Laser powder bed fusion of high-strength nickel-based metal matrix composites: microstructure characterisation, mechanical testing and numerical modelling

Shu, Chang (2025). Laser powder bed fusion of high-strength nickel-based metal matrix composites: microstructure characterisation, mechanical testing and numerical modelling. University of Birmingham. Ph.D.

Preview

Shu2025PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (11MB) | Preview

Abstract

The development of high-performance nickel-based composites for aerospace and energy applications is hindered by the high crack sensitivity of IN738LC alloy, despite its excellent high-temperature durability, corrosion resistance, and fatigue resistance. To address this challenge, this study investigates the incorporation of Titanium Carbide (TiC) nanoparticles to enhance the mechanical properties and crack resistance of IN738LC fabricated via laser powder bed fusion (L-PBF). Two nanoparticle integration methods, mechanical mixing and wet chemical processing—were investigated, with the latter exhibiting superior powder morphology, nanoparticle distribution, and enhanced mechanical performance. The effects of processing parameters on porosity, microstructure, and mechanical properties were systematically analysed through a full-factorial experimental design. The optimal processing parameters were identified. The results demonstrated that TiC reinforcement significantly enhances the mechanical properties of IN738LC. Microstructural analysis confirmed that the chemically processed powders resulted in a more uniform and equiaxed grain structure, mitigating microstructural defects and improving mechanical performance. Morphological analysis of fractured samples revealed the presence of dimples, highlighting enhanced ductility. The primary strengthening mechanisms responsible for the observed improvements include fine grain strengthening, load-bearing strengthening, and Orowan strengthening. Additionally, high-fidelity Computational Fluid Dynamics (CFD) modelling was employed to investigate the influence of powder morphology on melt pool dynamics, validating the role of powder sphericity in microstructural integrity and mechanical performance. This study provides critical insights into the fabrication of high-strength, crack-resistant nickel-based composites through L-PBF, offering an experimental reference for optimizing processing parameters and nanoparticle addition methods for aerospace and energy applications.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):