Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties
Thesis (PhD)--Stellenbosch University, 2025.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Published: |
Stellenbosch : Stellenbosch University
2026
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613904823123968 |
|---|---|
| access_status_str | Open Access |
| author | Oyedeji, Ayodeji Nathaniel |
| author2 | Sacks, Natasha |
| author_browse | Oyedeji, Ayodeji Nathaniel Sacks, Natasha |
| author_facet | Sacks, Natasha Oyedeji, Ayodeji Nathaniel |
| author_sort | Oyedeji, Ayodeji Nathaniel |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134758 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:33.723Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134758 Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties Oyedeji, Ayodeji Nathaniel Sacks, Natasha Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering. Additive manufacturing Powder metallurgy Metallic composites Residual stresses Thesis (PhD)--Stellenbosch University, 2025. Oyedeji, A. N. 2025. Laser Powder Bed Fusion of Invar-based Metal Matrix Composites Reinforced with Ceramic Particles: Relationships Between Residual Stresses, Microstructure, and Mechanical Properties. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/65eec8e4-2381-498f-8b75-3b1ae373d41e ENGLISH ABSTRACT: Laser Powder Bed Fusion (LPBF) has emerged as an advanced additive manufacturing (AM) technique for creating complex metal matrix composites (MMCs) to enhance the properties of metallic components [1]. Invar 36 (Fe-36Ni), known for its low coefficient of thermal expansion (CTE) and thermal stability, has relatively low hardness and wear resistance, which limits its industrial applications. Reinforcing LPBF-fabricated Invar with ceramics like Titanium Carbonitride (TiCN), Titanium Carbide (TiC), and Titanium Nitride (TiN) has the potential to improve Invar’s mechanical properties and wear resistance due to their high hardness, thermal stability, and ability to act as grain refiners. However, their incorporation introduces challenges, including increased residual stresses. While thermal mismatch between the matrix and the ceramic phases is a primary contributor, other factors, such as rapid solidification, steep thermal gradients, and grain refinements, also induce residual stresses during the LPBF processing of the MMCs. To this end, this study optimised LPBF process parameters for Invar and Invar-based MMCs with 10wt% ceramic reinforcement (Invar-10wt%TiCN, Invar-10wt%TiC, and Invar-10wt%TiN) for relative density and hardness using the factorial and central composite design of experiments. The microstructures of Invar and the MMCs were characterised, while the mechanical, thermal expansion and wear properties were evaluated to assess the impact of these ceramic reinforcements. Residual stresses in the optimised materials were analysed numerically using the Inherent Strain Modelling (ISM) method and validated experimentally through non-destructive neutron diffraction (ND) measurements. The effect of a stress-relief heat treatment (SR-HT) on residual stress, relative to the wear properties of the Invar-based MMCs was determined. The findings indicate that the optimised Invar (which served as a benchmark) and the Invar-based MMCs achieved relative densities above 99%, with an increase in hardness of 71.76%, 86.47%, and 61.76% for Invar-10wt%TiCN, Invar-10wt%TiC, and Invar-10wt%TiN, respectively, relative to 170 HV10 for Invar. Microstructural analysis revealed that the incorporation of ceramics modified the microstructural properties, leading to grain size refinement from an average of 96.0 μm for Invar to 24.4 μm, 42.5 μm, and 87.5 μm for Invar-10wt%TiCN, Invar-10wt%TiC, and Invar-10wt%TiN, respectively and increased CTE. This refinement contributed to notable enhancements in mechanical performance, with ultimate tensile strength (UTS) increasing by 66%, 73%, and 38% for Invar-10wt%TiCN, Invar-10wt%TiC, and Invar-10wt%TiN, respectively, relative to the 430 MPa UTS of Invar. With the ISM residual stress analysis closely aligned with the ND validation, tribological analysis showed that compared to Invar, wear resistance increased by 36%, 60%, and 23% in Invar-10wt%TiCN, Invar-10wt%TiC, and Invar-10wt%TiN, respectively. However, SR-HT led to a 28% and 15% decline in wear resistance for Invar-10wt%TiCN and Invar-10wt%TiC due to thermal softening of the Invar matrix, while Invar-10wt%TiN exhibited a 36% increase, attributed to improved matrix-reinforcement bonding. A normalisation ranking approach showed that Invar-10wt%TiC showed a good balance of physical, microstructural, mechanical and wear properties. The study concluded by developing a conceptual framework as an integrated approach for predicting residual stresses in MMC parts fabricated via LPBF. AFRIKAANSE OPSOMMING: Laser Powder Bed Fusion (LPBF) het na vore gekom as 'n gevorderde toevoeging vervaardiging (AM) tegniek vir die skep van komplekse metaal matriks komposiete (MMCs) om die eienskappe van metaal komponente te verbeter [1]. Invar 36 (Fe-36Ni), bekend vir sy lae termiese uitsettingskoëffisiënt (CTE) en termiese stabiliteit, het relatief lae hardheid en slytweerstand, wat sy industriële toepassings beperk. Versterking van LPBF-vervaardigde Invar met keramiek soos Titanium Carbonitride (TiCN), Titanium Carbide (TiC), en Titanium Nitride (TiN) het die potensiaal om Invar se meganiese eienskappe te verbeter en weerstand te dra as gevolg van hul hoë hardheid, termiese stabiliteit en vermoë om as graanraffineerders op te tree. Hul inlywing stel egter uitdagings in, insluitend verhoogde oorblywende spanning. Terwyl termiese wanverhouding tussen die matriks en die keramiekfases 'n primêre bydraer is, veroorsaak ander faktore, soos vinnige stolling, steil termiese gradiënte en graanverfynings, ook oorblywende spanning tydens die LPBF-verwerking van die MMC's. Vir hierdie doel het hierdie studie LPBF-prosesparameters vir Invar- en Invar-gebaseerde MMC's geoptimaliseer met 10wt% keramiekversterking (Invar-10wt%TiCN, Invar-10wt%TiC, en Invar-10wt%TiN) vir relatiewe digtheid en hardheid deur die faktoriale en sentrale saamgestelde ontwerp van eksperimente te gebruik. Die mikrostrukture van Invar en die MMC's is gekenmerk, terwyl die meganiese, termiese uitsetting en slytasie-eienskappe geëvalueer is om die impak van hierdie keramiekversterkings te bepaal. Residuele spanning in die geoptimaliseerde materiale is numeries ontleed deur die Inherent Strain Modeling (ISM) metode te gebruik en eksperimenteel bekragtig deur nie-vernietigende neutrondiffraksie (ND) metings. Die effek van 'n stresverligting-hittebehandeling (SR-HT) op oorblywende spanning, relatief tot die slytasie-eienskappe van die Invar-gebaseerde MMC's, is bepaal. Die bevindinge dui daarop dat die geoptimaliseerde Invar (wat as 'n maatstaf gedien het) en die Invar-gebaseerde MMC's relatiewe digthede bo 99% behaal het, met 'n toename in hardheid van 71,76%, 86,47% en 61,76% vir Invar-10wt%TiCN, Invar-10wt%TiC, en Invar-10wt%TiN, onderskeidelik, relatief tot 170 HV10 vir Invar. Mikrostrukturele analise het aan die lig gebring dat die inkorporering van keramiek die mikrostrukturele eienskappe verander het, wat gelei het tot korrelgrootteverfyning van 'n gemiddeld van 96,0 μm vir Invar tot 24,4 μm, 42,5 μm en 87,5 μm vir Invar-10wt%TiCN, Invar-10wt%TiC, en Invar-10wt%TiN, onderskeidelik en verhoogde CTE. Hierdie verfyning het bygedra tot noemenswaardige verbeterings in meganiese werkverrigting, met uiteindelike treksterkte (UTS) wat met onderskeidelik 66%, 73% en 38% vir Invar-10wt%TiCN, Invar-10wt%TiC en Invar-10wt%TiN toegeneem het, relatief tot die 430 MPA UTS van Invar. Met die ISM-residuele stresanalise wat nou in lyn is met die ND-validering, het tribologiese analise getoon dat in vergelyking met Invar, slytweerstand met onderskeidelik 36%, 60% en 23% in Invar-10wt%TiCN, Invar-10wt%TiC en Invar-10wt%TiN toegeneem het. SR-HT het egter gelei tot 'n afname van 28% en 15% in slytasieweerstand vir Invar-10wt%TiCN en Invar-10wt%TiC as gevolg van termiese versagting van die Invar-matriks, terwyl Invar-10wt%TiN 'n toename van 36% getoon het, toegeskryf aan verbeterde matriksversterkingsbinding. ’n Normaliseringsrangordebenadering het getoon dat Invar-10wt%TiC ’n goeie balans van fisiese, mikrostrukturele, meganiese en slytasie-eienskappe getoon het. Die studie is afgesluit deur 'n konseptuele raamwerk te ontwikkel as 'n geïntegreerde benadering vir die voorspelling van oorblywende spanning in MMC-dele wat via LPBF vervaardig is. Doctoral 2026-01-07T07:28:25Z 2026-01-07T07:28:25Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134758 Stellenbosch University xxxi, 280 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Additive manufacturing Powder metallurgy Metallic composites Residual stresses Oyedeji, Ayodeji Nathaniel Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title | Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title_full | Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title_fullStr | Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title_full_unstemmed | Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title_short | Laser powder bed fusion of invar-based metal matrix composites reinforced with ceramic particles: relationships between residual stresses, microstructure, and mechanical properties |
| title_sort | laser powder bed fusion of invar based metal matrix composites reinforced with ceramic particles relationships between residual stresses microstructure and mechanical properties |
| topic | Additive manufacturing Powder metallurgy Metallic composites Residual stresses |
| url | https://scholar.sun.ac.za/handle/10019.1/134758 |
| work_keys_str_mv | AT oyedejiayodejinathaniel laserpowderbedfusionofinvarbasedmetalmatrixcompositesreinforcedwithceramicparticlesrelationshipsbetweenresidualstressesmicrostructureandmechanicalproperties |