Abstract
In this research work, the weldability of low alloyed AISI 4340 aeronautical steel and AISI 304L austenitic stainless steel joined by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) techniques, using ER309L and ERNiCr-3 filler metals was investigated. The main focus of the study involves the investigation on the effect of continuous and pulsed current mode of GTA welding process on the metallurgical and mechanical properties of these dissimilar weldments. Microstructure studies revealed the formation of different zones across the weldments, vis-a-vis martensite at the HAZ of AISI 4340, vermicular δ - ferrite /ferrite stringers at the HAZ of AISI 304L, pearlite colonies at the parent metal of AISI 4340 and equi-axed cellular and/or columnar dendrites at the weld zone. Tensile results showed that current pulsing accrued better tensile properties. The structure - property relationships of these weldments were established based on the current modes employed by utilizing combined techniques of optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).
Highlights
In industrial practice, it is beneficial to join dissimilar materials due to the effective and economical utilization of the special properties of each material
Macrograph examination of the weldments. It is evident from the visual examination (Figure 1) that the sound weld joints of AISI 304L and AISI 4340 shall be achieved on employing both Continuous Current (CC) and Pulsed Current Gas Tungsten Arc (PCGTA) welding modes
C) Narrow weld beads could be produced on employing PCGTA welding, which in turn lowers the width of heat-affected zone (HAZ)
Summary
It is beneficial to join dissimilar materials due to the effective and economical utilization of the special properties of each material. Dissimilar metal welding (DMW) is widely used in power plants, chemical and petrochemical industries, as well as for nuclear and marine applications, due to the accrued demand from the design and economic point of view These joints are designed to meet much severe service conditions requiring oxidation resistance and high temperature mechanical properties. Mohandas et al.[17] compared the effect of Continuous Current (CC) and Pulsed Current Gas Tungsten Arc (PCGTA) welding techniques on the metallurgical and mechanical properties of ultra-high strength steel. This work assumes potential significance in the areas where these combinations are employed In this investigation, an attempt has been made to compare the weldability, metallurgical and mechanical properties of AISI 4340 and AISI 304L using Continuous Current (CC) and Pulsed Current Gas Tungsten Arc (PCGTA) welding techniques, employing ER309L and ERNiCr-3 filler metals. Combined techniques of Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis were employed to intercept the structure - property relationships of these weldments
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