Pulsed laser polishing of selective laser melted aluminium alloy parts

Research output: Contribution to journalArticlepeer-review

Authors

  • Debajyoti Bhaduri
  • Tina Ghara
  • Soumitra Paul
  • Catalin Pruncu
  • David Morgan

Colleges, School and Institutes

External organisations

  • Indian Institute of Technology
  • Cardiff University
  • Imperial College London

Abstract

Laser polishing (LP) of aluminium alloys by re-melting is particularly challenging due to their high thermal conductivity, diffusivity and reflectivity. In this research, a novel LP strategy is proposed to improve material’s re-melting by introducing a thermally insulating ceramic baseplate during nanosecond-pulsed laser polishing of selective laser melted (SLM) AlSi10Mg parts in atmospheric and argon environments. The strategy considerably improves the material’s re-melting as realised via sub-surface temperature measurements. This leads to a substantial reduction in the average roughness Sa (by ~80-88%) and neutral/compressive residual stresses (up to −19 MPa) when polishing in air with a laser energy density of 12 J/cm2 and 10 scanning passes. In contrast, the unpolished SLM counterparts exhibit tensile stresses, up to +55 MPa. Laser polishing, however, somewhat reduces the Al parts’ bulk hardnesses (by ~15-25%) compared to the as-built specimens. Heat affected zones (HAZ) in the form of Al-rich white layers up to a depth of ~35 μm beneath the LP surfaces are observed on the cross-sectional microstructures. The study reveals the importance of controlling the heat dissipation from the objects when laser polishing of thermally conductive materials to achieve the desired surface integrity properties.

Details

Original languageEnglish
Article number149887
Number of pages10
JournalApplied Surface Science
Volume558
Early online date25 Apr 2021
Publication statusPublished - 30 Aug 2021

Keywords

  • Laser polishing, Aluminium, Selective laser melting, Surface roughness, Residual stress, Microhardness