ELIMINATION OF INEQUIGRANULARITY IN GAS TURBINE ENGINE COMPRESSOR BLADES BY MEANS OF INTENSIVE PLASTIC DEFORMATION

Abstract

Decrease of inequigranularity in gas turbine engine compressor blades airfoil made of ЭП718-ИД iron-nickel alloy aimed at increase of their processibillity and bearing capacity. Technique. Methods of microscopic analysis were used in order to determine grain sizes of blades airfoil after different processing methods. Method of intensive plastic deformation by means of twist extrusion was used in order to form submicrocrystalline structure. Results. It is established that inequigranularity of high pressure compressor blades structure occurs at the stage of blanks production. Subsequent thermal treatment does not eliminate the defect. In order to form favorable structure it is offered to use method of intensive plastic deformation (twist extrusion) at preliminary stage of technological process. Such deformation treatment also improves homogenization of alloying elements all over the blank section. It results in increase of the blade strength properties and decrease of their dispersion. Considering the fact that investigated alloy has low plasticity within the range of deformation temperatures, there was made analysis of conditions for impementation of intensive plastic deformation of blanks aimed at preservation of their integrity and formation of submicrocrystalline structure in them. It is established that two alternative variants of technological process of intensive deformation at high and low temperatures are possible. It is shown that from the point of view of practical implementation, it is rational to perform intensive deformation of small blanks within the low temperature range, alternating it with hardening procedure. Analysis of the combination of factors determining possibility of successful implementation of intensive plastic deformation of the blade blanks by means of twist extrusion, has  allowed to determine requirements to parameters of technological process, to the unit and initial blanks. Their fulfilment allows to implement successfully the offered blades production technology based on iron-nickel alloys with submicrocrystalline structure. It is given the design of special production unit. Scientific novelty. It is proven feasibility of application of intensive plastic deformation by means of twist extrusion of blanks made of ЭП718-ЦЦ iron-nickel alloy in order to form submicrocrystalline structure that increases degree of their subsequent deformation and excludes occurrence of inequigranularity. Practical importance. It is designed a special unit for implementation of twist extrusion of blanks under controlled conditions that allows to use intensive plastic deformation at preliminary stage of compressor blades production process. Application of blanks with uniform submicrocrystalline structure allows to reduce quantity of transitions during the blade airfoil forming by pressure, intensify the blade tool machining conditions and increase the blades bearing capacity.