Projecte llegit
Títol: Coated cutting tools used for machining metallic alloys: Assessment of surface integrity and mechanical properties at different length scales
Estudiants que han llegit aquest projecte:
BABIC, DANIJEL (data lectura: 10-09-2025)- Cerca aquest projecte a Bibliotècnica
BABIC, DANIJEL (data lectura: 10-09-2025)Director/a: LLANES PITARCH, LUIS MIGUEL
Departament: CEM
Títol: Coated cutting tools used for machining metallic alloys: Assessment of surface integrity and mechanical properties at different length scales
Data inici oferta: 08-01-2025 Data finalització oferta: 08-09-2025
Estudis d'assignació del projecte:
- MU AEROSPACE S&T 21
| Tipus: Individual | |
| Lloc de realització: |
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| Nom del segon director/a (UPC): Giselle Ramirez Sandoval (UPC) | |
| Departament 2n director/a: | |
| Paraules clau: | |
| Mechanical properties / coated cutting tools / CVD / cemented carbides | |
| Descripció del contingut i pla d'activitats: | |
| Coated cutting tools used for machining metallic alloys: Assessment of surface integrity and mechanical properties at different length scales
- Machining of aeronautical alloys - Surface modification technologies of cutting tools - Surface integrity and mechanical characterization at different length scales - Assessment of post-treatment effects on the mechanical integrity of coating/substrate systems To be conducted at the Dept Materials Science and Engineering in EEBE, within the framework of research group CIEFMA |
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| Overview (resum en anglès): | |
| The aerospace industry relies on "difficult to cut" materials, requesting high performance of cutting tools. For tool materials, such as cemented carbides, coating through chemical vapor deposition can improve mechanical and thermal properties. Since CVD requires high temperatures, (800C - 1200C) this process can induce residual tensile stresses and thermal cracking during cooling due to mismatching thermal expansion coefficients within the materials. To aid in reducing residual stresses, while also improving durability performance, post treatments such as shot-peening or wet blasting are often implemented.
This research aims to evaluate and characterize damage mechanisms of coated and post-treated cemented carbides cutting tools, in terms of the interaction between the thermal cracking patterns response under contact loading conditions. Specifically, this involved evaluating bi-layer coated cemented carbide inserts (WC-Co-Cr substrate with alpha-Al2O3/TiCN coatings of approximately 9 micrometer "thin" and 26 micrometer "thick" variations), subjected to various post-treatments: shot-peening (SP), wet-blasting (WB), a combination (SP+WB), and no treatment (NT). Damage was induced using a Rockwell indenter with loads ranging from 1 kg to 100 kg. The investigation occurred in three parts. First, initial pristine surface evaluation, then indentation-induced damage assessment, and finally analysis of the evolution of thermal crack network and radial cracking produced by the indentation through progressive polishing. Microscopic techniques, including Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) Spectroscopy, were used for both qualitative (HF DIN 4856 standards) and quantitative assessment. Quantitative analysis utilized ImageJ software to measure spalling area, radial crack count, longest radial crack length, average indentation depth. Finally, thermal crack networks were investigated in non-treated samples by progressively polishing the surface and observing changes at different depths. Results demonstrate distinct damage micro-mechanisms as a result of changing coating thickness and post-treatment. For non-treated samples, thermal cracking and spalling was most prominent as expected, guiding damage such as radial crack progression, with heavier loads enabling cracks to jump between thermal crack networks. A damage sequence of cracking observed was thermal, followed by circular, then radial cracking. In shot-peened samples, the post treatment process introduced residual fragmentation of the shot particles, increasing surface roughness. This led to fretting type damage, decreased radial material loss due to reduced material clumping as spalling edges became more crushed and rounded. Thermal and radial cracking often flowed around or stopped at shot-peening fragmentation features. Spalling reached shallower depths from this post-treatment type on thicker coated samples. The combined SP+WB treatment produced smoother surfaces but retained fragmentation, with material removal near cracks similar to SP. Spalling and radial cracks followed the thermal cracking network, with spalling typically limited to the TiCN layer. Wet-blasted samples showed varied and complicated responses. Thin coatings exhibited no surface spalling at 62.5 kg, with energy transferred into longer and wider radial cracks and increased material voids. Contrastly, thick coatings displayed more spalling than other types, similar to SP+WB. The surface around applied damage appeared to have more square spalling edges, following thermal cracking damage networks within the coating. Investigations into thermal crack network evolution revealed that in both non-treated thin and thick coatings, the thermal cracking network extended to the substrate. However, spalling in the thin coating reached the WC-Co substrate at lower Rockwell indentations, whereas in the thick coating, spalling extended only to the TiCN layer at 62.5 kg. |
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