Feasibility study of microscale laser shock processing without absorbing coating to improve high-cycle fatigue performance of DZ17G directionally solidified superalloy

A kind of turbine blade in an aero-engine, made of DZ17G directionally solidified superalloys, often fractured at the tenon tooth root. Microscale laser shock processing (LSP) without absorbing coating (microscale LSPwC) under water was suggested to improve its high-cycle fatigue performance. In this paper, a DZ17G superalloy simulated-blade was designed and treated by microscale LSPwC with different impacts. Surface microhardness was improved from 410 to 502 HV with a 70 μm thick hardened layer post one LSP impact, and increasing LSP impact could improve the depth of hardened layer effectively. There was no new phase formed and grain refinement, only with high-density dislocations generated. The density of dislocations on section decreased sharply with depth. The fatigue limit of DZ17G superalloy simulated-blade was improved from 253.14 to 301.14 MPa, and there was still a fatigue strength improvement of 9.0% after insulation treatment under 800 °C for 2 h.A kind of turbine blade in an aero-engine, made of DZ17G directionally solidified superalloys, often fractured at the tenon tooth root. Microscale laser shock processing (LSP) without absorbing coating (microscale LSPwC) under water was suggested to improve its high-cycle fatigue performance. In this paper, a DZ17G superalloy simulated-blade was designed and treated by microscale LSPwC with different impacts. Surface microhardness was improved from 410 to 502 HV with a 70 μm thick hardened layer post one LSP impact, and increasing LSP impact could improve the depth of hardened layer effectively. There was no new phase formed and grain refinement, only with high-density dislocations generated. The density of dislocations on section decreased sharply with depth. The fatigue limit of DZ17G superalloy simulated-blade was improved from 253.14 to 301.14 MPa, and there was still a fatigue strength improvement of 9.0% after insulation treatment under 800 °C for 2 h.