PSI - Issue 57

Nicolau I. Morar et al. / Procedia Structural Integrity 57 (2024) 625–632 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 1. Effects of three different laser irradiances on the residual stress depth profile of CMSX-4® laser peened samples and SP sample. The insert plot adds the shot peening result and shows a magnified view of the shallow shot peening depth contrasting the deeper plastic penetration of the laser peening The residual eigenstress profiles in Fig. 2 indicate that the stress relaxation following thermal exposure significantly reduced residual eigenstress depth profile on both LP 7-18-4 and LP+TME 7-18-4 conditions after 300hrs at 700oC, from -1039 MPa to -399 MPa and -1196 MPa to 711 MPa respectively. Despite relaxation, the compressive eigenstress depths are similar to pre-thermal exposure, extending around 5.0 mm beneath the laser treated surface and the LP+TME processing shows superior stress retention near the surface. This is somewhat to be expected as the relaxation is a diffusion process propagating in from the surface. The time history of stress relaxation for times exceeding thousands of hours will be of importance for practical applications and a topic of further study.

Fig. 2. Eigenstress depth profile of CMSX-4 laser peened specimens before and after thermal exposure at 700°C for 300 hrs.