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Micro-geometrical errors, surface roughness, and surface integrity (microstructure, residual stresses, microhardness) play an important role in defining the quality of the gears as they directly affect their noise, vibration characteristics and service life during their use. In the present work, underwater laser shock peening (LSP) is employed to improve the quality of the laser powder bed fusion built 17-4 PH small-size spur gears (12 mm outside diameter). LSP was employed near the spur gear root, and effects were measured in terms of residual stresses, variation in microgeometry errors, surface roughness, porosity, microstructure, and microhardness. It was observed that LSP could impart compressive residual stresses up to 0.4 mm of measured depth, while the surface roughness has improved by 32%. Microgeometry and microhardness of gears showed minor variations. Additionally, LSP has shown an impact on the microstructure as the grain orientation was altered and grain size reduced by 15.6% due to shock wave transmission. The study paves the way to use LSP as a post-processing technique to modify the surface characteristics of LPBF-built miniature spur gears with minimal impact on the gear microgeometry.

We studied the effect of Ga3+and Sc3+ on Yb:YAG emission at cryogenic temperatures on three different mixed garnets namely Yb:YGAG, Yb:YSAG and Yb:YSGAG. The compositional tuning of these mixed garnets was achieved by preparing ceramic pellets by solid state reaction with different concentration of Ga3+, or Sc3+, or both. The incorporation of Sc3+ in Yb:YAG leads only to a limited spectral broadening. On the other hand, the incorporation of either Ga3+ or both Ga3+ and Sc3+ results in a significant spectral broadening. In the latter case, this inhomogeneous broadening is attributed to the mixed occupancy of both Ga3+ and Sc3+ in octahedral and tetragonal sites in the crystal lattice leading to a significant distortion in the structure.

This paper investigates the post-processing of additively manufactured stainless steel (SS) 304 L samples through laser shock peening (LSP). Four samples, differently processed, (i) as-built (AB); (ii) as-built + annealed; (iii) as-built + polished; and (iv) as-built + annealed + polished, were used to study the effect of LSP at pre-identified parameters to understand the mechanism and behavior of processing different conditions. In addition, compressive residual stresses and surface morphology were considered as a response to measure the effects of LSP on processed samples. The results have shown significant improvements in compressive residual stresses where the values have changed from initial tensile to compressive (−1170 MPa) and remain compressive up to the depth of 1 mm in most cases. The results of this research help better understand the LSP mechanism in the post-processing of AM Parts.