Deformation behavior of laser welds in high temperature oxidation resistant Fe–Cr–Al alloys for fuel cladding applications

High gamma prime superalloy is known for its high susceptibility to welding cracking. However, for these alloys a fusion welding or deposition of crack-free is always expected for repair and refurbishment of their components. On the other hand, electro-spark deposition, though not a new process, microstructural morphology of electro-spark deposited alloy is yet a question of the hour. In this paper, thick deposition layer of a high gamma prime superalloy free from cracking was obtained and its microstructural growth characteristic was investigated. The result shows that countless single-pulse deposition spots randomly overlap with each other to make up the thick deposition layer. Grains grow vertically passing through layers and form long columnar grains with a preferential growth orientation along the build-up direction. The microstructural morphology of the deposited layers shows growing characteristics of cellular structure. (c) 2006 Published by Elsevier B.V.

Microstructural morphology of electrospark deposition layer of a high gamma prime superalloy

The investigation of the formation mechanism of the rotating-type electrospark deposition (ESD) was presented, based on studying the single-pulse electrospark deposition spot. Four different substrate/electrode couples were selected to produce single-pulse deposition spots. The similar morphology of the spots and element migration tendency were detected. A heuristic physical model was established to interpret this deposition process. The concept of “gush and splash effect” was originally proposed and proved as the dominant factor in the formation mechanism of the single-pulse electrospark deposition spot. In addition, the rotation behavior of the electrode was identified to impact on the formation of the single-pulse deposition spot.

The formation of a single-pulse electrospark deposition spot

Structural and interfacial analysis of WC92--Co8 coating deposited on titanium alloy by electrospark deposition

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Handbook of the Materials Properties of FeCrAl Alloys For Nuclear Power Production Applications

In the electrospark deposition of a material, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. When the electrode is moved away from the surface, an arc is formed momentarily, causing melting of the electrode surface for a short time. In the present work, the process was monitored in real time using a high speed camera, permitting determination of the mode of mass transfer from the electrode to the substrate, the number and size of droplets, and arc guidance (i.e. spark guidance in the present process) during deposition. The variations of welding current, welding voltage, and pulse frequency were analysed using a high performance oscilloscope. One of the applications of the process is the deposition of hard layers on die casting tools for aluminium. The analysis was carried out using a scanning electron microscope and an X-ray diffraction microanalyser. Energy input was also studied.

Processes and properties of deposits in electrospark deposition

The paper treats welding of heat-resistant ferritic stainless steels alloyed with approximately 20% Cr and 5% Al. The major part of the paper is dedicated to welding of 20%Cr-5%Al steel with 3 mm in thickness. Welding was carried out with five different welding processes, i. e., manual metal-arc, MIG, TIG, plasma arc, and laser beam welding processes, using a filler material and using no filler material, respectively. The welded joints obtained were subjected to mechanical tests and the analysis of microstructure in the weld metal and the transition zone. The investigations conducted showed that heat-resistant ferritic stainless 20% Cr-5% Al steel can be welded with fusion welding processes using a Ni-based filler material.

Welding of heat-resistant 20 % Cr - 5 % Al steels

The electrospark deposition is a process for surfacing of hard metal alloys, e.g. carbides and stellites, on the surfaces of new or old machine elements. In this process, a high current is conducted through an oscillating electrode and a substrate for a very short period of time. In the paper, the process is described and the thickness of deposited layer, chemical composition, dilution rate and the layer roughness are determined.

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Electrospark deposition for die repair

The paper deals with some characteristics of electrospark deposition. A relevant device and the process are described, the material transfer is shown schematically, and the average droplet...

Some characteristics of electrospark deposition

The paper deals with modelling of the shape and size of a crystal grain in a butt joint of ferritic high-alloy stainless steel made by TIG welding without the addition of filler material. The optimum, maximum, and minimum current intensities and welding speeds were experimentally determined. The welding speed is mathematically described as a function of the welding-current intensity. On the basis of macro specimens taken from three different directions with regard to the welding direction, the grain shape, size and location in the weld with regard to the welding direction were established. Individual characteristic crystal grains are shown in space. The average grain size was determined and described mathematically as a function of the welding parameters.

Janez Tušek

Papers

Processes and properties of deposits in electrospark deposition

Welding of heat-resistant 20 % Cr - 5 % Al steels

Electrospark deposition for die repair

Some characteristics of electrospark deposition

Geometrical Modelling of a Crystal Grain in a Weld of Ferritic Stainless Steel