Surface property modifications of silicon carbide ceramic following laser shock peening

Abstract

This paper is focused on Laser shock peening (LSP) of silicon carbide (SiC) advanced ceramic. A comprehensive study was undertaken using a pulsed Nd:YAG laser. Surface modifications were investigated, particularly: the roughness, hardness, fracture toughness, microstructure, phase transformation and residual stress induced before and after the LSP surface treatment. The findings showed increase in the surface roughness, changes to the surface morphology, improved hardness, and a reduction in the fracture lengths. The LSP surface treatment also improved the surface fracture toughness from an average of 2.32MPam1/2 to an average of 3.29MPam1/2. This was attributed to the surface integrity and the induced compressive residual stress as a maximum of −92MPa was measured compared to an average of +101MPa on the as-received SiC. A slight change in the surface chemistry was also observed from the XPS spectra, however, no real phase transformation was seen from the X-ray diffraction analysis. Laser energy density of around 1.057J/cm2, 8.5mm spot size, 10Hz pulse repetition rate (PRR) at 6ns pulse duration, and 1064nm wavelength resulted to obtaining a crack-free surface treatment and demonstrated that the technique is also beneficial to enhance some of the properties to strengthen brittle ceramics such as SiC.