Features of the technology of batch repair of blades for high pressure turbines of aviation engines applied at company «MOTOR SICH», equipment, technique and technology of microplasma surfacing, surfacing consumables and heat treatment are considered. The main types of reconditioned parts are presented, and an example of metal microstructure in repair zone is given. 7 Ref., 1 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, JS26-VI [3][4][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. De...
In current work, peculiarities of the micro-plasma powder welding deposition process applied to the batch refurbishment of D-18T aircraft engine HPT blades made of ZhS32-VI nickel superalloy with limited weldability have been studied. It has been demonstrated that extending operating resource over 6-8 thousand hours leads to an increase in ZhS32-VI “base-deposited metal” weld’s cracking susceptibility during welding and subsequent thermal processing operations. It has been shown that providing stable forming of deposited bead on the shroud edge’s surface requires applying nonstationary impulse modes of straight polarity welding current. Considering the significant amount of technological parameters of the process studied, subjective analysis of such welding modes is extremely complicated. We have introduced the method of specifying requirements for such single-layer micro-plasma powder welding deposition modes with welding current in a range of 7-20 A according to the criteria of effective arc heating power and heat input, which involves using the system for registration and digital processing of welding current-welding bead deposition time dependency. Based on the analysis of statistical data on the quantitative evaluation of cracking susceptibility of the investigated weld, the optimal range of average values has been discovered for these generalized welding deposition mode parameters to be applied in a manual or automated process, which provides no more than several percent of cracked blades detected at the end of refurbishment technological cycle. We have shown that significant technological parameters, which affect the amount of technological defects during mentioned blades’ refurbishment, are the average value of effective welding current and ZhS32 superalloy powder quality, primarily determined by oxygen and nitrogen average weight content in its dispersed particles. It was also shown that the increase in average weight content of gas impurities in the filler powder, primarily oxygen, causes a significant increase in energy consumed on deposited bead formation during the micro-plasma powder deposition process. An initial quality control method for the ZhS32-VI filler powder range has been proposed. The method is based on the average weight content of oxygen and nitrogen, evaluated by reducing fusion in transporting gas flow and on evaluation criteria of effective arc heating power and heat input average values of witness sample blades’ refurbishment process and their conformity to previously defined optimal. An evaluation of future application possibilities for registration systems and deposition mode analysis in batch repair conditions of nickel superalloy aircraft parts has been introduced.
ввиду необходимости увеличения размеров восстанавливаемых наплавкой поврежденных участков кромок лопаток ави-ационных гтД из никелевых жаропрочных сплавов на высоту 5…15 мм при микроплазменной порошковой наплавке на узкую подложку менее 3 мм требуется уточнение закономерностей формообразования наплавляемого металла. Для условий соответствующей однослойной наплавки исследован диапазон изменения энергетических показателей процесса в системе «эффективная тепловая мощность дуги-погонная энергия-площадь поперечного сечения наплавленного валика» и оценена действенность технологического управления поперечным сечением наплавляемого слоя. Установлено, что в условиях огра-ниченной глубины проплавления основного металла площадь поперечного сечения наплавляемого валика наиболее эффек-тивно регулируется за счет изменения погонной энергии в диапазоне 100...1600 Дж/мм. предполагается, что установленная технологическая взаимосвязь между величиной погонной энергии, высотой и площадью поперечного сечения наплав-ляемого валика будет способствовать формированию дополнительных критериев предотвращения образования трещин в сварном соединении «основной -наплавленный металл» при восстановлении деталей авиационных двигателей из никелевых жаропрочных сплавов многослойной микроплазменной порошковой наплавкой. библиогр. 18, табл. 4, рис. 8.
It is a necessary to specify the dependencies of deposited metal shaping due to the need of 5-15 mm height increase of the dimensions of surfacing-repaired damaged areas of blade edges of aircraft GTE of high-temperature nickel alloys in microplasma bead surfacing on narrow substrate of less than 3 mm. A range of change of the process energy indices in «effective heat power of arc-heat input-cross-section area of deposited bead» system was investigated for conditions of corresponding single-layer surfacing, and effectiveness of process regulation of deposited layer cross-section was evaluated. It is determined that heat input change in 100-1600 J/mm range is the most effective regulation of cross-section area of the deposited bead under conditions of base metal limited penetration depth. It is assumed that the determined process relationship between heat input energy, height and cross-section area of the deposited bead will promote for formation of the additional criteria preventing crack formation in the «base-deposited metal» welded joint in repair of the parts of aircraft engines of high-temperature nickel alloys using multi-layer microplasma powder surfacing. 18 Ref., 4 Tables, 8 Figures. K e y w o r d s : microplasma powder surfacing, high-temperature nickel alloy and heat-resistant cobalt alloy, narrow substrate, effective heat power of arc, heat input, thermal efficiency, cross-section area of deposited bead
Technology has been developed for repairing the nozzle assembly (SA) casing in the D-18T engine by additively growing the damaged part by microplasma surfacing with a powder of EP648VI (KhN50VMTYUB-VI) alloy. Traditionally, a part with such damage was rejected. The cost of replacing a damaged part with a new one is about 200 thousand hryvnias. The article discusses the equipment and features of the growing technology using the method of microplasma multilayer surfacing. Additive growth of the cut-damaged part was carried out on a STARWELD 190 H robotic installation for microplasma powder surfacing using EP648 VI alloy powders with a 63–163 micron fraction. After growing, heat treatment (aging at 700 ºС, exposure for 16 hours), mechanical processing, and quality control of the grown part were carried out. To create an evidence base to determine the possibility of installing a repaired part on the engine, a set of studies was carried out, which included the determination of the chemical composition of samples grown using a technology similar to repair, metallographic studies, and mechanical tests. As a result, it was found that the chemical composition of the deposited metal meets the requirements of the technical specifications TU 14-1-3046-97 "Bars made of heat-resistant alloy grade KhN50VMTYUB (EP648), and the microstructure of the deposited metal after heat treatment is a γ - solid solution with the presence of carbides, carbonitrides and a small amount of γ´ phase, which corresponds to the normally heat-treated state of the EP 648 VI (KhN50VMTYUB-VI) alloy and the level of mechanical properties of the grown alloy with subsequent serial heat treatment (aging at 700 ° C, holding for 16 hours) not lower than the level of the forging used at serial production of a part. The economic effect of the introduction of this technology is shown, which is more than 100 thousand hryvnias (about 23% of the cost of a new part).
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