Comparison of turbine blade wing of heat-resisting alloy geometry restoring techniques

Аuthors

Klimov V. G.

Samara State Technical University, SSTU, 244, Molodogvardeyskaya str., Samara, 443100, Russia

e-mail: vadim3945@yandex.ru, v.klimov@uecrus.com

Abstract

Compressors and turbines of aviation gas turbine engines are the main components that determine the engine performances. Turbine blades are the most costly elements while their production. Rejection of an unfit turbine blade usually happens due to insignificant defects and consequently, their restoring is economically sound.

This article considers the process of geometry restoring (height) of aviation turboprop engine NK-12MP turbine starters (TS) blade wing. A comparative analysis of four types of restoration has been carried out: argon-arc surfacing with filler wire ХН60ВТ; soldering with solder powder VPr24 in ceramic forms; laser surfacing with filler wire ХН60ВТ; laser surfacing in powder bath with VPr24 solder.

The furnace soldering in ceramic forms technique consists in placing the blade in a specially prepared form repeating the ceramic blade profile with the necessary allowance for further machining, with further powder solder filling. Then the soldering process in a vacuum furnace begins.

The technique of laser welding in a powder bath consists in surfacing of the blade wing placed in a bath filled with facing powder. The blade was placed in the powder fill so that its wing and the surface of the powder fill were at the same level. The laser beam worked on the tangent of the blade wing and the powder.

Based on blade restoration techniques comparative analysis I concluded that the most effective technique in this case is pulse laser surfacing. Surfacing in powder bath herewith provides higher performance compared to laser surfacing with filler wire. Laser surfacing main differences from the classical techniques of turbine blades geometry restoring are revealed. The paper presents comparative analysis of the restored layers structure by electronic microscopy with elemental analysis of transverse sections of the samples. The degree of the effect of each technique on the blade basic material was revealed. It is found that the furnace soldering and laser surfacing techniques exert least effect on the strengthening phase γ’ of the cast alloy GC-6K. The elemental analysis revealed the presence of, presumably, the grid of complex intermetallic compounds, as well as tungsten and chromium carbides in the solder structure. Microhardness (Hv) of the recovered layers and various phases of powdered solder VPr24 was determined, and the CTLEM (coefficient of thermal linear expansion of material) involved in the restoration process was measured.

Keywords:

laser surfacing, argon-arc surfacing, self- fluxing brazing alloys, powder bath, coefficient of linear expansion, restoring repair, electron microscopy, elemental analysis, micro-hardness, soldering

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