Analytical modelling and control of thermal energy and geometry in wire-fed laser cladding

Student thesis: PhD Thesis

Abstract

Laser cladding is an additive manufacturing technology. By forming a stable track on the target surface, metal can be rapidly deposited on the substrate in large quantities. It is now widely used in parts repair and net shape additive manufacturing. With the increasing popularity of automation systems in the manufacturing industry, the demand for built-in prediction and control models is more and more obvious, so that robots can complete tasks without human intervention.
In this study, the full shape of the material deposition has been analytically modelled, including the bulge (the part above the surface) and the melt pool (the part below the surface). The modelling method is based on the capillary theory to calculate the interfacial tension at the interface between the bulge and the air, the melt pool and the substrate, so that the full profiles of the deposited material can be predicted under different process parameters (such as laser power, scanning speed and wire feeding speed). In addition, the single-track cladding model is extended to overlapping tracks on horizontal surfaces to accurately predict and control geometry. The remelting and bonding behaviours were also analysed to assess the integrity of the cladding. In addition, the model is extended to take into account the cladding behaviour on the inclined surface, which creates the possibility of repairing free-form parts.
The model is validated by experimenting with various process parameters and then making appropriate measurements (the geometric shape/size of the bulge is measured by coordinate measurement machine, and the surface integrity is measured by optical microscope). The shape error of laser cladding between experiment and simulation of optimizing process parameters is acceptable and can be used in actual manufacturing. Since the model is time dependent, it can be easily implemented on any machine tool or manipulator. Using this model, the shape of the bulge and the weld pool can be precisely controlled by changing the laser scanning speed in a complex way.
This work is helpful to understand the material accumulation process in the wire-fed laser cladding process, and shows the analytical modelling method, which can be used to improve the current capability of this technology in part repair or net-shape additive manufacturing.
Date of Award15 Mar 2023
Original languageEnglish
Awarding Institution
  • The University of Nottingham
SupervisorHaonan Li (Supervisor), Dragos Axinte (Supervisor) & Zhirong Liao (Supervisor)

Keywords

  • Laser Cladding
  • Additive Manufacturing
  • Mathematical Model
  • Surface Tension
  • Laser Material Processing

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