Cutting Tool Coatings Explained: TiN, TiAlN, AlCrN and DLC
Coatings do not make a bad tool good. They extend the life of a correctly designed tool in the right material. Here is what each coating actually does and when to use it.
A coating is a surface treatment chosen to reduce friction, raise temperature resistance or stop the coating material reacting with the chip. Choosing one means choosing it against the workpiece, not against a preference.
TiN — Titanium Nitride
The gold-coloured coating, the workhorse of general machining. Raises hardness and reduces friction against steel and cast iron. The right default where nothing unusual is in the workpiece, and the coating most often applied by default in general supply.
TiAlN — Titanium Aluminium Nitride
The purple coating. Higher temperature resistance than TiN, which is why it dominates in hardened steel, stainless and austenitic materials. The standard choice for carbide micro drills and mills running in hardened workpiece material.
AlCrN — Aluminium Chromium Nitride
Higher oxidation resistance still, and the coating of choice in titanium, superalloys and aerospace materials where the chip temperature is high and titanium aluminides would otherwise form. The coating we specify most often for aerospace micro tooling.
ZrCN — Zirconium Chromium Nitride
Good combination of hardness and lubricity, useful in aluminium and non-ferrous materials and in operations with interrupted cuts. A strong option where built-up edge is the main failure mode.
DLC — Diamond-Like Carbon
Extremely low friction coefficient, chemically inert and wear resistant. The right surface for aluminium, copper, CFRP, graphite and adhesive layers. It is not suitable for iron-family materials, where the coating can react at cutting temperatures — specifying DLC for steel is one of the commonest specification errors we see.
The rule of thumb
- Hardened steel, stainless — TiAlN or AlCrN
- Titanium, superalloy — AlCrN
- Aluminium, copper, CFRP — DLC or ZrCN
- General mixed work — TiN
- Sensitive materials, risk of reaction — uncoated
What matters more
A well-designed geometry with the wrong coating will underperform a less elegant geometry with the right one. If we are designing a tool for you, the coating is the last variable we set, not the first.
Does this apply to your part?
Send the drawing and we will tell you, not guess.
Related notes.
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September 28, 2026Micro End Mill Selection Guide for Miniature Features
Flat, ball nose, V-bit or chamfer? Micro end mill selection comes down to the feature geometry, the chip load
September 16, 2026Micro Reamers: Achieving Tight Hole Size Control
Reamers exist because drills cannot hold the tolerance. This guide covers spiral versus straight reamers, tape
September 4, 2026What we make.
Micro drills from 0.03 mm, in standard, helical, step, left-hand and aluminium-grade geometry. Every entry is a live, shipped configuration.
End mills from 0.1 mm across single and double flute, helical and straight, ball and flat geometry, with aluminium- and acrylic-dedicated lines.
Single and double flute chamfer mills, ball-tip finishing cutters, flat-bottom finishing cutters and extended-reach versions for deep features.
