Petrik I. Processes of restavration ogas turbine engine blades made of nickel and titanium-based hard -to-weld alloys by welding and brazing.

The thesis is dedicated to development of industrial production processes of restoration of highly loaded blades made of the high-strength titanium and high temperature nickel alloys used in gas flow duct of gas turbine aeroengines with the aim of extension of their service life. The thesis examines principal causes of failure of gas flow duct parts of gas turbine engines. Effect of condition of EBW, AAW, brazing, composition of filler material and heat treatment conditions on weldability of blades made of titanium and high temperature nickel alloys was investigated. Check of weldability of alloys with the use of classic circular test and Varestraint Test was performed. Unsatisfactory weldability of nickel alloys of ЖС6 type was determined, this was caused by presence of temperature range at low values of critical deformations. Method of “blade circular” test as developed for production rapid assessment of weldability of blade material was worked out. Optimum conditions of welding and brazing damaged blades ere achieved. Researches were performed for determining effect of welding conditions on distribution of stress field within blade volume. A gradient-stress model for selection of production parameters, materials and methods of treatment of welded joints was suggested, in which the determinative factor in assigning repair procedures is accepted as the generalized criterion of welding of structural materials. Based on this, a method was developed for determining zones of possible repair of GTE fan blades by welding. This makes it possible to extend them as compared to permissible zones of repair in accordance with the earlier used repair processes. Possibility of use of this model for high-temperature nickel alloys and other structural materials used for blades was reasoned. Standard documents, instructions, group production processes for repair were developed, which were coordinated with designers that developed engines. The developed processes for repair of loaded gas flow duct blades were introduced into production at Motor Sich JSC.