· KAIPU Engineering · coatings-comparison · 7 min read
PVD Coating Comparison Table for Industrial Blades
TiN, TiCN, CrN, AlCrN, TiAlN, DLC and CrAlN compared across hardness, friction coefficient, max operating temperature, substrate fit and field performance. A side-by-side reference for industrial slitter, shear and granulator blades.
A PVD (physical vapour deposition) coating is a 1–5 µm ceramic layer on the cutting edge of an industrial blade. The coating reduces friction, increases surface hardness, and — for the right coating on the right substrate — extends knife life by 20–50 %. The wrong coating on the wrong substrate is wasted money, and on impact-loaded applications a coating can accelerate chipping by adding a brittle ceramic layer to a steel that is already on the edge of its toughness window.
This page is the side-by-side reference we use at KAIPU when an RFQ asks “should we coat this knife, and with what?” It is a living document — the field data refreshes every 6 months. The table is structured for direct quotation in an RFQ response or a knife specification.
One-line summary: For paper and film slitting, TiN or CrN. For stainless and high-temperature cutting, AlCrN or TiAlN. For sticky polymers and austenitic stainless, DLC. For granulator and impact-loaded parts, no coating or a thin CrN.
PVD coating comparison table
| Coating | Hardness (HV) | Friction (dry, vs steel) | Max operating temp (°C) | Colour | Thickness (µm) | Best for | Avoid on | Relative cost |
|---|---|---|---|---|---|---|---|---|
| TiN (Titanium Nitride) | 2,300 | 0.40–0.50 | 600 | Gold | 2–4 | General-purpose slitting, paper, film, packaging | Sticky polymers, austenitic stainless | 1.0× (baseline) |
| TiCN (Titanium Carbonitride) | 2,800 | 0.30–0.40 | 450 | Blue-grey | 2–4 | Abrasive substrates, recycled polymers, non-woven | High-temperature cutting (above 400 °C) | 1.1× |
| CrN (Chromium Nitride) | 2,000 | 0.35–0.45 | 700 | Silver-grey | 3–5 | Corrosion-resistant, copper-cutting, food-grade lines | High-speed abrasive (TiN is better) | 1.1× |
| AlCrN (Aluminium Chromium Nitride) | 3,200 | 0.35–0.45 | 900 | Blue-grey / dark | 2–4 | High-temperature cutting, hard machining, dry cutting | Thin knives (risk of micro-cracking) | 1.4× |
| TiAlN (Titanium Aluminium Nitride) | 3,300 | 0.40–0.50 | 850 | Violet-black | 2–4 | Hot-work tooling, high-speed dry cutting, foil slitting | Impact-loaded parts | 1.4× |
| CrAlN (Chromium Aluminium Nitride) | 3,000 | 0.35–0.45 | 900 | Dark grey | 2–4 | Tough general-purpose high-temp, granulator bed knives | Cost-sensitive applications | 1.4× |
| DLC (Diamond-Like Carbon) | 2,000–5,000 | 0.05–0.15 | 350 | Black | 1–3 | Sticky polymers, austenitic stainless, aluminium, copper | High-temperature cutting | 2.0–3.0× |
| a-C:H (hydrogenated DLC) | 1,500–3,000 | 0.05–0.20 | 350 | Black | 1–2 | Polymer film slitting, food-contact, low-temp only | Hard substrates, high temp | 2.0× |
| ta-C (tetrahedral amorphous carbon) | 3,000–6,000 | 0.05–0.10 | 400 | Black | 0.5–2 | Aluminium foil, sticky polymer film, medical blades | Impact, thick deposits | 3.0× |
| Al₂O₃ (Alumina, CVD only) | 2,100 | 0.50–0.60 | 1,100 | White | 5–10 | High-temperature metal cutting inserts | Thin industrial knives (CVD requires > 500 °C) | 2.5× |
Notes on the table:
- Hardness values are typical for the PVD coating as deposited. They are not the same as the underlying tool-steel hardness and they do not measure coating toughness.
- Friction coefficients are “dry vs steel” reference values from coating-vendor datasheets. In service, with a lubricant, the effective friction is much lower and the differences between coatings narrow.
- Max operating temperature is the temperature at which the coating starts to oxidise or lose hardness, not the temperature at which it fails. Substrate failure typically precedes coating failure.
- Relative cost is the cost of the PVD coating step on a 250 mm OD slitter, indexed to TiN as the baseline. It does not include the underlying knife cost.
Coating-by-substrate recommendation
| Substrate / application | First choice | Second choice | Notes |
|---|---|---|---|
| Paper slitter (60–200 gsm) | TiN | CrN | TiN is the safe default. CrN for food-grade lines. |
| Tissue slitter (high speed, > 1,000 m/min) | TiCN | CrAlN | TiCN for abrasive tissue. CrAlN for very high temp. |
| Film slitter (PE, PP, PET) | TiN | CrN | CrN for food-contact film. |
| BOPP / BOPET thin film (12–25 µm) | DLC or a-C:H | CrN | DLC eliminates film sticking. |
| Sticky polymer / PVC / rubber | DLC | CrN | DLC’s low friction is decisive. |
| Aluminium foil slitter | ta-C or DLC | TiAlN | ta-C eliminates aluminium weld. |
| Austenitic stainless (304 / 316) | DLC | CrN | DLC eliminates galling. |
| Corrugated slitter | TiCN | TiN | Abrasive liners, high wear. |
| Abrasive non-woven | TiCN | TiN | High wear + some thermal. |
| Recycled polymer granulator bed | TiCN | CrAlN | Impact + abrasive. Avoid DLC (low temp limit). |
| Paper shear blade | TiN | — | General purpose. |
| Stainless plate shear | AlCrN | TiAlN | High temp + wear. |
| Carbon steel plate shear ≤ 6 mm | TiN | AlCrN | General purpose. |
| Food-contact cutting | CrN | a-C:H | CrN is food-contact safe; DLC inert. |
| Medical / surgical | DLC or ta-C | CrN | Inert, low friction. |
| Granulator rotor knife | None | CrN (thin) | Impact: coating can chip. |
| Crusher blade | None | None | High impact: no coating. |
How the coating is applied
All the coatings in the table are PVD (Physical Vapour Deposition), applied at temperatures between 200–500 °C in a vacuum chamber. The process:
- Pre-treatment. Knife is cleaned, degreased, and plasma-etched to ensure adhesion.
- Heating. Knife is heated to deposition temperature (typically 400–500 °C for nitride coatings, 150–200 °C for DLC).
- Deposition. Metal vapour (Ti, Cr, Al) is generated by arc or sputtering and reacts with nitrogen, carbon or oxygen to form the coating on the knife surface.
- Cool-down. Slow cool to avoid thermal shock, especially on thin knives and HSS substrates.
The deposition temperature matters. A 500 °C deposition on a HRC 64 HSS knife will temper back the steel and lose 2–4 HRC points. Specify a low-temperature PVD process (200–350 °C) for HSS and D2 / SKD11 knives above HRC 60. For tool steels below HRC 60, the standard 450 °C PVD is fine.
DLC and ta-C are deposited at 150–200 °C specifically to avoid this temper-back. They are the only coatings that should be specified for HSS knives above HRC 62.
Coating thickness and edge geometry
A 3 µm coating on a 5 µm hone adds 3 µm to each side of the edge, reducing the effective hone to negative — the knife becomes sharp at the coating surface but the underlying steel edge geometry is now a “reverse” hone. This is the single most common cause of coating-related field failures.
Rule of thumb: the underlying steel hone must be at least 2× the coating thickness. A 3 µm TiN coating needs a 6 µm steel hone minimum. A 1 µm DLC coating needs a 2 µm steel hone minimum.
If the customer wants a “sharp” edge, do not apply a thick coating. Use ta-C (0.5–1 µm) and a 1–2 µm steel hone.
When not to coat
A coating is not always the right answer. Skip the coating on:
- Granulator rotor knives. The impact loads chip the brittle ceramic layer faster than it wears. The cost of the coating exceeds the life gain.
- Crusher blades. Same reason — impact, not wear, is the failure mode.
- Knives below HRC 55. The substrate wears faster than the coating, and the coating flakes off.
- Knives that will be re-sharpened. Each re-grind removes 5–20 µm of substrate, which removes the coating on the back face. A re-sharpened knife is essentially uncoated on the re-ground surfaces. Re-coat after re-grind for critical applications.
- Knives with an aggressive hone (< 5 µm steel hone). A 3 µm coating will leave a negative hone; see above.
Coating inspection and quality control
A coated knife should arrive with:
- Coating thickness report. 5-point measurement on a calibration coupon, target ± 0.5 µm.
- Adhesion test. Rockwell indentation or scratch test, no delamination at the test load.
- Visual inspection. Uniform colour, no pinholes, no flaking, no uncoated areas on functional surfaces.
- Coating composition. EDS or XRD report on a sample, target stoichiometry within ± 5 %.
If your supplier cannot show you these four items, change supplier. A bad coating is worse than no coating.
Field cases
Case 1: Paper slitter, 250 mm, 600 m/min. Customer running D2 uncoated, 14-day life. We applied TiN. Life: 21 days. ROI: 4 months. Standard recommendation for paper slitting.
Case 2: 304 stainless slitter, 0.4 mm, 250 m/min. Customer running D2 uncoated, galling after 2 hours. We applied DLC. No galling, life 12 days. ROI: 3 months. DLC is the right answer for austenitic.
Case 3: Aluminium foil slitter, 50 µm, 300 m/min. Customer running D2 uncoated, 5 days. We tried TiN — 8 days. We tried ta-C — 18 days. The ta-C’s ultra-low friction eliminated the aluminium weld.
Case 4: Tissue slitter, 320 mm, 1,200 m/min. Customer running M4 uncoated, 19 days. We applied TiAlN. Life: 31 days. The TiAlN held the edge temperature below the M4’s softening point.
How to specify a coating on an RFQ
For a coated industrial blade, the spec should read:
“PVD coating: [TiN / TiCN / CrN / AlCrN / TiAlN / DLC / ta-C], thickness [2–4] µm, deposition temperature ≤ [350 °C for HSS, 450 °C for D2 / SKD11], coating supplier [name], coating report with thickness, adhesion test, composition. Underlying steel hone [≥ 2× coating thickness]. Do not coat functional surfaces marked ‘uncoated’.”
This phrasing locks the critical variables and lets the coating house recommend the deposition process.
For the broader five-factor selection method, see The KAIPU 5-Factor Blade Selection Framework. For the steel-grade cross-reference behind the choice, see Material Grade Converter. For a runnable comparison of carbide grades, see YG6X vs YG8.
For a written coating recommendation on your specific RFQ, send the part drawing, the substrate, the line speed and the current service life to engineering@kaipu-industrial.com or use the request-a-quote form. Specification, FOB quote and lead time within one business day.
About the author
KAIPU Engineering is the technical team at KAIPU Industrial Blades, in operation since 1998. ISO 9001:2015 certified. In-house PVD coating line for TiN, TiCN, CrN, AlCrN, TiAlN, DLC and ta-C.