Development in laser peening of advanced ceramics

Abstract

Laser peening is a well-known process applicable to surface treat metals and alloys in various industrial sectors. Research in the area of laser peening of ceramics is still scarce and a complete laser-ceramic interaction is still unreported. This paper focuses on laser peening of Al2O3 ceramics employed for cutting tools, armor plating, dental and biomedical implants, with a view to elucidate the unreported work. A detailed investigation was conducted with 1064nm Nd:YAG ns pulse laser to first understand the surface effects, namely: the topography, hardness, KIc and the microstructure of Al2O3 advanced ceramics. The results showed changes in surface roughness and microstructural modification after laser peening. An increase in surface hardness was found by almost 2 folds, as the diamond footprints and its flaws sizes were considerably reduced, thus, enhancing the resistance of Al2O3 to better withstand mechanical impact. This inherently led to an enhancement in the KIc by about 42%. This is attributed to an induction of compressive residual stress and phase transformation. This work is a first-step towards the development of a 3-dimentional laser peening technique to surface treat many advanced ceramic components. This work has shown that upon tailoring the laser peening parameters may directly control ceramic topography, microstructure, hardness and the KIc. This is useful for increasing the performance of ceramics particularly for demanding applications particularly where it matters. Upon successful peening of bullet proof vests could result to higher ballistic strength and resistance against higher sonic velocity, which would not only prevent serious injuries, but could also help to save lives of soldiers on the battle fields. .

Laser shock processing of polycrystalline alumina ceramics

“…Vickers indentations were made on the surface of untreated and LSP‐treated α‐Al 2 O 3 ceramics to evaluate their resistance to indentation cracking. It is observed that at a given load ( P ), the radius of radial cracks ( c ) around the Vickers indentations was significantly reduced in LSP‐treated samples (Figure B) than untreated samples (Figure A), which suggests that LSP‐treated samples have an improved resistance to the mechanical impact . Anstis et al.…”

“…Later, Shukla et al. applied LSP to alumina ceramics . Their work show that tailoring LSP parameters can increase the surface hardness of alumina by up to 100% and the fracture toughness by 42%.…”

“…It was observed that the fracture toughness modification of these ceramics was influenced by different laser wavelengths and its absorption coefficient, the beam delivery system, and the brightness of the lasers . These early studies attributed the improved mechanical properties to the compressive residual stress induced by LSP, but did not elucidate the microscale mechanistic mechanisms . The structure‐property relationship of LSP‐treated ceramics was not investigated.…”

Surface engineering alumina armour ceramics with laser shock peening

“…Nevertheless, previous work has demonstrated some improvement in certain material properties such as hardness improvement [30,42,43], fracture toughness (KIc) [44] with selected processing parameters. This research is focused on the feasibility of strengthening Al2O3 ballistic armour plates for a bulletproof vest application.…”

“…Using the LSP technology much progress has been undertaken to improve the properties of metallic materials. Those are namely, fatigue life [28 -29], fracture toughness [29,30] hardness and wear [31 -32], tensile properties [33], stress corrosion behaviour [35 -36]; residual stress [37 -38]; material microstructure respectively [39 -40], using LSP as an independent technology and recently the introduction of hybrid laser shock peening [41].…”