PVD Coating
PVD coating vaporises a solid target inside a vacuum chamber so it condenses on the part as a very thin, extremely hard film.
- Part
- Finishing
- Revised
- 2026-08-11
At a glance
- Family
- Additive
- Typical tolerances
- Adds 0.5–5 µm (0.00002–0.0002 in) per surface — dimensionally negligible for most fits; thicker tooling coatings at 4–5 µm should be checked on close-fitting punch and die clearances
- Surface finish
- Fully conformal — reproduces the incoming finish; arc-deposited films raise Ra slightly, sputtered films less so
- Typical volumes
- 1 part to high volume; cost per part is governed by how densely the chamber can be loaded
- Lead time
- 3–10 business days at a coating service; cycle time itself is 2–6 hours
- Materials
- Metal, Plastic, Glass, Ceramic
What it is
Physical vapor deposition converts a solid target material into vapor inside a vacuum chamber and condenses it on the part as an extremely thin, extremely hard ceramic film. Typical coatings are 0.5–5 µm (0.00002–0.0002 in) thick — thin enough that the part comes out of the chamber dimensionally as it went in, and thin enough that it reproduces the incoming surface finish exactly.
The industrial value is hardness: TiN is commonly quoted near 2,300 HV, TiCN near 3,000 HV, and TiAlN near 3,300 HV, against roughly 900 HV for hardened tool steel. Those numbers, plus service temperatures of 600 °C (1,110 °F) for TiN and around 800 °C (1,470 °F) for TiAlN, are why PVD dominates cutting tool and injection mold coating. The same process in thinner decorative films gives the gold, bronze, black and gunmetal finishes on hardware, watches and firearms. The main constraints are line-of-sight deposition, a process temperature that must sit below the substrate's tempering temperature, and batch-based economics.
How it works
- Prepare the surface. PVD adds no thickness and hides nothing, so the substrate must already be at its final finish and must be metallurgically clean. Grinding, polishing or lapping comes first. EDM white layer, residual plating, oxide, and any organic residue must be removed — adhesion failures nearly always trace to this step.
- Clean. Multi-stage ultrasonic aqueous or solvent cleaning followed by vacuum drying. Fingerprints deposited after cleaning are enough to cause flaking.
- Load and pump down. Parts are fixtured on planetary rotation so every surface presents to the source, then the chamber is evacuated. Pump-down alone takes a significant fraction of the cycle.
- Heat and ion-etch. The load is heated, typically to 400–500 °C (750–930 °F) for arc processes, and bombarded with ions to sputter-clean the surface at the atomic level and improve adhesion. Low-temperature processes below about 250 °C (480 °F) exist for substrates that cannot take the heat.
- Deposit. In cathodic arc evaporation, an arc vaporizes and ionizes the target; in magnetron sputtering, ions knock atoms off the target. Reactive gas — nitrogen for nitrides, acetylene for carbides — is bled in to form the compound on the part. Deposition rates give 0.5–5 µm over roughly 1–4 hours.
- Cool and unload. Total cycle is typically 2–6 hours including pump-down and cooling, and the whole chamber load shares that cycle.
Arc versus sputtering
Cathodic arc gives high ionization, excellent adhesion and fast deposition, but ejects micro-droplets that leave the surface slightly rougher than it went in. Magnetron sputtering is smoother and better for decorative and optical work, at lower deposition rates. Choose arc for tooling, sputtering where the appearance of the finished surface is critical.
Design guidelines
The substrate must be finished before coating
At 0.5–5 µm the film is fully conformal. Every scratch, tool mark, EDM texture and polish line comes through unchanged, and arc-deposited films slightly increase Ra. If the requirement is a mirror mold surface with a hard coating, polish to that finish first — see the surface finish chart for the Ra achievable by each prep method.
Check the substrate's tempering temperature
Arc PVD at 400–500 °C (750–930 °F) will over-temper any steel tempered below that. High-speed steels tempered around 540 °C (1,000 °F) are safe. Through-hardened tool steels tempered at 200 °C, precipitation-hardened stainless in certain conditions, and most aluminum are not — those need a low-temperature process below roughly 250 °C (480 °F), which typically trades away some hardness and adhesion.
Design for line of sight
Vapor travels in straight lines. Deep bores, blind holes, undercuts and the inside of tubes coat thin or not at all, even with planetary rotation. As a working rule, expect good coverage down to about one diameter into a hole and progressively less beyond that. Where an internal surface must be coated uniformly, electroless nickel or a CVD process is the better answer.
Do not use PVD to fix dimensions or fill defects
Unlike hard chrome, PVD cannot be used to build a worn surface back up. It is a surface property modification, not a repair.
Provide fixturing features
Parts must be held without shadowing the coated surface, and the fixture contact point is uncoated. On tooling, that is usually the shank or a bore. On decorative parts, designate an acceptable contact area.
Match the coating to the duty
TiN (gold, ~2,300 HV, to about 600 °C) is the general-purpose choice. TiCN (~3,000 HV) is harder and tougher for interrupted cuts and forming tools. TiAlN/AlTiN (~3,300 HV, to about 800 °C) forms a protective alumina layer at high temperature and is the standard for dry and high-speed machining. CrN is more corrosion resistant and less brittle, used on molds and forming dies. DLC gives a very low coefficient of friction for sliding and non-stick applications.
| Feature | Recommended | Limit | Why |
|---|---|---|---|
| Coating thickness | 2–4 µm on tooling; 0.25–1 µm decorative | 5 µm | Thicker films become brittle and lose adhesion |
| Incoming surface | Final finish, fully cleaned | — | The film is conformal and hides nothing |
| Substrate temper | Above the process temperature | 400–500 °C (750–930 °F) for arc PVD | Coating cycle will over-temper softer-tempered steels |
| Bore coverage | ~1 diameter deep | — | Line-of-sight deposition |
| Fixture contact | 1 designated uncoated area | — | The part must be held somewhere |
| Chamber utilization | Fill the load | — | Cost is per cycle, not per part |
Cost drivers
PVD is billed per chamber cycle, not per part. A 2–6 hour cycle costs the same whether the fixture holds twelve parts or twelve hundred, so the single largest lever is load density.
- Chamber utilization. Small parts that fixture densely coat at a low unit cost. A single large part occupying a whole chamber carries the entire cycle.
- Substrate preparation. Polishing, lapping and cleaning to PVD standards frequently cost more than the coating cycle itself, and are non-negotiable.
- Coating chemistry. TiN is the least expensive. Multilayer, nanolayer, AlTiN and DLC coatings need longer cycles and more expensive targets.
- Fixturing. Custom fixtures for planetary rotation are tooling, amortized over the program.
- Requalification and stripping. Recoating worn tools requires stripping the old coating chemically, which is an extra operation and can attack the substrate if repeated too often.
Cost-reduction tactics:
- Batch parts so the chamber runs full — this dominates every other cost factor.
- Specify the incoming Ra you actually need; polishing beyond the functional requirement is wasted money.
- Use TiN unless the temperature or wear duty genuinely requires an aluminum-bearing or DLC coating.
- Standardize fixturing across a family of parts so one fixture serves many programs.
- Where a deep internal surface needs coating, price electroless nickel against PVD before committing — line-of-sight limits may make PVD unusable at any price.
Questions
6 questionsHow thick is a PVD coating?
Typically 0.5–5 µm (0.00002–0.0002 in). Cutting tools and molds are usually coated at 2–4 µm; decorative finishes at 0.25–1 µm. At those thicknesses the coating is dimensionally negligible for most fits and reproduces the underlying surface finish exactly.
How hard is PVD coating?
Common tool coatings are quoted near 2,300 HV for TiN, 3,000 HV for TiCN and 3,300 HV for TiAlN, against roughly 900 HV for hardened tool steel. Maximum service temperature also varies by chemistry — about 600 °C (1,110 °F) for TiN and about 800 °C (1,470 °F) for TiAlN.
Will PVD coating damage my heat-treated part?
It can. Cathodic arc PVD runs at 400–500 °C (750–930 °F), which over-tempers any steel tempered below that. High-speed steels tempered around 540 °C (1,000 °F) are safe. For substrates that cannot take the heat, low-temperature processes below roughly 250 °C (480 °F) are available, usually with some loss of hardness and adhesion.
Can PVD coat the inside of a hole or tube?
Poorly. Deposition is line-of-sight, so coverage drops off rapidly beyond about one diameter into a hole and blind pockets and undercuts may not coat at all. Where an internal surface needs uniform coverage, electroless nickel or a CVD process is the appropriate choice.
Does PVD hide scratches or improve surface finish?
No. At a few microns the film is fully conformal, so every scratch, tool mark and polish line shows through, and arc-deposited coatings raise Ra slightly. The substrate must be brought to its final finish before coating.
Which PVD coating should I choose for cutting tools?
TiN is the general-purpose default. TiCN is harder and tougher for interrupted cuts and forming. TiAlN or AlTiN forms a protective alumina layer at high temperature and is standard for dry and high-speed machining. CrN suits molds and forming dies where corrosion resistance and toughness matter more than peak hardness.