PhD Thesis Defense - Saghar Fooladimahani

Cemented carbides, often called hardmetals, are the backbone of industrial tools, powering everything from heavy mining drills to high-precision manufacturing. Known for their extreme hardness, their main weakness is sudden, unexpected failure caused by microscopic defects and everyday wear.

Because natural flaws are unpredictable, traditional testing methods struggle to deliver reliable answers. This doctoral thesis introduces a game-changing solution: using controlled, artificial micro-flaws, created via precision indentations and high-power lasers, to map out exactly how hardmetals resist fracture and fatigue under real-world conditions.

Key Highlights & Findings:

• Controlled Micro-Damage: Used nanosecond laser ablation and precision indents to simulate real-world impacts and cracks with mathematical consistency.

• The Cobalt Paradox: Uncovered how the soft cobalt binder plays a dual role—increasing fatigue sensitivity in crack-free material, but actively slowing down crack growth once damage starts.

• Laser-Powered Testing: Validated laser-ablated micro-notches as a faster, highly reliable alternative to traditional fracture toughness testing.

By bridging fundamental fracture mechanics and practical material design, this research provides a powerful framework for engineering safer, longer-lasting tools for demanding industrial environments.