Surface enhancement, by shot peening or laser shock peening (LSP), improves the fatigue life of monolithic nickel-base superalloy turbine engine components by inducing a compressive surface layer. LSP achieves deep compression with low cold work, resistance to thermal relaxation, and superior fatigue life, but is expensive, and difficult to perform. Low plasticity burnishing (LPB) produces compression, cold work, and resistance to thermal relaxation comparable to LSP. LPB is rapid, inexpensive, and easily adapted to existing machine tools. The feasibility of LPB surface enhancement of superalloys turbine engine components will be established in Phase I. Residual stress and cold work distributions will be measured before and after exposure to engine temperatures. High cycle fatigue life and thermal relaxation will be compared to shot peening and LSP. Tool life and processing costs will be established. LPB will be demonstrated on NASA superalloys. Successful completion of Phase I will provide a low-cost alternative to LSP for fatigue life enhancement which will be developed for specific applications in Phase II.
