Understanding how surface treatment can extend the life of cold heading punches, dies, and other tooling components
In One Sentence
Surface treatment is one of the most effective ways to extend the life of cold forming tooling — PVD coatings, nitriding, and DLC coatings each address different failure mechanisms, and the right choice depends on the dominant wear mode, workpiece material, and operating conditions. However, surface treatment is not a substitute for correct material selection and heat treatment; it works best when applied to a properly heat-treated substrate with the right surface preparation.
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1. Why Surface Treatment Matters
Many important cold-forming tool failure mechanisms originate at or are strongly influenced by the tool-workpiece interface — particularly wear and galling. Surface treatment modifies that interface to:
Increase surface hardness — improving resistance to abrasive wear and plastic deformation
Reduce friction — lowering forming forces and reducing adhesive wear
Improve hot hardness and oxidation resistance — helping protect the tool surface under elevated-temperature conditions
Improve corrosion resistance — protecting against aggressive environments
Extend tool life — by addressing the specific failure mechanism that limits performance
Reducing friction at the tool-workpiece interface can reduce forming loads and local tool stresses in suitable applications, but the magnitude depends strongly on the forming process and operating conditions.
2. The Role of the Substrate
Surface treatment does not work in isolation. The substrate — the base tool steel — determines how well the coating performs.
Key substrate considerations:
Hardness — a properly hardened substrate provides mechanical support for the coating
Surface finish — excessive surface roughness causes premature coating spallation. Precision grinding and polishing before coating are essential
Cleanliness — contamination weakens coating adhesion
Heat treatment condition — the substrate must be correctly heat-treated before coating
Important: A coating cannot compensate for a poorly heat-treated or poorly machined substrate. The best results come from a properly selected and heat-treated tool steel, precision-ground to the correct finish, and then coated.
For a detailed guide on heat treatment for cold forming tooling, see our Heat Treatment for Cold Forming Tooling: Quenching, Tempering & Cryogenic Treatment.
3. PVD Coatings
Physical Vapour Deposition (PVD) is a widely used surface treatment for cold forming tooling. In the PVD process, a thin, hard layer is deposited on the tool surface in a vacuum chamber — the coating material is vaporised and ionised into a plasma state, then deposited onto the tool surface to form a high-adhesion coating.
Key characteristics:
Thickness: typically 2–5 μm, depending on coating composition and supplier process
Deposition temperature: varies by coating process and must remain compatible with the substrate’s previous heat-treatment condition. The coating temperature should generally be controlled below the temperature at which unacceptable tempering or dimensional changes would occur
Hardness: significantly harder than the substrate steel — typical reported ranges are 2000–3200 HV, depending on coating type
Benefits: increased surface hardness, reduced friction, improved hot hardness, corrosion protection
| Coating | Typical Characteristics | Evaluation Considerations |
|---|---|---|
| TiN (Titanium Nitride) | High hardness, general-purpose, gold colour | May be considered for general forming; good wear resistance but limited high-temperature performance |
| TiCN (Titanium Carbonitride) | Higher hardness than TiN, improved wear resistance | May be evaluated for forming on carbon steel; good for applications requiring high surface hardness |
| CrN (Chromium Nitride) | Good adhesion, high toughness, good corrosion resistance | May be considered for forming non-ferrous metals such as aluminium and copper; effective at reducing adhesive wear |
| AlTiN (Aluminium Titanium Nitride) | Extreme wear resistance at high temperature, excellent oxidation resistance | May be evaluated for forming high-strength materials, piercing, and extrusion where heat is a factor |
| AlCrN (Aluminium Chromium Nitride) | High oxidation resistance, excellent hot hardness | May be considered for forming stainless steel and high-temperature applications |
Note: Coating selection depends on the workpiece material, lubricant, working temperature, machine speed, and substrate condition — not on a single universal recommendation. Reported performance varies significantly by application.
4. Nitriding
Nitriding is a diffusion-based surface hardening process that introduces nitrogen into the tool steel surface, forming a hard nitride layer.
Key characteristics:
Process: typically plasma nitriding or gas nitriding
Hardened layer depth: typically 0.05–0.3 mm, depending on process and steel grade
Hardness: surface hardness can reach 900–1200 HV, depending on the steel grade
Benefits: increased surface hardness, improved wear resistance, good fatigue resistance
Application considerations:
May be applied to suitable tool steels where alloy composition, prior heat treatment, and required case properties support nitriding
Provides a deeper hardened layer than PVD coatings
Can be combined with PVD coating for a duplex treatment — nitriding first, then PVD coating on top
The nitrided surface may require mechanical preparation before PVD coating to ensure coating adhesion
Important: Nitriding temperature and time must be selected for the specific steel and prior heat-treatment condition, normally using a validated process that avoids unacceptable softening or dimensional change of the substrate.
Duplex treatment (nitriding + PVD):
A properly designed duplex system can improve load support for the PVD coating. Coating adhesion still depends on nitrided-layer condition, surface preparation, and the subsequent coating process.
5. DLC Coatings
Diamond-Like Carbon (DLC) is a family of amorphous carbon-based coatings. Hardness, friction, temperature capability, and thickness vary substantially with coating type and deposition process.
Representative ranges:
Hardness: typically 1500–2500 HV, depending on coating type
Friction coefficient: typically 0.03–0.1, compared to 0.3–0.5 for uncoated tool steel
Thickness: typically 1–3 μm
Deposition temperature: low — typically below 200°C
Benefits: excellent anti-galling and anti-adhesion properties, low friction, good wear resistance
Application considerations:
Particularly effective for reducing adhesive wear and galling
Suitable for forming non-ferrous metals and for applications where workpiece surface quality is critical
Low deposition temperature makes it suitable for tools that have already been heat-treated
Some DLC deposition processes can coat selected complex or internal features, subject to geometry, accessibility, and the coating supplier’s process capability
6. Comparing Surface Treatment Options
| Treatment | Hardness | Depth / Thickness | Key Benefit | Typical Application |
|---|---|---|---|---|
| PVD (TiN, TiCN, CrN, AlTiN, AlCrN) | 2000–3200 HV | 2–5 μm | Wear resistance, reduced friction, hot hardness | General forming, high-wear applications |
| Nitriding | 900–1200 HV | 0.05–0.3 mm | Deep hardened layer, fatigue resistance | Substrate hardening, duplex treatment |
| DLC | 1500–2500 HV | 1–3 μm | Very low friction, anti-galling | Adhesive wear, non-ferrous forming, surface-critical parts |
| Treatment | Hardness | Depth / Thickness | Key Benefit | Typical Application |
|---|---|---|---|---|
| PVD (TiN, TiCN, CrN, AlTiN, AlCrN) | 2000–3200 HV | 2–5 μm | Wear resistance, reduced friction, hot hardness | General forming, high-wear applications |
| Nitriding | 900–1200 HV | 0.05–0.3 mm | Deep hardened layer, fatigue resistance | Substrate hardening, duplex treatment |
| DLC | 1500–2500 HV | 1–3 μm | Very low friction, anti-galling | Adhesive wear, non-ferrous forming, surface-critical parts |
7. Selecting the Right Surface Treatment
The right surface treatment depends on why the tool is failing.
| Failure Mode | Verification Focus | Surface Treatment Considerations* |
|---|---|---|
| Abrasive Wear | Identify abrasive source; check substrate hardness | PVD coatings (TiN, TiCN, AlTiN) may improve wear resistance |
| Adhesive Wear / Galling | Review lubrication, surface finish, material compatibility | DLC or CrN may reduce adhesion and friction |
| Thermal Wear | Review cutting speed, cooling, temperature | AlTiN or AlCrN may offer improved hot hardness and oxidation resistance, helping protect the tool surface under elevated-temperature conditions |
| Fatigue Cracking | Review geometry, surface finish, residual stress | Nitriding may improve fatigue resistance where the nitrided layer and residual-stress condition are appropriately controlled; surface finish is critical |
| Plastic Deformation | Verify substrate hardness, load, temperature | Nitriding may increase surface hardness; consider substrate heat treatment first |
Surface treatments are candidate options for evaluation, not definitive recommendations. Final selection must be validated against the specific application conditions and production history.
8. Practical Sourcing & Specification Tips
1. Specify the substrate condition first.
Surface treatment works best on a properly heat-treated and precision-ground substrate. Specify hardness range, surface finish, and heat treatment condition before specifying the coating.
2. Match the treatment to the failure mode.
Do not apply a coating simply because it is available. Identify the dominant failure mode and select a treatment that addresses it. A coating that works well for abrasive wear may not be the best choice for adhesive wear or fatigue.
3. Consider duplex treatment where appropriate.
Combining nitriding with PVD coating can provide a hard, load-bearing substrate with a wear-resistant surface layer in applications where the substrate/coating system benefits from a hardened diffusion layer.
4. Validate with your tooling supplier.
Surface treatment performance depends on many factors — substrate material, heat treatment, surface preparation, coating process, and operating conditions. Work with a supplier experienced in cold forming tooling to select and validate the right combination.
5. Track results and adjust.
Record the coating type, treatment parameters, and tool life for each application. This data is the most reliable basis for improving surface treatment selection.
Need help selecting the right surface treatment for your cold forming tooling?
We machine cold forming tooling from a range of tool steels — including 1.2379, 1.3343, 1.2344, and 1.2601 — and work with qualified surface treatment partners to deliver the right combination of substrate properties and surface protection for your application.
For selected precision features and suitable geometries, our production records include tolerances down to ±0.005 mm.
Contact us and send us your drawing or specification, and we’ll help define the right surface treatment for your tooling.
Continue reading:
Transfer Fingers for Cold Forming & Stamping: Material, Precision & Surface Treatment Guide
Cold Heading Punches & Punch Pins: Material Selection & Precision Machining Guide
Cut-off Knives for Cold Heading: Material Selection & Performance Guide
Cold Heading Dies & Inserts: Material Selection & Precision Machining Guide
Tool Steel Selection for Cold Forming Tooling: A Practical Guide
Cold Heading Punches: 5 Common Failure Modes and How to Prevent Them
Cold Heading Dies & Inserts: Common Failure Modes and How to Prevent Them
Cut-off Knives for Cold Heading: Common Failure Modes and How to Prevent Them
1.2379 vs 1.3343 for Cold Heading Punches: Which Tool Steel Should You Choose?
Heat Treatment for Cold Forming Tooling: Quenching, Tempering & Cryogenic Treatment
References
EN ISO 4957:2018 — Tool steels (reference for tool steel grade properties)
ASTM A600 — Standard Specification for High-Speed Tool Steels (reference for M2 grades)
ASTM E18 — Standard Test Method for Rockwell Hardness of Metallic Materials
Industry practice references for surface treatment of cold forming tool steels
Editorial Note
This document is educational content only. All surface treatment descriptions, material recommendations, and capability statements are for general reference and require technical validation against actual application conditions before formal production release.