Improving the efficiency of finishing-hardening treatment of gas turbine engine blades

Abstract

This paper considers the influence of the technology to finish and strengthen compressor blade tips made of EP718-ID alloy on the characteristics of the surface quality, surface layer, and bearing capacity. Taking into consideration the special role of the finishing-strengthening treatment in the formation of the quality of the surface layer, various options for blade tip processing were investigated. The blade tips were shaped by high-speed line milling. The finishing-strengthening stage of tip machining included manual polishing and ultrasonic hardening operations with steel balls in various combinations. The basic regularities have been established in the formation of the roughness of tip surfaces, the maximum height of micro-irregularities, the surface microhardness, and the propagation depth of the hardened layer, depending on the combination of finishing-strengthening machining techniques. The results of tests are given for multi-cycle fatigue of blade batches treated according to various variants of the technological process. The efficiency of polishing the surface of the tip after strengthening treatment has been established. To restore the quality characteristics of the surface layer after polishing, it is proposed to perform repeated strengthening treatment. It is shown that the use of double deformation hardening technology with intermediate polishing at the finishing-strengthening stage of blade manufacturing makes it possible to increase the endurance limit from 320 MPa to 400 MPa while increasing durability. Technology for the finishing-strengthening stage of machining blades made from nickel alloys, characterized by significant viscosity, has been devised. It is shown that based on the criteria of minimum labor intensity of machining and maximum endurance of blades, it is effective to use double deformation hardening with steel balls in an ultrasonic field with intermediate polishing.