Hardening methods influence on fatigue strength of the compressor blades with stress concentrators

The paper analyzes the influence of different hardening methods on fatigue strength of the gas turbine engine compressor blades made of titanium alloy with stress concentrators. The 5 mm wide blade feather edge zones were hardened using the laser shock peening (LSP, LSPwC) and low-plasticity smoothing methods. The solid-state Nd:YAG laser was used to harden the blades on both sides by the LSP method. The 80 ?m thick aluminum foil was used as the protective layer. Low-plasticity smoothing was performed using a hydrostatic tool on the CNC machine. Endurance limits were determined for blades without hardening (serial) and with hardening, as well as for blades of both groups with applied stress concentrators (damage imitation) such as a nick of different depth on the leading edge. The paper states that the blade leading edge machining by different hardening methods reduces the effective stress concentration factor by 1.2–2.0 times relative to that of blades without hardening. Fracture analysis after hardening shows that the hardened layer depth could be 0.6…1.0 mm. Destruction after hardening becomes sublayer, the crack development source coincides with the zones merger boundary during hardening on both sides. The paper shows that nicks about 0.5 mm deep almost do not reduce fatigue properties of the hardened blades in the stress concentration zone. Introduction of the laser shock peening would reduce the number of blade stripping and premature removal of the gas turbine engine.
EDN: QTMYIH, https://elibrary/qtmyih

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