Cutting tool coatings extend tool life 3-10× compared to uncoated equivalents by reducing friction at the cutting edge, increasing surface hardness, and improving thermal stability. The four most common coatings on industrial cutting tools are TiN (titanium nitride — gold-yellow, general purpose), TiAlN (titanium aluminium nitride — violet-grey, harder materials including stainless), AlCrN (aluminium chromium nitride — blue-grey, high-temperature and abrasive materials), and TiCN (titanium carbonitride — blue-grey, abrasive cast iron and tool steel). Each has a specific best-fit material and application profile, and choosing the wrong coating costs you 30-80% of potential tool life.
This reference compiles PVD coating data from manufacturer datasheets (Oerlikon Balzers, IHI Hauzer, Platit, Sulzer), ASM Handbook Volume 5 (Surface Engineering), and the cutting tool handbooks of Sandvik Coromant, Kennametal, Mitsubishi Materials, OSG and Iscar.
Cutting Tool Coatings — Properties at a Glance
Master reference table covering the major PVD (Physical Vapour Deposition) coatings used on industrial cutting tools, plus surface treatments (Steam Oxide, Plasma Nitride) commonly grouped with coatings. Properties are typical values — specific manufacturer formulations vary within a few percent.
| Coating | Composition | Microhardness (HV) | Friction vs Steel | Max Temp | Colour | Best For | Avoid In |
|---|---|---|---|---|---|---|---|
| TiN — Titanium Nitride | Ti + N | ~2,300 HV | 0.4 | ~600°C | Gold-yellow | General-purpose drilling and tapping, wide material range, 3-8× tool life vs uncoated, entry-level tier on most HSS tools | Hardened steels > 45 HRC, very high cutting speeds (above ~80 m/min on steel) |
| TiCN — Titanium Carbonitride | Ti + C + N | ~3,000 HV | 0.3-0.4 | ~400°C | Blue-grey to grey | Abrasive materials — grey cast iron, heat-treated steel, hardened tool steel up to ~50 HRC | High thermal applications (lower temp limit than TiN), aluminium (TiCN reacts with Al) |
| TiAlN — Titanium Aluminium Nitride (Futura) | Ti + Al + N (single layer or nano-layer) | ~3,300 HV | 0.30-0.35 | ~900°C | Violet-grey | Difficult-to-machine materials — stainless steel, alloy steel, titanium; higher cutting speeds; MQL or reduced coolant | Aluminium — Al chemically affinitates with Ti at cutting temperature, causing built-up edge and rapid wear |
| AlCrN — Aluminium Chromium Nitride (Alcrona) | Al + Cr + N | ~3,200 HV | 0.35 | ~1100°C | Blue-grey | Hardened steels up to 54 HRC; dry machining; MQL; aluminium (preferred over TiAlN — no Al-Cr chemical reaction) | Cryogenic / very low-temperature applications; cost-sensitive standard steel work where TiAlN is sufficient |
| Aldura — AlCrN + TiAlN Multi-Layer | Multi-layer Al-Cr-N + Ti-Al-N | ~3,300 HV | <0.4 | >1100°C | Blue-grey | Hardened steels > 60 HRC, very high thermal load, premium production work | Soft material (overkill, cost not justified vs single-layer TiAlN) |
| AlNova — Alcrona-based Multi-Layer | Multi-layer Al-Cr-N (Alcrona derivative) | ~3,200 HV | 0.35 | >1100°C | Light grey | Hardened steels with high abrasion + high cutting speed; excellent abrasion resistance | General-purpose carbon steel (overkill, AlCrN single-layer sufficient) |
| CrN — Chromium Nitride | Cr + N | ~1,750 HV | 0.5 | ~700°C | Silver-grey | Cutting and forming of copper, nickel, monel; corrosive environments; tools requiring excellent adhesion under high loads | Heavy-abrasion applications (lower hardness than Ti-based coatings) |
| Hardlube — TiAlN + WC/C Multi-Layer | Multi-layer Ti-Al-N with tungsten carbide / carbon top layer | ~3,000 HV | 0.15-0.20 | ~800°C | Dark grey | Tapping and drilling of hard-to-machine materials; MQL and dry machining; lowest friction coefficient of common coatings | Cost-sensitive applications (premium coating tier) |
| Helica — Alcrona-based Multi-Layer | Multi-layer Alcrona derivative optimised for high-feed drilling | ~3,000 HV | 0.25 | ~1100°C | Copper | High speeds + feeds in stainless and abrasive material; multi-regrindable; improved drill hole quality (used on Sutton Black Magic range) | Soft non-ferrous material (cost vs benefit doesn't pay back) |
| Steam Oxide — Blu | Iron oxide surface layer | Surface treatment (no microhardness boost) | 0.8-1.0 | (low — surface treatment, not a true coating) | Blue-black | Low-carbon steels — prevents chip BUE; oxide layer acts as lubricant carrier | High-stress, abrasive, or hardened materials |
| Plasma Nitride / Ni | Nitrided surface (case hardening, not a coating) | Surface treatment (~700-1100 HV depending on substrate) | 0.8-1.0 | (varies with substrate) | Dark grey to black | Cast iron and aluminium alloys (abrasive non-ferrous), where surface hardness boost helps | High-temp service (not a true coating, just surface treatment) |
| Diamond — PCD / CVD | Polycrystalline diamond (sp³ bonded carbon) | ~8,000-10,000 HV | 0.15 | ~600°C (decomposes higher) | Black or transparent | Non-ferrous metals only — aluminium at extreme speeds, copper alloys, graphite, composites (CFRP/GFRP), MMCs, ceramics | All ferrous metals — catalytic reaction between carbon and iron at cutting temperature dissolves the diamond (catastrophic failure) |
| Brt / Bright (uncoated) | Polished tool material surface | (varies with base material) | 0.8-1.0 | (varies with base material) | Silver | General-purpose mild steel, copper, brass, low-temperature non-ferrous; entry-level cost tier | High-load, high-temp applications, stainless steel at production volume |
Why Coatings Matter — The Three Mechanisms
1. Reduced Friction at the Cutting Edge
Uncoated HSS or carbide has a friction coefficient against steel of approximately 0.8-1.0. Modern PVD coatings reduce this to 0.15-0.40 — Hardlube (TiAlN + WC/C) achieves 0.15-0.20, the lowest in common use. Lower friction means less heat generated at the cut zone, lower power consumption, and slower edge wear.
2. Increased Surface Hardness
Coating microhardness is typically 2-4× the base tool material hardness. Solid carbide is ~1,400 HV; TiAlN coating on top is 3,300 HV. Hardness directly translates to abrasion resistance — the dominant tool wear mode for most cutting applications.
3. Thermal Stability
Uncoated HSS softens significantly above 500°C — the threshold where standard HSS loses 50% of its hardness. Modern coatings tolerate 600-1100°C edge temperatures with minimal hardness loss. This is the mechanism that lets carbide tooling run at 5× the cutting speed of HSS — the coating absorbs and tolerates the heat that would catastrophically soften an uncoated tool.
Matching Coating to Material
Quick selection table by workpiece material. Pair with the speeds & feeds in our cutting parameters reference for the full picture.
| Material | Best Coating | Reason |
|---|---|---|
| Mild steel (low-carbon) | TiN or Bright (uncoated) | Cost-effective; TiN extends life 3-5× |
| Medium-carbon steel (1045 etc.) | TiN or TiAlN | TiAlN justified at higher cutting speeds |
| Alloy steel (4140, 4340) | TiAlN | Higher temperature tolerance at production Vc |
| Stainless 304 / 316 | TiAlN (essential) | Austenitic stainless work-hardens — needs thermal stability + low friction |
| Hardened steels (>45 HRC) | AlCrN, Aldura, AlNova | Hot hardness retained at temperatures HSS cannot survive |
| Cast iron (grey, nodular) | TiCN (abrasion-resistant) or TiAlN | Abrasive Si and graphite — needs hard coating |
| Aluminium | AlCrN preferred — NOT TiAlN | Al-Ti chemical reaction with TiAlN causes built-up edge |
| Copper / brass / bronze | Bright (uncoated polished) or CrN | Ductile non-ferrous; coatings unnecessary at standard speeds |
| Titanium (Ti-6Al-4V) | TiAlN, AlCrN or Hardlube | Low thermal conductivity = heat at cutting edge — needs coating |
| Inconel / Hastelloy / nickel super alloys | AlCrN or Aldura | Hardest standard materials to machine — highest-spec coatings required |
| Composites (CFRP / GFRP), graphite, MMCs | Diamond (PCD / CVD) | Extreme abrasion — only diamond survives at speed |
TiN vs TiAlN — The Most Common Coating Question
The two most-encountered coatings on AIMS-stocked cutting tools. Visible difference: TiN is gold-yellow, TiAlN is violet-grey. The aluminium addition in TiAlN dramatically improves high-temperature performance:
- TiN max temperature ~600°C — adequate for cutting speeds up to ~60 m/min on steel
- TiAlN max temperature ~900°C — sustains cutting speeds 100-200 m/min comfortably
For most modern machining (any cutting speed above ~60 m/min), TiAlN outperforms TiN even on materials where TiN would technically be sufficient. TiN persists because it's cheaper and instantly recognisable (gold colour) on tap sets and entry-level HSS drills. For solid carbide tooling, TiAlN is the default standard.
AlCrN vs TiAlN — When to Pick Which
Both are modern multi-element coatings with similar hardness (~3,200-3,300 HV). The choice comes down to material and temperature:
- TiAlN — better in materials where cutting temperature stays below ~900°C. This covers the bulk of steel and stainless work at standard production speeds.
- AlCrN — better above 900°C (very high cutting speed, hard materials, dry machining, MQL). Also the correct choice for aluminium (no Al-Ti chemical reaction).
- For most stainless work at standard speeds, TiAlN is available, well-understood, and works fine. AlCrN is the premium choice when conditions get extreme.
Premium Multi-Layer Coatings — Worth the Premium?
Aldura, AlNova, Helica, Hardlube and similar multi-layer premium coatings cost 10-25% more than single-layer TiAlN. The payback depends on application:
- Production environments — tool consumption is significant; tool life improvement of 200-500% pays back the coating premium many times over. Justified.
- Workshop / one-off jobs — total tool cost is small relative to labour; standard TiAlN delivers 80%+ of the premium coating performance at lower cost. Premium coating not justified.
- Difficult materials (hardened steels, super alloys, Inconel) — premium coating sometimes the only viable option. Standard TiAlN may not survive.
Within Sutton's range, the Helica coating appears on the Black Magic D356 / D358 carbide drills. AlCrN appears on the D323 / D326 / D329 / D332 / D335 series. TiCN appears on entry-tier D306 / D310 carbide drills (the most common in AIMS stock).
AIMS Coated Cutting Tool Range
AIMS Industrial stocks the major coating tiers across HSS, cobalt and solid carbide tooling:
- TiN-coated HSS — entry-tier drills and taps. Cost-effective for general-purpose work.
- TiCN-coated solid carbide drills — Sutton D306 (Imperial and Metric) and Sutton D310 (Imperial and Metric) series. The most common AIMS-stocked carbide drill tier.
- AlCrN-coated solid carbide drills — Sutton D323, D326, D329, D332, D335 series. Premium performance on harder materials.
- Helica (Alcrona-based) — Sutton Black Magic D356 (3xD) and D358 (5xD) — premium production tier.
Browse the full carbide drill bit collection for coated options, or cobalt drill bits for the HSS-Co tier. Sutton's full range is at Sutton Tools at AIMS.
Need a specific coating for a tricky material — particularly aluminium (where AlCrN is required, not TiAlN), or hardened steel (where Aldura or AlNova justifies the premium)? Contact AIMS on (02) 9773 0122 — we'll match the coating to the application.
Frequently Asked Questions
Q: What's the difference between TiN and TiAlN coatings?
TiN (Titanium Nitride) is the classic gold-yellow coating, max temperature ~600°C, hardness ~2,300 HV — adequate for cutting speeds up to ~60 m/min on steel. TiAlN (Titanium Aluminium Nitride) is violet-grey, max temperature ~900°C, hardness ~3,300 HV — supports cutting speeds 100-200 m/min on steel and is the modern standard for solid carbide tooling. The aluminium addition in TiAlN dramatically improves high-temperature performance.
Q: Should I use a TiN or TiAlN coated drill for stainless steel?
TiAlN. Austenitic stainless (304, 316) work-hardens rapidly under cutting pressure — the cutting zone gets very hot, and TiN coating loses hardness above ~600°C. TiAlN's higher thermal stability (~900°C max) handles the heat. For cobalt HSS drills, TiAlN is the standard premium upgrade. For carbide drills in stainless, TiAlN is the default.
Q: Why is TiAlN bad for aluminium?
Chemical affinity. At cutting temperatures, the titanium in TiAlN chemically reacts with the aluminium in the workpiece — Al and Ti form intermetallic compounds, causing built-up edge (BUE) on the cutting tool. The BUE distorts the cutting geometry, causes poor surface finish, and accelerates tool wear. For aluminium, use AlCrN coating (no Ti-Al reaction) or uncoated polished carbide.
Q: What does AlCrN mean on a drill bit?
Aluminium Chromium Nitride — a modern multi-element PVD coating with hardness ~3,200 HV and excellent thermal stability up to ~1100°C. AlCrN is the preferred coating for hardened steels (up to 54 HRC), aluminium (replaces problematic TiAlN), and dry/MQL machining applications. On Sutton drills, AlCrN appears on the D323, D326, D329, D332 and D335 series.
Q: What coating for cutting hardened steel?
For materials up to 45 HRC, TiAlN remains workable. Above 45 HRC, AlCrN is the standard choice. Above 55 HRC, multi-layer premium coatings (Aldura, AlNova) extend tool life significantly. Above 60 HRC, you're approaching the limits of even premium coated carbide — for production work, PCBN inserts often become more economical.
Q: Can I use a coated drill bit on cast iron?
Yes — cast iron is highly abrasive (silicon carbide and graphite content), so coatings extend tool life substantially. TiCN (titanium carbonitride) is the traditional choice for cast iron — its high hardness resists the abrasive wear mode. TiAlN also works well. Note: cast iron is typically machined dry, as the graphite acts as a natural lubricant and water-based coolant can cause workpiece corrosion.
Q: What's the gold colour on drill bits?
TiN (Titanium Nitride) coating. The gold-yellow colour is characteristic of TiN and instantly recognisable. It's the original commercial PVD coating, applied to industrial cutting tools since the early 1980s. While newer coatings (TiAlN, AlCrN) outperform it at higher speeds, TiN remains common on entry-tier HSS drill bits and taps because it's inexpensive and effective at standard cutting speeds.
Q: How long do cutting tool coatings last?
The coating itself is typically 2-5 microns thick and wears down progressively over the tool's life. Coating life depends on cutting parameters, material, and coolant — typical life is 5-20× longer than the same tool uncoated. When the coating wears through to bare tool material, the wear rate accelerates rapidly. For regrindable tools (solid carbide endmills, larger drills), tools can be re-coated 1-3 times during their service life by specialist re-coaters.
Q: Are diamond-coated drills better than carbide?
Only for specific materials. Diamond (PCD or CVD diamond) is the hardest cutting tool material — about 3× the hardness of TiAlN. But diamond chemically reacts with iron at cutting temperatures, dissolving rapidly. So diamond is for non-ferrous materials only: aluminium at extreme speeds, copper alloys, graphite, composites (CFRP, GFRP), MMCs, ceramics. For any ferrous metal (steel, stainless, cast iron), carbide with TiAlN or AlCrN coating outperforms diamond.
Q: What's the difference between AlCrN and Aldura?
AlCrN (Alcrona) is a single-element-layer coating. Aldura is a multi-layer combination of AlCrN with TiAlN — alternating thin layers (~50nm each) of the two compounds. The multi-layer structure improves toughness against thermal shock and abrasion while maintaining the high temperature stability of AlCrN. Aldura is positioned as a premium coating for hardened steel applications above 60 HRC where neither AlCrN nor TiAlN alone is sufficient.
Q: Why is my TiAlN drill getting BUE in aluminium?
Chemical affinity between titanium (in TiAlN coating) and aluminium (workpiece). The fix is to switch to AlCrN coating — no Al-Cr chemical reaction means no built-up edge. Alternatively, use uncoated polished solid carbide. For one-off jobs, increasing cutting speed (more heat, less BUE) and using flood coolant can mitigate but not eliminate the problem on TiAlN tools.
Q: What's PCD coating?
PCD stands for Polycrystalline Diamond. Strictly speaking, PCD is an insert material (a diamond tip brazed onto a carbide substrate) rather than a coating — though the term is often used loosely. CVD (Chemical Vapour Deposition) diamond is a true diamond coating applied to carbide. Both are extreme-hardness tooling reserved for non-ferrous machining (aluminium, copper, composites, graphite) where their performance justifies the high cost. Never use diamond on ferrous metals.
Related AIMS Engineering Reference Guides
- Workpiece Material Cross-Reference Chart — identify your material group first
- Cutting Speeds & Feeds Master Reference — pair coating with correct Vc and feed
- Cutting Tool Troubleshooting Master — when the wrong coating causes problems
- Cobalt Drill Bit Guide — HSS-Co base material context
- Carbide vs HSS End Mills — base tool material context