Effects of laser shock peening on silicon nitride ceramic with varying sintering additive ratios

Abstract

Silicon nitride ceramic (Si3N4) for industrial applications is conventionally manufactured with sintering additives, and the properties of Si3N4 change significantly based on the contents of these additives. In this study, we investigate the effects of laser shock peening (LSP) on Si3N4 sintered with varying ratios of sintering additives. The Si3N4 samples were sintered with a mixture of Y2O3, MgO, and SiO2 sintering additives at 5, 7, 9, and 11 wt%. A Nd:YAG laser (wavelength = 532 nm, maximum pulse energy = 1.4 J, repetition rate = 10 Hz, pulse duration = 8 ns, beam diameter = 11 mm, top-hat profile) was used to irradiate the Si3N4 samples. The samples were coated with a protective layer (100 μm thick aluminum foil) and a water layer to confine plasma. LSP of Si3N4 with 5 % sintering additives resulted in a slight change in surface hardness but a 77 % decrease in surface compressive residual stress. In contrast, LSP of Si3N4 with 11 % sintering additives led to a simultaneous increase in surface hardness (7.3 %) and surface compressive residual stress (67 %), indicating a significant difference in the effectiveness of LSP depending on the ratio of sintering additives. Additionally, the surface of Si3N4 with 11 % sintering additives showed evidence of grain refinement after LSP. It was demonstrated that the bending strength of Si3N4 with 11 % sintering additives increased by 15.2 %, and the depth of the fracture origin was significantly deepened. © 2024 Elsevier Ltd and Techna Group S.r.l.