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American Society for Testing and Materials

Recent advances in friction-stir welding : Process, weldment structure and properties

The metallurgy of zinc-coated steel

Welding Metallurgy of

Wire-feed additive manufacturing (AM) is a promising alternative to traditional subtractive manufacturing for fabricating large expensive metal components with complex geometry. The current research focus on wire-feed AM is trying to produce complex-shaped functional metal components with good geometry accuracy, surface finish and material property to meet the demanding requirements from aerospace, automotive and rapid tooling industry. Wire-feed AM processes generally involve high residual stresses and distortions due to the excessive heat input and high deposition rate. The influences of process conditions, such as energy input, wire-feed rate, welding speed, deposition pattern and deposition sequences, etc., on thermal history and resultant residual stresses of AM-processed components needs to be further understood. In addition, poor accuracy and surface finish of the process limit the applications of wire-feed AM technology. In this paper, after an introduction of various wire-feed AM technologies and its characteristics, an in depth review of various process aspects of wire-feed AM, including quality and accuracy of wire-feed AM processed components, will be presented. The overall objective is to identify the current challenges for wire-feed AM as well as point out the future research direction.

Wire-feed additive manufacturing of metal components: technologies, developments and future interests

A study was conducted on the arc and melting efficiency of the plasma arc, gas tungsten arc, gas metal arc, and submerged arc welding processes The results of this work are extended to develop a quantitative method for estimating weld metal dilution in a companion paper Arc efficiency was determined as a function of current for each process using A36 steel base metal Melting efficiency was evaluated with variations in arc power and travel speed during deposition of austenitic stainless steel filler metal onto A36 steel substrates The arc efficiency did not vary significantly within a given process over the range of currents investigated The consumable electrode processes exhibited the highest arc efficiency (084), followed by the gas tungsten arc (067) and plasma arc (047) processes Resistive heating of the consumable GMAW electrode was calculated to account for a significant difference in arc efficiency between the gas metal arc and gas tungsten arc processes A semi-empirical relation was developed for the melting efficiency as a function of net arc power and travel speed, which described the experimental data well An interaction was observed between the arc and melting efficiency A low arc efficiency factor limits the power delivered to the substrate which, in turn, limits the maximum travel speed for a given set of conditions High melting efficiency is favored by high arc powers and travel speeds As a result, a low arc efficiency can limit the maximum obtainable melting efficiency

Thermal efficiency of arc welding processes

Phase transformations in ferrous alloys

The solidification reaction sequences of experimental superalloys containing systematic variations in Fe, Nb, Si, and C were studied using differential thermal analysis (DTA) and microstructural characterization techniques. The reaction sequences responsible for microstructural development were found to be similar to those expected in the Ni-Nb-C ternary system and commercial superalloys of comparable composition. The solute-rich interdendritic liquid generally exhibited two eutectic-type reactions at the terminal stages of solidification: L → (γ+NbC) and L → (γ+Laves). The Ni-base alloys with a high C/Nb ratio represented the only exception to this general solidification sequence. This group of alloys terminated solidification with the L → (γ + NbC) reaction and did not exhibit the γ/Laves constituent. At similar levels of solute elements (Nb, Si, and C), the Fe-base alloys always formed more of the γ/Laves eutectic-type constituent than the corresponding Ni-base alloys. Silicon additions also increased the amount of the γ/Laves constituent that formed in the assolidified microstructure, while C additions promoted formation of γ/NbC. The influence of Nb was dependent on the C content of the alloy. When the C content was low, Nb additions generally promoted formation of γ/Laves, while Nb additions to alloys with high C led to formation of the γ/NbC constituent. The results of this work are combined with quantitative analyses for developing γ-Nb-C pseudoternary solidification diagrams in a companion article.

Solidification of nb-bearing superalloys : Part I. Reaction sequences

Super austenitic stainless steels are often welded using high Mo, Ni base filler metals to maintain the corrosion resistance of the weld. An important aspect of this processing is the weld metal dilution level, which will control the composition and resultant corrosion resistance of the weld. In addition, the distribution of alloying elements within the weld will also significantly affect the corrosion resistance. Dissimilar metal welds between a super austenitic stainless steel (AL-6XN) and two Ni base alloys (IN625 and IN622) were characterised with respect to their dilution levels and microsegregation patterns. Single pass welds were produced over the entire dilution range using the gas tungsten arc welding process. Microstructural characterisation of the welds was conducted using light optical microscopy, scanning electron microscopy, and quantitative image analysis. Bulk and local chemical compositions were obtained through electron probe microanalysis. The quantitative chemical information w...

Arnold R. Marder

Papers

The metallurgy of zinc-coated steel

Thermal efficiency of arc welding processes

Phase transformations in ferrous alloys

Solidification of nb-bearing superalloys : Part I. Reaction sequences

Dilution and microsegregation in dissimilar metal welds between super austenitic stainless steel and nickel base alloys