Cutting Tool Coatings Explained: TiN, TiAlN, DLC, CVD Diamond and How to Choose the Right One

July 29, 2025

Cutting Tool Coatings: Key Properties and How to Choose the Right One

When it comes to improving tool life, reducing wear, and maximizing machining performance, selecting the right cutting tool coating is just as critical as choosing the tool material itself. In this guide, we break down common coatings like TiN, TiCN, TiAlN, CrN, DLC, and CVD Diamond — and share practical factors to help you make the best choice [1].

Common Coating Types and Their Properties

🟡 TiN (Titanium Nitride)

Color: Gold
Hardness: ~2500 HV
Friction: Low
Best for: General-purpose machining, mild steels, high-speed steels
Pros: Inexpensive, improves wear resistance and lubricity
Limitations: Not ideal for high-temperature or abrasive conditions

🔵 TiCN (Titanium Carbonitride)

Color: Blue-gray
Hardness: ~3000 HV
Best for: Hardened steel, cast iron, stainless
Pros: Harder than TiN; better wear resistance
Limitations: Less heat resistant than TiAlN

🟣 TiAlN / AlTiN (Titanium Aluminum Nitride)

Color: Violet or dark gray
Hardness: ~3500 HV
Best for: High-speed machining, dry cutting, aerospace alloys
Pros: Excellent heat resistance due to aluminum oxide layer
Note: AlTiN has higher Al content, better for high-temp alloys

⚪ CrN (Chromium Nitride)

Color: Silver
Friction: Very low
Best for: Applications requiring corrosion resistance (e.g., medical, food)
Pros: Excellent anti-stick, low-friction coating
Limitations: Lower hardness than TiAlN

🖤 DLC (Diamond-Like Carbon)

Color: Black
Best for: Aluminum, copper, plastics, CFRP
Pros: Extremely low friction, great for non-ferrous materials
Limitations: Poor thermal resistance; not for ferrous metals
Example: https://ky-tools.com/products/square-end-mill-long-neck-carbide-dlc-coated

💎 CVD Diamond

DColor: Silver-white
Best for: Graphite, ceramics, composites
Pros: Hardest known coating, excellent wear resistance
Limitations: Brittle and expensive, not usable on steel
Example: end-mills-for-graphite

How to Choose the Right Coating?

Choosing the right coating isn’t one-size-fits-all. Here are the six most important factors:

1️⃣ Workpiece Material

This is the most crucial factor. Different coatings react differently with:

Steel / Hardened Steel
Cast Iron
Stainless Steel
Aluminum Alloys
Titanium / Inconel / Superalloys
Composites / Graphite / Plastics

📌 Example: TiAlN performs well on stainless steel and superalloys, while DLC is ideal for aluminum.

2️⃣ Machining Type

Turning, Milling, Drilling, Threading
Continuous vs Interrupted Cutting
Impact Load Level

Roughing in cast iron may require tougher coatings like TiCN, while finishing in aluminum suits DLC.

3️⃣ Cutting Parameters

Speed, Feed, and Depth of Cut
Higher speeds generate more heat. Coatings like AlTiN offer oxidation protection at 800°C+.

4️⃣ Coolant and Lubrication

Wet, MQL (minimum quantity lubrication), Dry machining

TiAlN and AlTiN are excellent for dry machining. CrN and DLC offer better performance with lubricants.

5️⃣ Tool Substrate

The coating must adhere well to the base tool material:

Carbide, HSS, Ceramic, PCBN, etc.

CVD coatings are not suitable for high-speed steel. DLC needs a smooth, hard substrate.

6️⃣ Cost vs Performance

High-performance coatings cost more but may dramatically increase tool life and reduce downtime. Consider:

Tool cost
Tool change time
Part accuracy and surface finish
Waste reduction

Final Thoughts

The right tool coating can be the difference between success and failure in high-performance machining. Understanding your application’s material, machining method, and thermal conditions will guide you toward the ideal solution.

Shop Coated Tools at KYTOOLS

Looking for high-performance coated tools?
✅ TiSiN-coated end mills for stainless
✅ DLC-coated tools for aluminum
✅ CVD diamond-coated tools for composites
➡️ Browse our full selection here