Repair surfacing of gas turbine engine blades from high-temperature nickel alloys with surface defects and damage

Abstract

Cored wires are used in numerous welding processes with or without external gas or flux shielding. Submerged arc welding (SAW) with cored wires, seamed or seamless, for joining mild and low alloyed steel grades is a technique that has demonstrated clear advantages during the three last decades. Ever since its invention, the SAW process has evolved with one main goal: to combine quality with productivity. With low alloy wires, the benefits have already been clearly demonstrated and widely exploited. However, little has been written on SAW and cladding with cored wires for corrosion or heat resisting applications. Its extension to high alloy compositions brings corresponding benefits and adds some specific and unique features. This paper focuses on consumable specificities and on the quality and productivity features of SAW with CRA (corrosion resistant alloy) cored wires. It describes the potential as well as the limitations of this technique. Cored wires are now used for submerged arc welding of almost all stainless steels ranging from soft martensitic to super-duplex, and for a series of nickel base compositions as well as for cladding cobalt base alloys. Examples of industrial applications with austenitic, duplex, martensitic and heat resisting stainless steels are given to illustrate the potential of the cored wire solution. 13 Ref., 4 Tables , 25 Figures.

Features of the Microstructure of Welded Joints of Single Crystals of Heat-Resistant Nickel Alloys

“…An increase in the width of iso-intensive lines in one direction, tortuosity of the formation contour, the appearance of localized asymmetric regions, an increase in reflection intensity indicate the initial stage of the formation of a multilevel dislocation structure, and an increase in the dislocation density [14,16] as a result of thermos-deformation effect of welding.…”

“…1), corresponding to the deviation of the direction of maximum heat removal from the orientation [001] by 10-15 and more degrees from the front of solidification of the weld pool. During the crystallization of this area, a structural disruption of not only the orientation, but also the temperaturetime conditions [15,16,19] of directional crystallization is observed, which leads to the formation of high-angle grain boundaries, the crystallographic orientation of which may differ from the rest of the weld metal by 35-55 degrees (Fig. 9).…”

“…And, if for the industrial growth of single crystals the optimal values of these characteristics, the methods and ways of achieving them have been sufficiently clarified, then for welded joints such data are clearly insufficient, despite the large number of publications, which are mainly devoted to the preservation of the initial crystallographic orientation by the weld metal, the formation of high-angle boundaries, grains and cracks [10][11][12][13][14][15][16].…”