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This study aimed to identify the optimal combination of wavelength and laser pulse density to achieve the optimal pulse pressure that can induce the maximum compressive residual stress at the subsurface of microalloyed steel. For this, laser shock peening without coating (LSPwC) was performed on microalloyed steel samples at the fundamental wavelength (1064 nm) with pulse densities of 3, 6, 9, and 12 GW/cm2 and at the second harmonic wavelength (532 nm) with pulse densities of 3, 6, and 9 GW/cm2. The residual stress distributions were studied to a depth of 500 µm in the laser-treated samples. Tensile residual stress was observed at the surface of laser-peened specimens in both wavelength conditions (1064 and 532 nm). The significant impartment of compressive residual stress across the depth was achieved at the fundamental wavelength (1064 nm). The maximum compressive residual stress was attained with a laser pulse density of 9 GW/cm2 in the 1064nm wavelength condition. The optical micrographic analysis in the subsurface regions of the LSPwC specimen at 1064 nm and 9 GW/cm2 shows evidence of a high degree of plastic deformation. Electron backscatter diffraction (EBSD) analysis shows that there is grain refinement due to plastic deformations in samples subjected to the fundamental wavelength. Microhardness distribution analysis across the subsurface region shows work-hardening effects in the laser-processed samples in the 1064 nm condition. This study also shows that there is an indication of a thermal softening effect in the samples treated with the 532 nm wavelength, and it is correlated with lower compressive residual stress across the depth.

In this study, the microstructure, high-temperature tribological performance and mechanical properties of solution-aged Ti-10V-2Fe-3Al were investigated. The microstructure of solution-aged Ti-10V-2Fe-3Al reveals a bimodal α and β microstructure with uniformly dispersed α precipitates in β matrix phase. The hot tribological performance of solution-aged Ti-10V-2Fe-3Al was investigated at different temperatures (28, 250, 350, and 450 °C) in a high-temperature pin-on-disc configuration. The wear mechanisms were evaluated at the worn-out surface using a scanning electron microscope (SEM). The abrasive wear mechanism is predominant at 28 °C and 250 °C testing conditions, whereas the oxidation and delamination are dominant wear mechanism at 350 °C and 450 °C testing conditions. The worn-out surface at different temperature conditions was characterized by X-ray diffraction (XRD) and energy dispersive x-ray spectrometer (EDS) analysis. The absence of protective oxide formation at 28 °C and intermittent protective oxide formation at 250 °C testing condition is ineffective in protecting the surface from wear damages and high wear loss. The protective tribo-oxide formations at 350 °C and 450 °C is continuous and provide improved wear resistance behavior of the material. The V2O5 rich tribo-oxide layer formation at 350 °C offers excellent wear resistance and protection against wear damages among the testing conditions. The Vickers microhardness study of the samples tested at different temperature conditions shows significant differences in the hardness magnitude at the cross-section.

The failure of turbine blades due to solid particle erosion is a serious concern in aviation applications. This research investigates the solid particle erosion behaviour of laser powder bed fused IN718 alloy for the effect of temperature (400°C, 500°C and 600°C) and impact angle (45° and 90°) in a gas-jet erosion setup. The erosion rate progressively increased with the test temperature and it is significantly higher in the 45° eroded samples. The eroded samples were characterized for residual stress distribution, surface topography and surface roughness using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and 3D optical profilometer. Compressive residual stress is evident in all eroded samples, and higher residual stress is measured in the 90° eroded samples. Ploughing, crater lip formation and cracking are the erosion features observed in 45° eroded samples. In comparison, localized plastic deformation, platelet mechanisms and cracked ridges are observed in 90° eroded samples. Crack formation at 600°C test condition is attributed to severe erosion degradation in both the impact angles (45° and 90°). The as-printed and solution-double aged samples were thoroughly investigated for microstructure and microhardness distribution at the region parallel and perpendicular to the build direction.

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