TiAlN for stainless and high-speed work. TiN for basic steel. AlCrN for titanium and superalloys. TiCN for medium-speed stainless. That's the decision tree — this guide explains why and when each coating wins.
Carbide tool coatings extend tool life by 2–10x by adding a thin layer (2–6 microns) of heat-resistant, friction-reducing material to the cutting surface. The coating you choose depends on workpiece material, cutting speed, and whether you're using coolant. Get it right and tool costs drop. Get it wrong and you're replacing inserts every few parts.
Carbide inserts with various coatings — each coating color indicates different material composition and heat resistance
The Five Coatings That Matter
| Coating | Color | Max Temp | Hardness (HV) | Friction | Best For |
|---|---|---|---|---|---|
| TiN | Gold | 600°C | 2,300 | Medium | Mild steel, low speed, general purpose |
| TiCN | Blue-gray | 750°C | 3,000 | Low | Medium-speed steel, light stainless, abrasive materials |
| TiAlN | Dark violet | 900°C | 3,300 | Low | Stainless, high-speed steel, cast iron, dry machining |
| AlTiN | Black | 950°C | 3,500 | Very low | High-speed finishing, hardened steel, dry cutting |
| AlCrN | Silver-gray | 1,100°C | 3,200 | Very low | Titanium, superalloys, extreme heat applications |
TiN (Titanium Nitride) — The Gold Standard Baseline
TiN is the original and most common carbide coating. It's the gold-colored layer you see on most standard inserts. At 2–4 microns thick, it adds modest hardness and reduces friction at the chip-tool interface.
Strengths: Cheapest coating option. Works well on mild and medium carbon steel at moderate speeds (150–250 m/min). Good for general-purpose turning, drilling, and milling where temperatures stay below 600°C.
Weaknesses: Breaks down rapidly above 600°C. Completely inadequate for stainless steel, titanium, or any high-speed application. If your insert turns dark brown or loses its gold color, TiN has failed.
When to use: Budget operations on mild steel. Drill bits for general-purpose work. Low-speed applications where coating cost matters more than performance.
TiCN (Titanium Carbonitride) — The Step Up
TiCN adds carbon to the TiN formula, increasing hardness by 30% and heat resistance to 750°C. It's the blue-gray coating that bridges basic and performance-grade inserts.
Strengths: Better wear resistance than TiN. Good on medium-carbon steel, cast iron, and abrasive materials. Lower friction coefficient means cleaner chip flow. Works for light stainless work at reduced speeds.
Weaknesses: Still not adequate for high-speed stainless or dry machining. The carbon content makes it slightly more brittle than TiN — don't use on heavy interrupted cuts.
When to use: Upgraded alternative to TiN for steel. Cast iron machining. Abrasive materials like high-silicon aluminum alloys. Stainless finishing at low speed only.
WNMG carbide inserts — available in multiple coating options for different material requirements
TiAlN (Titanium Aluminum Nitride) — The Performance Standard
TiAlN is the most important coating in modern machining. The aluminum content forms a protective aluminum oxide layer at high temperatures, which actually improves performance as the tool gets hotter. This self-healing property makes it the default for any demanding application.
Strengths: Handles temperatures up to 900°C. Ideal for stainless steel, high-speed steel cutting, and dry machining. The aluminum oxide barrier reduces heat transfer to the carbide substrate, extending tool life 3–5x compared to TiN. Works with and without coolant.
Weaknesses: More expensive than TiN/TiCN (typically 30–50% premium). Slightly less effective at very low speeds where the self-healing aluminum oxide layer doesn't form. Not the best choice for aluminum workpieces — the aluminum-on-aluminum contact promotes built-up edge.
When to use: All stainless steel work. High-speed steel and cast iron. Dry machining or minimal coolant. Any application above 200 m/min surface speed. This should be your default coating unless you have a specific reason to use something else.
AlTiN (Aluminum Titanium Nitride) — Maximum Heat Resistance
AlTiN reverses the ratio — more aluminum, less titanium. This pushes heat resistance to 950°C and creates an even thicker aluminum oxide barrier. It's the premium version of TiAlN for the most demanding conditions.
Strengths: Highest heat resistance of the standard coatings (short of AlCrN). Exceptional for high-speed finishing where cutting temperatures peak. Best coating for hardened steel (HRC 45–62). Excellent dry machining performance.
Weaknesses: More brittle than TiAlN — not ideal for heavy interrupted cuts. Premium price (50–80% over TiN). Requires high cutting speeds to activate the aluminum oxide layer; at low speeds, TiAlN performs equally well.
When to use: High-speed finishing on steel and stainless. Hardened steel machining. Dry cutting at elevated speeds. Applications where TiAlN is wearing too fast.
AlCrN (Aluminum Chromium Nitride) — The Exotic Material Specialist
AlCrN is the extreme-temperature coating. With chromium replacing titanium, it maintains structural integrity up to 1,100°C — temperatures that destroy every other coating. The chromium content also provides exceptional oxidation resistance.
Strengths: Survives 1,100°C cutting temperatures. Mandatory for titanium alloys (Ti-6Al-4V), Inconel, Hastelloy, and other superalloys. The chromium content reduces chemical reaction between the coating and reactive workpiece materials. Tool life 2–3x longer than TiAlN on exotic materials.
Weaknesses: Most expensive standard coating (80–120% over TiN). Overkill for steel or standard stainless — you're paying for heat resistance you don't need. Fewer insert manufacturers offer it in all shapes.
When to use: Titanium alloys. Nickel-based superalloys (Inconel 718, Hastelloy). Super duplex stainless. Any material that generates cutting temperatures above 900°C. If you're machining aerospace materials, AlCrN is not optional.
Advanced coated carbide tools — engineered for extended tool life in the most demanding applications
Coating Selection by Material — Quick Decision Matrix
| Workpiece Material | Best Coating | Alternative | Avoid |
|---|---|---|---|
| Mild Steel (1018, 1045) | TiN or TiAlN | TiCN | AlCrN (overkill) |
| Medium Carbon (4140, 4340) | TiAlN | TiCN | TiN at high speed |
| Stainless Steel (304, 316) | TiAlN | AlTiN | TiN, uncoated |
| Duplex Stainless (2205) | TiAlN or AlCrN | AlTiN | TiN, TiCN |
| Cast Iron | TiAlN | TiCN | Uncoated |
| Aluminum Alloys | TiN or uncoated | TiCN | TiAlN, AlTiN (BUE risk) |
| Titanium (Ti-6Al-4V) | AlCrN | TiAlN (reduced speed) | TiN, TiCN, uncoated |
| Inconel / Hastelloy | AlCrN | None — AlCrN mandatory | Everything else |
| Hardened Steel (>45 HRC) | AlTiN | TiAlN | TiN, TiCN |
| Brass / Copper | TiN | Uncoated | AlCrN (unnecessary) |
Coating Economics: Cost vs. Tool Life
The cheapest insert is never the cheapest tool. Coating selection directly impacts cost-per-part — and premium coatings almost always win on economics.
| Coating | Typical Insert Cost | Tool Life (vs. TiN) | Cost-Per-Part Impact |
|---|---|---|---|
| TiN | AED 5–8 | Baseline (1x) | Baseline |
| TiCN | AED 7–10 | 1.3–1.5x | 10–20% lower |
| TiAlN | AED 8–12 | 2–4x | 30–50% lower |
| AlTiN | AED 10–15 | 3–5x | 40–60% lower |
| AlCrN | AED 12–18 | 2–3x (on exotic alloys) | 50–70% lower on titanium |
Brazed carbide turning tools — coating selection matters even for brazed tools
Frequently Asked Questions
Which coating lasts longest on stainless steel?
TiAlN lasts 2–4x longer than TiN on stainless steel. For standard austenitic grades (304, 316), TiAlN is the best balance of cost and performance. For duplex or super duplex stainless, consider AlCrN for even longer life.
Can I use TiAlN-coated inserts on aluminum?
Not recommended. The aluminum in TiAlN coating reacts with aluminum workpieces, promoting built-up edge and poor surface finish. Use TiN-coated or uncoated inserts for aluminum. Some manufacturers offer diamond-like carbon (DLC) coatings specifically for aluminum.
How can I tell what coating is on my insert?
Color is the primary indicator: gold = TiN, blue-gray = TiCN, dark violet/purple = TiAlN, black = AlTiN, silver-gray = AlCrN. However, multilayer coatings can vary. Check the manufacturer's documentation or the insert packaging for the specific coating designation.
Do coatings wear off? What happens underneath?
Yes, coatings are 2–6 microns thick and wear through during cutting. Once the coating wears through, the exposed carbide substrate wears rapidly — this is why coated inserts show sudden performance drops near end of life. The coating doesn't regenerate (except TiAlN/AlTiN which form aluminum oxide at high temp).
Is a more expensive coating always better?
Not always. AlCrN is the most expensive but performs worse than TiAlN on mild steel — you're paying for extreme heat resistance you don't need. Match the coating to the material: TiN for steel below 200 m/min, TiAlN for most work, AlCrN only for titanium and superalloys.
What coating should I use for dry machining?
TiAlN or AlTiN. Both coatings actually perform better at higher temperatures because the aluminum content forms a protective oxide layer. TiN and TiCN require coolant to stay within their temperature limits. If you're going dry, TiAlN is the minimum requirement.
Can I recoat a worn insert?
Technically possible but rarely worth it. Recoating requires stripping the old coating, re-grinding the edge, and reapplying — the cost often exceeds a new insert. The re-ground geometry is never as precise. New inserts are more cost-effective in almost all cases.
Why does my coated insert turn dark brown?
Dark brown discoloration means the coating has exceeded its temperature limit. On TiN inserts, this happens above 600°C. Solutions: switch to TiAlN coating, reduce surface speed by 20%, or improve coolant delivery. The discolored area has lost its protective properties.
Where can I get premium-coated inserts in Dubai?
San Tools in Al Quoz stocks carbide inserts in TiN, TiCN, TiAlN, and AlCrN coatings across all standard shapes. Visit the showroom to compare coatings side-by-side or browse the full range at santoolsme.com.
Key Takeaways
- TiAlN is the default. If you're buying one coating for everything except aluminum and exotics, this is it.
- TiN is fine for basic steel at low speed. Don't use it on stainless, high-speed work, or dry machining.
- AlCrN is mandatory for titanium and superalloys. Nothing else survives those temperatures.
- Premium coatings cost less per part. TiAlN at AED 10 outlasts TiN at AED 6 by 3x — do the math.
- Match coating to material, not to budget. The wrong coating fails fast regardless of the insert quality underneath.
- Avoid TiAlN on aluminum. Aluminum-on-aluminum causes built-up edge. Use TiN or uncoated instead.
Get the Right Coating for Your Material
San Tools carries carbide inserts in every major coating — TiN, TiCN, TiAlN, and AlCrN — across all standard shapes and sizes. Not sure which coating fits your application? Bring a sample part to our Al Quoz showroom and we'll recommend the optimal coating and grade.
Browse the full range at santoolsme.com or call +971 52 132 7742 for technical support.
Related: Carbide Insert Guide · Tool Geometry Guide · Stainless Steel Guide