Cermet composition and properties: most cermets designed for high thermal conductivity and strong thermal-shock resistance are typically composed of what approximate percentages of ceramic and metallic constituents (ceramic % followed by metal %)?

Introduction / Context:
Cermets are composite materials combining ceramic phases (for hardness, wear and oxidation resistance) with metallic binders (for toughness, thermal conductivity, and thermal-shock resistance). Many engineering exam questions test your recall of the typical ceramic-to-metal ratio used in well-known cermet families employed in cutting tools, furnace components, and high-temperature wear parts.

Given Data / Assumptions:

• The question refers to “most cermets” optimized for high thermal conductivity and thermal-shock resistance.
• We consider classical ceramic–metal combinations such as TiC/Ni, TiC/Co, WC/Co-type families identified broadly as cermets in industrial practice.
• Percentages are by volume or weight in typical textbook references; the exam expects the well-known nominal split.

Concept / Approach:
In many cermets, ceramics provide hardness, hot strength, and chemical stability, while a modest metallic fraction supplies toughness, some ductility, and heat conduction paths. A frequently cited composition window is ceramic-rich, around 70–85% ceramic with 15–30% metal binder. The widely taught nominal figure is about 80% ceramic and 20% metal for balanced cutting and thermal-shock performance. This achieves the benefits of the ceramic matrix while preserving enough metallic binder for crack bridging and thermal-stress relief.

Step-by-Step Solution:
Identify the target property set: high thermal conductivity + high thermal-shock resistance.Recall that ceramics dominate the structure for hardness; metal binder is present but limited.Typical reference compositions cluster near 80% ceramic : 20% metal.Select the option that matches this canonical split: 80 and 20.

Verification / Alternative check:
Materials handbooks and tooling catalogs show many cermet grades in the vicinity of 70–85% ceramic phase with the rest as metallic binder. The 80/20 figure is the standard “textbook memory” value targeted by this MCQ.

Why Other Options Are Wrong:

• 20 and 80: metal-dominant composite, no longer the typical cermet balance taught for this property set.
• 50 and 50 or 60 and 40: higher metal fractions generally increase toughness but reduce ceramic-controlled high-temperature hardness and wear behavior.
• 70 and 30: plausible in some systems but the classic exam answer for “most cermets” is 80/20.

Common Pitfalls:
Assuming more metal always improves shock resistance without considering loss of high-temperature performance; equating cermets with metal-matrix composites rather than ceramic-matrix composites with a metal binder.

Final Answer:
80 and 20