Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.805815
Title: Supersonic Laser Deposition and LaserForge : process mechanism coating characteristics
Author: Michaux, Laurent
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2020
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
Abstract:
LaserForge is a commercial coating process, that uses a pulsed laser to deposit flat sided wire onto a substrate with minimal heat input. Supersonic Laser Deposition (SLD) is an emerging coating technology that can be used as an alternative to existing thermal spray processes. It has the benefit of low temperature, allowing the deposition of nanostructured and temperature sensitive coatings, which is not currently possible with existing thermal spray. This main aim of this work was to undertake an experimental study aimed at identifying the process mechanism used in the LaserForge process. The understanding of the process mechanism could then be applied to process improvements for SLD coatings. As part of this study the bonding mechanisms of both LaserForge and SLD were studied. Initially a laser system to enable the exploration of the LaserForge parameter space was specified and a system set up to enable investigation of LaserForge. The LaserForge process parameter space was characterised using a pulsed laser with Ti-64 on CP aluminium. Successful bonding was achieved with parameters of 10 ms pulse length, 1400 W per pulse and 0.8 mm spot diameter. The process was determined to be a form of welding-based laser cladding, a melt-based process. Following discovery that LaserForge was a melt-based process, the direction of work was changed to focus on the SLD process mechanisms. Several WC-17Co coatings were deposited as a single layer (0.5 mm thick) on carbon steel. The coating cross section morphology was characterised using an optical microscope and scanning electron microscope. A tensile pull off test was used to measure the coating adhesion, and a four-point bend test with acoustic emission was used to monitor the failure of the coating. Plastic failure of the coating was identified, and a test limited adhesion strength in excess of 70 MPa measured. The coating was shown to have a stress-to fracture of approximately 550 MPa in tension, and a reinforcement effect of approximately 100 MPa when compared to the uncoated substrate. The problems with the deposition of the coatings with SLD were investigated and characterised, with the thermal effect from the laser during deposition found to be significant. This work has characterised the mechanism behind the commercial LaserForge process and the deposition challenges of depositing WC-17Co using Supersonic Laser Deposition. The benefit of these advancements will provide guidance for the direction of future work into LaserForge, and Supersonic Laser Deposition of nanostructured and advanced materials.
Supervisor: O'Neill, William Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.805815  DOI:
Keywords: Supersonic Laser Deposition ; WC-17Co ; LaserForge ; Coating
Share: