus cracking phenomena. The ability to evaluate and quantify the degree to which a given alloy is susceptible to each cracking mechanism is of great importance in alloy selection, alloy development and weld design. The first aim of this project was to improve the reliability of the cast pin tear test (CPTT) as a tool for evaluation of solidification cracking susceptibility. The second aim was to evaluate the weldability of a new heat of Inconel alloy 52MSS (ERNiCrFe-13) with reduced iron content as well as a single heat of Kobelco 690NB (ERNiCrFe-7A) comparing these materials with other available alloys of the same type.The incorporation of levitation melting has enabled precise control of the casting process in the CPTT. Active temperature monitoring during melting enables control of the casting temperature with a standard deviation of 8.8 C. Gradual reduction in the power applied to the coil has enabled focused transfer of the charge into the mold. Thermocouple measurements indicated that the cooling rate during solidification in the CPTT was approximately twice that which is experienced in GTAW welding using parameters typical for use in weld overlay repairs. Finite element simulations indicated that a significant reduction in cooling rate of the casting could be obtained by altering the mold material, mold outer diameter or cast pin diameter. Prototype mold screening tests enabled design of a mold that provides a cooling rate of 160 C/s based on FEA modeling, compared with the previous cooling rate of 245 C/s, while maintaining feasibility of the CPTT. A longer pin length is required to cause cracking with the redesigned molds when compared with the previous molds. Also, significant crack healing with Nb-rich eutectic-l…
author: Luskin, Timothy Clark
language: English
keywords: Materials Science, Metallurgy, weld overlay, nickel, dissimilar metal weld, inconel, weld cracking, solidification cracking, ductility dip cracking, cast pin tear test, weldability testing
date published: 2013-07-24
date modified: 2026-07-24T03:37:46Z
provider: OhioLINK
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The Ohio State University