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Since 1970s repair of blades of high-pressure turbines (HPT) in MOTOR SICH (reconditioning of worn edges and side walls of flanges of shroud platforms) has been performed by argon-arc surfacing process [1]. Note that our enterprise has been a pioneer in the USSR in repair of aviation blades from high-temperature nickel alloys, which at that time were regarded as absolutely unweldable. For a long time, this technology allowed performing batch-repair of such parts for a number of gas turbine engines [2]. In connection with increase of working temperature and service life on aviation engines, which were introduced comparatively recently (D18T, D436, AI222, AI450), HPT blades for operation at temperatures above 1000 °C began to be manufactured from higher alloyed hightemperature nickel alloys such as JS32-VI, JS26VI [3—5]. At operating time of more than 6,000 h, thermal fatigue cracks of up to 6 mm depth were found on blades sent in for repair, in addition to operating wear of tips and side walls of shroud platforms. Argon-arc surfacing technology and consumable materials, available for this process, do not provide heat resistance properties of reconditioned surface, required for blade operation. Greater wear and, hence, deposited metal mass increased the hot cracking susceptibility at reconditioning by argon-arc process of these blades from modern complex-alloyed high-temperature nickel alloys (with more than 60 % γ′phase content). The objective of this work is description of the features of development of surfacing technology, which allows increasing the repairability and extending the service life of HPT blades (with operating time of more than 6,000 h) from high-temperature nickel alloys JS32-VI and JS26-VI. The main goals set by repair production for such a technology, were as follows: • reconditioning of damaged blade sections after operation (shroud platforms, labyrinth seal edges, Z-shaped profiles and airfoil edges) on high-temperature alloys JS32-VI, JS26-VI, JS6K-VI and JS6U-VI, using filler material equivalent to base metal; • improvement of surfacing technology through application of a constricted-arc source with precision adjustment of welding current and filler feed mechanization, that would enable surfacing performance with limited penetration depth, and mixing of deposited metal with base metal, respectively. At that moment, PWI and SE «Ivchenko Progress» had experience of successfully solving this task. Special equipment was developed, and technology of microplasma powder surfacing (MPS) was introduced into production for reconditioning HPT blades from JS32-VI alloy for D18T engine [6]. Figure 1 shows the MPS block diagram. Deposition material in powder form is supplied by carrier gas into microplasma arc column, formed in argon atmosphere by plasma-forming nozzle channel. Heating in arc column, the powder is transferred into the weld pool, formed un© P.D. ZHEMANYUK, I.A. PETRIK and S.L. CHIGILEJCHIK, 2015

the paton welding journal

Experience of introduction of the technology of reconditioning microplasma powder surfacing at repair of high-pressure turbine blades in batch production