Simulation of the welding of irradiated materials
Helium was uniformly implanted using the ''tritium trick'' technique to levels of 0.18, 2.5, 27, 105 and 256 atomic part per million (appm) for type 316 stainless steel, and 0.3 and 1 appm for Sandvik HT-9 (12 Cr-1MoVW). Both full penetration as well as partial penetration welds were then produced on control and helium-containing materials using the autogenous gas tungsten arc (GTA) welding process under full constraint conditions. For full penetration welds, both materials were successfully welded when they contained less than 0.3 appm helium. However, welds of both materials, when containing greater than 1 appm helium, were found to develop cracks during cooling of the weld. Transmission and scanning electron microscopy indicated that the HAZ cracking was caused by the growth and coalescence of grain boundary (GB) helium bubbles. This cracking occurred as a result of the combination of high temperatures and high shrinkage tensile stresses. The cracking in the fusion zone was found to result from the precipitation of helium along dendrite interfaces. A model based on the kinetics of diffusive cavity growth is presented to explain the observed results. The model proposes a helium bubble growth mechanism which leads to final intergranular rupture in the heat-affected zone. Results of the present study demonstrate that the use of conventional fusion welding techniques to repair materials degraded by exposure to irradiation environments may be difficult if the irradiation results in the generation of helium equal to or greater than 1 appm.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5846771
- Report Number(s):
- ORNL/TM-11158; ON: DE89015656
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360101 -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
360106* -- Metals & Alloys-- Radiation Effects
AGING
ALLOYS
ARC WELDING
AUSTENITIC STEELS
BUBBLES
CHROMIUM ALLOYS
CHROMIUM-NICKEL STEELS
CHROMIUM-NICKEL-MOLYBDENUM STEELS
CORROSION RESISTANT ALLOYS
CRACKS
CRYSTAL STRUCTURE
DIFFUSION
ELECTRON MICROSCOPY
ELEMENTS
EMBRITTLEMENT
FABRICATION
FLUIDS
GAS TUNGSTEN-ARC WELDING
GASES
GRAIN BOUNDARIES
HEAT AFFECTED ZONE
HEAT RESIS
HELIUM
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
IRRADIATION
JOINING
MECHANICAL PROPERTIES
MICROSCOPY
MICROSTRUCTURE
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NONMETALS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
RARE GASES
SCANNING ELECTRON MICROSCOPY
STAINLESS STEEL-316
STAINLESS STEELS
STEEL-CR17NI12MO3
STEELS
TENSILE PROPERTIES
WELDABILITY
WELDING
ZONES