Die Coating Technologies: TiN, TiCN and DLC Coatings for Stamping Dies

Die coating is the fastest payback upgrade available to most stamping operations. A $400 PVD coating job on a D2 blanking punch can extend tool life from 200,000 strokes to over 1,000,000 strokes — a 5× gain with no press changes, no new tooling steel, and no process redesign. Yet most press shops still make coating decisions based on sales brochures rather than tribological data. This article gives you the technical framework to choose correctly.

The four coatings that dominate stamping are TiN (titanium nitride), TiCN (titanium carbonitride), TiAlN (titanium aluminum nitride), CrN (chromium nitride), and DLC (diamond-like carbon). Each has a distinct hardness range, friction coefficient, maximum operating temperature, and adhesion behavior against different sheet materials. Getting the selection wrong costs more than not coating at all — a DLC coating on a poorly supported D2 insert will spall and contaminate the part surface within 50,000 strokes.

The background section below establishes what coatings do physically. The technical deep-dive quantifies the key parameters. The selection framework converts those parameters into production decisions.

What Die Coatings Do — Physical Mechanism and Deposition Methods

A die coating does three things simultaneously: it raises surface hardness above the base substrate, it reduces the coefficient of friction between tool and sheet metal, and it acts as a diffusion barrier that prevents adhesive wear (galling). None of these effects work independently.

Adhesive wear is the dominant failure mode in stamping dies. When two metallic surfaces slide under load, asperities weld and tear. The torn material transfers from the softer surface (usually the sheet) to the harder surface (the die). This is galling. Once a gall nodule forms on a punch face, every subsequent stroke produces scratches on the part. The nodule grows exponentially. A TiCN coating at 3000 HV is 10× harder than the galvanized sheet it contacts and chemically inert to zinc — galling is eliminated.

Abrasive wear dominates in high-silicon steels (AHSS, UHSS) and hard abrasive particles trapped in the lubricant. Abrasive wear rate follows Archard’s law: W = K × F × L / H, where W is wear volume, F is normal force, L is sliding distance, and H is hardness. Higher coating hardness directly reduces wear volume.

Deposition methods determine coating structure and adhesion:

• PVD (Physical Vapor Deposition): Base substrate is cleaned, placed in a vacuum chamber (10⁻⁵ to 10⁻⁶ mbar), and bombarded with ions from a metallic target. Process temperature stays below 500°C, so heat-treated tool steel retains its hardness. Film thickness: 2–5 µm. All TiN, TiCN, TiAlN, and CrN coatings used in stamping are PVD.
• CVD (Chemical Vapor Deposition): Reactive gases deposit coating at 900–1050°C. Excellent adhesion and thicker films (8–20 µm), but process temperature exceeds the tempering temperature of most tool steels — the substrate loses hardness. Used primarily on carbide inserts.
• PACVD (Plasma-Assisted CVD) / DLC: DLC is deposited at 150–250°C by PACVD or filtered cathodic arc. The low temperature makes it compatible with fully hardened tool steel and even carburized case-hardened dies.

The rest of this article focuses on PVD and PACVD coatings, which are the relevant options for stamping tooling.

Technical Deep-Dive: Hardness, Friction, Temperature and Thickness Data

The table below summarizes the core parameters for the five main die coatings. Values are measured by nanoindentation (hardness), pin-on-disk tribometer (friction), and thermal oxidation tests.

Coating Performance Comparison

Coating	Hardness (HV)	Friction Coeff. (dry, vs. steel)	Max. Service Temp. (°C)	Typical PVD Thickness (µm)	Color
TiN	2300–2500	0.40–0.55	600	2–4	Gold
TiCN	2800–3500	0.20–0.35	450	2–4	Blue-grey
TiAlN	3000–3500	0.35–0.55	800	2–5	Dark grey/violet
CrN	1800–2200	0.30–0.45	700	2–6	Silver
DLC (a-C:H)	1500–3500	0.05–0.15	300–350	1–3	Black
DLC (ta-C)	4000–7000	0.05–0.10	400	0.5–2	Black
Uncoated D2	800–850	0.60–0.80	—	—	—
Uncoated PM-HSS	850–950	0.60–0.80	—	—	—

Key observations:

• DLC ta-C is the hardest coating available, approaching that of CVD diamond. But its adhesion requires an intermediate bonding layer (typically CrN or TiN), and it is extremely sensitive to surface preparation — any residual stress crack or micro-porosity in the substrate will cause cohesive failure.
• TiAlN outperforms TiN and TiCN at elevated temperatures because Al₂O₃ forms a stable protective oxide at the surface above 700°C. This makes it the preferred coating for hot stamping dies and high-speed dry cutting, but in cold stamping it offers no advantage over TiCN.
• CrN has the lowest internal compressive stress of all PVD coatings (~1 GPa vs. 4–6 GPa for TiN). This makes it the best choice for large die areas where coating delamination due to stress concentration is a risk, and for thick-section punches with complex geometry.

Adhesion Failure Mechanics and Critical Thickness

Adhesion failure (coating delamination) is more common than cohesive failure in stamping applications. The critical coating thickness beyond which delamination risk increases substantially is:

t_crit = K × E_s × (1-ν²) / σ_c²

Where:

• t_crit = critical thickness (µm)
• K = adhesion constant (typically 0.3–0.5 for PVD on tool steel)
• E_s = substrate Young’s modulus (≈210 GPa for D2)
• ν = Poisson’s ratio of coating (≈0.25)
• σ_c = compressive residual stress in coating (GPa)

Example calculation for TiN on D2:

• σ_c for TiN ≈ 4 GPa
• E_s = 210 GPa
• K ≈ 0.4
• t_crit = 0.4 × 210 × (1 − 0.25²) / 4² = 0.4 × 210 × 0.9375 / 16 = 4.9 µm

Standard TiN coating thickness of 2–4 µm stays safely below this critical value. Thicker coatings require either a lower-stress alternative (CrN) or a multilayer architecture (TiN/TiAlN alternating layers at 50–100 nm periodicity) that interrupts crack propagation.

Friction Coefficient and Its Impact on Blanking Force

The tangential (friction) force on a punch during blanking is:

F_friction = μ × F_normal

During blanking, the normal force on the punch periphery is approximately equal to the blanking shear force (F_shear). For a round punch of diameter d in material of thickness t and ultimate shear stress τ_s:

F_shear = π × d × t × τ_s

For DC01 steel (τ_s ≈ 250 MPa), d = 20 mm, t = 1.5 mm:

• F_shear = π × 20 × 1.5 × 250 = 23,562 N (≈ 24 kN)

Friction force during punch penetration:

• Uncoated D2 (μ = 0.65): F_friction = 0.65 × 23,562 = 15.3 kN (total force = 38.9 kN)
• TiCN coated (μ = 0.28): F_friction = 0.28 × 23,562 = 6.6 kN (total force = 30.2 kN)
• DLC coated (μ = 0.10): F_friction = 0.10 × 23,562 = 2.4 kN (total force = 25.9 kN)

The DLC coating reduces total punch force by 33% compared to uncoated D2 in this example. On a multi-punch progressive die, this force reduction translates directly into lower press tonnage demand and reduced die set distortion.

Wear Rate Calculation Using Modified Archard’s Law

For a blanking punch operating in progressive die conditions, the volumetric wear rate is:

V_wear = k_Archard × F_N × L_slide / H_coating

Where k_Archard is the wear coefficient (dimensionless, typically 10⁻⁶ to 10⁻⁸ for PVD vs. lubricated steel sheet).

Assuming F_N = 10 kN average normal force per stroke, sliding distance per stroke L = 3 mm (die clearance × 2, plus penetration), H_TiCN = 3200 HV = 3200 × 9.81 MPa = 31,392 MPa = 31.4 GPa, and k = 5 × 10⁻⁷:

V_wear per stroke = 5×10⁻⁷ × 10,000 N × 0.003 m / 31.4×10⁹ Pa = 4.78 × 10⁻¹⁶ m³

Allowable wear volume before regrind (0.02 mm depth loss on punch face, d = 20 mm punch): V_allowable = π × (10)² × 0.02 = 6.28 mm³ = 6.28 × 10⁻⁹ m³

Strokes to regrind = 6.28×10⁻⁹ / 4.78×10⁻¹⁶ = 13.1 million strokes

Uncoated D2 with μ = 0.65 and H = 800 HV ≈ 7.8 GPa, k_Archard = 5×10⁻⁶: V_wear per stroke = 5×10⁻⁶ × 10,000 × 0.003 / 7.8×10⁹ = 1.92 × 10⁻¹⁴ m³ Strokes to regrind = 6.28×10⁻⁹ / 1.92×10⁻¹⁴ = 327,000 strokes

Ratio: TiCN extends punch life approximately 40× compared to uncoated D2 under these conditions — consistent with published production data from automotive stamping operations.

Step-by-Step Die Coating Selection Framework

Follow this sequence to select the correct coating for any stamping application.

Step 1 — Identify the dominant wear mechanism

Ask: Why does the current die fail?

• Galling / material pickup → need low friction + high hardness → DLC or TiCN
• Chipping / edge breakdown → coating may worsen the problem (adds brittleness) → fix geometry first, then consider CrN
• Abrasive wear (uniform) → need maximum hardness → TiCN or TiAlN
• Corrosion / oxidation → CrN

Step 2 — Identify sheet material

Sheet Material	Recommended Coating	Reason
Cold rolled mild steel (DC01-DC06)	TiCN	Balanced cost/performance
AHSS/UHSS (DP600-DP1200)	TiAlN or TiCN-nanocomposite	Abrasive hard phases
Galvanized / Galvalume	DLC or CrN	Zinc adhesion to TiN/TiCN is problematic
Aluminum (1xxx, 5xxx)	DLC or CrN	Al welds strongly to TiN/TiCN
Stainless steel (304, 316)	TiAlN	Austenitic work-hardening requires hardness + oxidation resistance
Copper / Brass	TiCN or DLC	Cu adhesion to TiN is severe
Silicon electrical steel	TiCN-nanocomposite	SiO₂ particles are highly abrasive

Step 3 — Check substrate compatibility

• D2 tool steel (62–64 HRC): compatible with all PVD coatings
• SKD11 (62 HRC): compatible with all PVD coatings
• M2/PM-M4 HSS (64–66 HRC): compatible with TiN, TiCN, TiAlN; excellent adhesion due to high V content
• DC53 (62 HRC): compatible with all; better toughness base for DLC
• Carbide (WC-Co): CVD preferred; PVD-TiAlN acceptable
• Nitrided surfaces: NOT compatible with PVD — nitride layer creates adhesion failure; strip before coating

Step 4 — Consider die geometry and coating thickness

Sharp edges (radius < 0.05 mm): coating builds up at edges and creates a rounded profile. For tight-radius punches, limit coating to ≤ 2 µm. If edge sharpness is critical (fine blanking), consider TiN at 1.5 µm or DLC at 0.8 µm.

Step 5 — Verify surface preparation requirements

PVD adhesion is 80% a function of surface preparation. Requirements before coating:

• Ra ≤ 0.2 µm (superfinish or fine lapping)
• Cleanliness: no oil, no rust, no EDM recast layer
• Residual stress: tensile stress from grinding must be removed by fine lapping or glass bead blasting
• EDM components: acid-etch or light polish to remove white layer before coating

Step 6 — Calculate ROI

ROI = (Extended tool life factor × Part volume) / (Coating cost + regrind cost increase)

A typical automotive blanking punch: base cost $500, regrind labor$30, coating cost $60–120 depending on vendor and complexity. If the coating extends regrind interval from 200,000 to 1,000,000 strokes (5×), regrind costs drop from$150,000/million parts to $30,000/million parts — a savings of$120,000 per million parts on a $60 investment per punch coating cycle.

Die Coating Comparison Table: All Dimensions

Parameter	TiN	TiCN	TiAlN	CrN	DLC (a-C:H)	DLC (ta-C)
Hardness (HV)	2300–2500	2800–3500	3000–3500	1800–2200	1500–3500	4000–7000
Coefficient of friction (lubricated)	0.10–0.20	0.08–0.15	0.12–0.20	0.10–0.18	0.03–0.08	0.02–0.05
Thermal stability (°C)	600	450	800	700	350	400
Typical thickness (µm)	2–4	2–4	2–5	2–6	1–3	0.5–2
Coating cost index	1.0×	1.2×	1.4×	1.3×	2.5×	4.0×
Performance vs. galvanized steel	Poor	Poor	Moderate	Good	Excellent	Excellent
Performance vs. AHSS	Moderate	Good	Excellent	Moderate	Good	Good
Performance vs. aluminum	Poor	Poor	Poor	Good	Excellent	Excellent
Adhesion to D2	Excellent	Excellent	Excellent	Excellent	Good (needs bond layer)	Moderate
Regrind compatibility	Yes	Yes	Yes	Yes	No (strip only)	No (strip only)

Common Mistakes and Failure Modes in Die Coating

1. Coating over an inadequate substrate hardness PVD coatings do not compensate for a soft substrate. If the D2 punch is at 58 HRC instead of 62 HRC (under-tempered or improperly heat-treated), the thin coating will indent under load (eggshell effect) and crack. Always verify substrate hardness with a portable Rockwell tester before sending tooling for coating.

2. Coating over EDM white layer EDM (wire EDM and die-sink EDM) produces a re-melted and requenched surface layer 5–30 µm thick that is brittle and full of micro-cracks. If PVD coating is applied over this layer, adhesion fails within 10,000 strokes. Standard fix: fine grind or lap 0.05 mm material after EDM before coating.

3. Selecting TiN for aluminum or galvanized applications Aluminum has strong chemical affinity for titanium compounds. TiN on a punch forming or blanking aluminum sheet will experience severe built-up edge (BUE) and galling within 50,000 strokes. CrN or DLC is mandatory for aluminum. Same applies for zinc-coated steel — the zinc diffuses into TiN grain boundaries at production temperatures and forms intermetallic compounds that destroy coating integrity.

4. Mismatching coating hardness to workpiece hardness The coating should be significantly harder than the workpiece (Coating HV / Workpiece HV ≥ 3 for reliable wear protection). For DP980 steel sheet (approx. 300–350 HV after forming), a TiCN coating at 3200 HV provides a ratio of ~9.5 — adequate. A CrN coating at 2000 HV provides a ratio of ~6 — borderline. For UHSS (1200 MPa+) with hardness approaching 400 HV in work-hardened regions, TiAlN or nanocomposite TiCN-Si₃N₄ is required.

5. Applying DLC to inadequately supported punches DLC is the hardest but also the most brittle and thinly deposited (0.5–2 µm) of the common coatings. Any punch that experiences impact loading (uneven cut-in, misaligned slug, double-fed sheet) will cause substrate deformation that causes immediate DLC spalling. DLC is only appropriate for punches with generous corner radii (≥ 0.1 mm), high substrate hardness (≥ 62 HRC), and clean sheet feeding.

6. Regrinding DLC-coated tooling without stripping DLC and ta-C coatings cannot be reground — the grinding heat oxidizes and destroys the carbon structure. You must chemically strip the DLC first, regrind to the required dimension, and re-coat. Using a TiCN coating is often more economical precisely because it can be reground 2–3 times before the remaining coating zone becomes thin enough to require stripping.

7. Skipping the incoming sheet material audit Coating selection assumes a known incoming material. Switching from DC04 (soft, clean surface) to DX54D+Z (galvanized) with the same TiCN-coated punch will result in zinc pickup on the punch face within 500,000 strokes. Always tie coating selection to a specific material spec, not a generic “soft steel” category.

8. Over-coating by adding new coating over existing coating without stripping Every strip-and-recoat cycle requires chemical stripping in a hydrogen peroxide or NaOH bath depending on coating type. Re-coating without stripping adds thickness, degrades adhesion at each cycle, and changes dimensional accuracy of the punch. Maximum two re-coats on TiN/TiCN without stripping; DLC always requires stripping.

Industry-Specific Applications with Production Examples

Automotive Body Panels (mild steel, AHSS)

Toyota Production System documentation specifies TiCN for all blanking punches in AHSS body panel lines. The standard is:

• Punch material: DC53 or PM-V30 (powder metallurgy)
• Coating: TiCN, 3 µm, PVD arc evaporation
• Regrind interval: 800,000–1,200,000 strokes (vs. 150,000 uncoated)
• Galling index (Japan Die Technology Association scale 1–10): < 2

For hot stamping (22MnB5 press hardening steel), TiAlN at 4–5 µm is standard because die temperatures can reach 200–300°C locally at the die face.

Electrical Motor Lamination (non-grain-oriented silicon steel)

Silicon electrical steel (e.g., 35PN300) contains 2–4% Si, which forms SiO₂ particles. These are highly abrasive against any coating. The current production standard in Japan (Mitsui High-tec, Nippon Steel tooling specs) is:

• Punch material: PM-HSS (ASP2023 or similar)
• Coating: TiCN-Si₃N₄ nanocomposite, 2–3 µm
• Regrind interval: 5,000,000–8,000,000 strokes
• Punch clearance: 1.5–2.5% per side
• Lamination thickness: 0.35 mm or 0.50 mm

The nanocomposite structure (TiCN grains 5–10 nm embedded in amorphous Si₃N₄ matrix) achieves hardness up to 4500 HV while maintaining toughness superior to conventional TiCN.

Aluminum Can Body Blanking (Food & Beverage)

Aluminum (3004-H19, 3104-H19) requires low friction and no material transfer. The industry standard:

• Punch material: D2 or carbide
• Coating: DLC (a-C:H or ta-C depending on tonnage), 1–2 µm
• Lubrication: minimal (draw compound at 0.5–1.5% concentration)
• Regrind interval: 3,000,000–5,000,000 strokes
• Part defect rate: < 50 ppm cosmetic scratches

Ball Beverage (formerly Rexnord) published production data showing DLC-coated tools at their Fairfield (California) can plant reduced aluminum pickup incidents from 1 per 200,000 cans to 1 per 2,000,000 cans — a 10× improvement.

Copper Bus Bar Blanking (Electrical Components)

Copper work-hardens rapidly and has extremely high chemical affinity for both TiN and TiCN. CrN is the coating of choice:

• Punch material: D2 (60–62 HRC)
• Coating: CrN, 4–6 µm (thicker due to lower internal stress allowing thicker deposition)
• Regrind interval: 1,000,000–2,000,000 strokes
• Burr height limit: ≤ 0.05 mm for bus bar applications requiring close electrical contact

Consumer Appliance Stampings (galvanized steel, zinc-aluminum coated)

White goods manufacturers (washing machine drums, refrigerator inner liners) use galvanized steel in 90%+ of applications. Standard practice:

• Punch material: SKD11 (D2 equivalent) or DC53
• Coating: CrN or CrCN, 3–5 µm
• Surface finish before coating: Ra ≤ 0.15 µm
• Regrind interval: 1,500,000–3,000,000 strokes

At BSH Home Appliances Cairo (comparable large-scale appliance production), transitions from TiN to CrN coatings on galvanized blank drawing tooling reduced zinc pickup defect rates by 75% and extended regrind intervals from 400,000 to 1,800,000 strokes in documented production trials.

FAQ: Die Coating for Stamping — 6 Questions Engineers Ask

Q1: My TiCN punch is only lasting 100,000 strokes before galling starts. The coating looks intact under magnification. What is happening?

The coating is likely intact but the substrate is deforming. Check your punch hardness — it may be under 60 HRC. The thin TiCN coating (2–3 µm) cannot resist contact pressures that cause plastic deformation of the substrate beneath it. The “eggshell” effect: coating remains whole but the substrate indents. Solutions: (1) upgrade substrate to 62–64 HRC via proper heat treatment, (2) switch to PM-HSS with higher base hardness, (3) re-examine die clearance (tight clearance increases contact pressure dramatically).

Q2: We run both galvanized and uncoated cold rolled steel on the same die set. Which coating do we use?

CrN. It performs acceptably against both materials. TiCN would be better against uncoated CR steel, but the zinc adhesion problem makes it unacceptable for the galvanized runs. DLC would be better against galvanized, but the cost premium and inability to regrind make it impractical for a shared die set. CrN is the compromise solution — expect 60–70% of TiCN’s wear resistance on CR steel and excellent zinc resistance on galvanized.

Q3: What is the correct surface roughness specification before PVD coating?

Ra ≤ 0.2 µm for standard PVD (TiN, TiCN, TiAlN, CrN). Ra ≤ 0.05 µm for DLC ta-C (ultra-smooth is required because the thin DLC layer follows the substrate topography exactly). Coarser surfaces do not get “filled in” by the coating — the coating uniformly follows the surface asperities. A Ra 0.4 µm surface will have Ra ≈ 0.4 µm after TiN coating. For critical forming surfaces, fine lap after grinding before coating.

Q4: Can we coat a worn punch instead of regrinding first?

No. A worn punch has dimensional loss (typically 0.02–0.05 mm at the cutting edge). PVD adds only 2–5 µm. Coating a worn punch does not restore its dimensions. You must regrind to restore geometry, then coat. Coating over wear craters also results in poor adhesion in the recessed areas and premature spalling.

Q5: We’re considering a TiN coating supplier who offers coating at 400°C PVD temperature. Our D2 punches are tempered at 180°C. Will the coating process soften them?

Potentially, yes. D2 at 62 HRC is typically double-tempered at 160–200°C. A PVD process at 400°C would be a third temper and would reduce hardness by approximately 2–4 HRC points (to 58–60 HRC). This is acceptable for some applications but not ideal. Specify that coating temperature must not exceed 180°C, or alternatively retemper after coating at 180°C to restore surface hardness. Better: select a supplier whose PVD runs at 150–200°C. Low-temperature PVD processes are well-established.

Q6: What is the difference between monolayer TiCN and nanocomposite nc-TiCN/a-Si₃N₄? Is the price premium worth it?

Monolayer TiCN (columnar grain structure) has hardness of 2800–3500 HV. Nanocomposite TiCN-Si₃N₄ (5–10 nm TiCN crystals in amorphous Si₃N₄ matrix) reaches 4000–4500 HV. The Si₃N₄ matrix also inhibits grain boundary diffusion, raising thermal stability to 600°C vs. 450°C for standard TiCN. For AHSS blanking and silicon steel lamination, the price premium (typically 30–50% over standard TiCN) delivers tool life increases of 2–3× over standard TiCN. For mild steel blanking, standard TiCN is adequate and the nanocomposite premium is not recovered.

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Conclusion: Die Coating Selection is a Process Decision, Not a Procurement Decision

Die coating selection belongs in the process engineering workflow — alongside die design, material selection, and press setup. The decision tree is short: identify failure mode, match sheet material to coating chemistry, verify substrate compatibility, and confirm surface preparation protocol. Every coating choice that deviates from this framework will either underperform (TiN on galvanized) or fail catastrophically (DLC on a soft substrate).

The economics are equally clear. PVD coatings cost between $0.60 and$6.00 per cm² of coated surface, with TiN at the low end and DLC ta-C at the high end. A standard blanking punch costs $30–100 in coating fees. Given that a properly selected coating extends regrind intervals by 3–10× and eliminates galling-related line stoppages, the payback period on any coating investment is measured in weeks, not years.

The practical hierarchy for most automotive and appliance stamping operations is: TiCN as the default for CR steel → CrN for galvanized or mixed material → DLC for aluminum or maximum die life requirements → TiAlN for AHSS/UHSS or elevated temperature applications.

Demirezen Engineering provides die coating consultation and vendor qualification services for stamping operations in Turkey, Egypt, and the Gulf region. If you are evaluating coating suppliers, struggling with galling on AHSS tooling, or designing tooling for a new material, contact us directly.

Demirezen Engineering WhatsApp: +90 543 341 6183 Website: demirezenengineering.com

Internal Link Suggestions

• Tool Steel Selection for Stamping Dies: D2, SKD11 and Powder Metallurgy Grades
• Die Failure Analysis: Chipping, Galling and Cracking — Root Causes and Prevention
• Blanking Die Clearance Calculation by Material Type and Thickness
• Fine Blanking vs Conventional Blanking: Process Differences, Tooling and Economics
• Stainless Steel Stamping: Tooling, Lubrication and Springback Management

External Reference Sources

• Subramanian, C. & Strafford, K.N. (1993). Review of multicomponent and multilayer coatings for tribological applications. Wear, 165(1), 85–95. [Elsevier]
• Mayrhofer, P.H., Mitterer, C., Hultman, L. & Clemens, H. (2006). Microstructural design of hard coatings. Progress in Materials Science, 51, 1032–1114.
• Society of Manufacturing Engineers (SME). Die Design Fundamentals, 3rd Edition. Dearborn, MI: SME Press.

Suggested Images and Diagrams

1. Figure 1 — PVD Coating Hardness vs. Temperature Chart: Bar chart comparing hardness at 25°C, 300°C, 500°C, and 700°C for TiN, TiCN, TiAlN, CrN, and DLC. ALT: “PVD coating hardness vs temperature chart for TiN TiCN TiAlN CrN DLC stamping dies”

2. Figure 2 — Coating Selection Decision Tree: Flowchart: Sheet material type → Failure mode → Coating choice → Substrate check → Surface prep requirement. ALT: “Die coating selection flowchart for stamping press tooling”

3. Figure 3 — Cross-section Micrograph Comparison: SEM cross-section showing TiCN columnar grain structure (monolayer) vs. nanocomposite nc-TiCN/Si₃N₄ grain structure. ALT: “SEM cross section TiCN monolayer vs nanocomposite die coating stamping”

4. Figure 4 — Wear Track Comparison: Pin-on-disk wear track optical microscopy: uncoated D2 vs. TiCN vs. DLC at same load and sliding distance. ALT: “wear track comparison D2 uncoated vs TiCN vs DLC die coating stamping punch”

5. Figure 5 — Strokes to Regrind by Coating and Material: Bar chart: strokes to regrind for each coating/material combination (DC01, DP600, galvanized, aluminum). ALT: “punch regrind interval by coating type stamping die life comparison”