Should You Coat Your Production Parts? A PVD & DLC Decision Guide for Manufacturers

What PVD and DLC coatings actually are

PVD — physical vapor deposition — grows a thin ceramic film directly onto your part inside a vacuum chamber. A metal source is vaporized, reacts with a process gas, and condenses on the part surface as a hard nitride: AlTiN, TiN, or TiCN, depending on the recipe. DLC (diamond-like carbon) is the other family: an amorphous carbon film that behaves like a permanently slick, hard skin. These are not paints or platings — the film is bonded to the substrate at the atomic level, so it doesn't chip or peel the way a sprayed finish can.

Two properties make these films worth a manufacturer's attention. First, they are hard — from 2,000 HV for DLC up to 3,300 HV for AlTiN, far harder than any hardened steel your part is made from. Second, they are thin: 1 to 4 microns, roughly 0.00004" to 0.00016" per surface. That thinness is the point. A coated part still gauges, threads still fit, and a tight-tolerance assembly almost never needs redesign to accept a coating. You get a working surface harder than the part itself without changing the part.

One clarification worth making, because the names are close: PVD and DLC films are applied by Crystallume PVD, co-located with RobbJack in Lincoln, California. Our Crystallume facility in Santa Clara applies only CVD diamond coating — a much thicker crystalline diamond film used on tools for graphite and composites, and a different conversation from the one in this guide.

Which parts benefit — and why manufacturers coat them

The parts that pay back a coating share a pattern: a surface doing hard work — sliding, wearing, corroding, or being looked at — on a part whose geometry you don't want to change.

• Sliding interfaces and wear surfaces. Firearms slides and bolt carriers are the textbook case: steel on steel, thousands of cycles, run dirty and under-lubricated. DLC's coefficient of friction of 0.05–0.15 is a fraction of bare steel's — the action runs smoother, resists galling, and carbon fouling wipes off a slick surface instead of baking onto a rough one.
• Corrosion plus cosmetics. The deep, even black of DLC is a genuine reason firearms and knife brands choose it — it's a working finish, not just protection. The dense film also acts as a corrosion barrier for handling, sweat, and weather exposure. Be realistic here: a DLC-coated carbon-steel blade resists corrosion far better than bare steel, but a micron-thin film doesn't turn carbon steel into stainless.
• Knife blades and hardware. A film several times harder than the blade steel supports the edge region against abrasive wear and keeps the flats scratch-resistant. G10 grips and other composite furniture are a different story — these films are for metal substrates, so grip hardware gets coated, not the G10 itself.
• Molds, dies, and tooling components. TiN has decades of history on injection molds for release and wear; TiCN's toughness suits forming punches and dies; DLC stops aluminum and plastics from sticking to cores and pins. Because the film is microns thick, cavity dimensions and polish are preserved — a mold surface goes in polished and comes out polished, in gold or black.
• High-volume production hardware. Pins, cams, followers, latches, valve components — anywhere a small part wears against another and warranty or service life is the cost driver. At production quantities, coating becomes a per-part line item that's easy to justify against returns.
• Investment castings and 3D-printed metal parts. Both coat well when the surface is dense and clean. Surface condition is the variable — porosity and rough as-printed texture show through a conformal film — so these parts in particular benefit from a sample-first conversation.

PVD vs DLC: choosing by what the surface has to survive

The film choice follows the dominant demand on the surface — wear, friction, appearance, or temperature. The four films each have a lane:

• AlTiN (violet-black, 3,300 HV, service to 900 °C) — the hardness and heat champion. Choose it for surfaces that run hot or fight abrasive wear: high-temperature hardware, hot-working tooling, wear parts in gritty environments.
• TiCN (gunmetal grey, 3,200 HV, service to 400 °C) — hardness plus toughness for impact and abrasion at moderate temperature: punches, forming dies, shear surfaces, heavily loaded wear parts.
• TiN (gold, 2,800 HV, service to 600 °C) — the proven all-rounder, and the only one that's gold. General wear resistance, mold surfaces, decorative-plus-functional hardware. When appearance calls for gold, this is the answer.
• DLC (black, 2,000 HV, coefficient of friction 0.05–0.15, service to 450 °C) — the friction specialist. Choose it when the surface slides, when material wants to stick or gall, or when the product has to be a true deep black. This combination is why it dominates firearms and knife work.
• Where neither pays — and we'll tell you when this is your situation: a part that fails by bending, denting, or gross wear-through (a micron-thin film can't reinforce a soft substrate — that's a heat-treat or material problem); a part that only needs corrosion protection in severe exposure (plating or stainless is the cheaper fix); or a surface that needs thick dimensional build-up, which is hard-chrome or thermal-spray territory, not thin-film.

What a coating house needs from you

A good coating outcome is decided before the parts ever enter the chamber. When you talk to the applications team, have answers to four things:

• Material and condition. Hardened steels, stainless, tool steels, and titanium all coat well. A hard film performs best on a hard substrate — think of ice on a lake versus ice on a pond of slush — so a hardened or nitrided part gets far more from a coating than a soft one. Prior surface treatments matter too: bluing, black oxide, anodize, or plating on the surface changes the prep conversation, so tell us what's already on the part.
• Heat-treat state and temperature limits. Deposition happens at elevated temperature, and the process gets matched to what your part can tolerate — a part tempered at low temperature, or an age-hardened alloy, needs that conversation up front so the coating never costs you the hardness you paid for. DLC in particular can be applied at comparatively low temperature, one more reason it's the default on finished, heat-treated firearms components. Tell us the alloy and the heat-treat spec; we'll tell you what's compatible.
• Masking and line-of-sight. PVD is a line-of-sight process: exterior surfaces coat beautifully, deep bores and internal passages see less film. Surfaces that must stay bare — a bore you'll lap, a press-fit seat, a weld zone — get masked, and every masked feature adds fixturing work. Flag them on the print.
• Surface finish and volumes. The film replicates the surface underneath it, at 1–4 microns thick: polish goes in, polish comes out; bead-blast matte stays matte; machining marks and porosity show through. Decide the finish you want the customer to see, and put it on the part before coating. And bring your real volumes — recurring lots of 50 to 300 parts a month are exactly the work these production lines are built around, and recurring work lets fixturing and racking be engineered once and amortized across every lot.

How to start: sample parts first, production after proof

Don't start with a purchase order — start with sample parts. Send a few representative pieces in their production heat-treat and finish, tell us how the part lives (what it slides against, what it's exposed to, what failure looks like today), and the applications team will recommend a film, flag any substrate or masking concerns, and coat the samples so you can test them in the real assembly. Validate on your bench and your torture test, not our word. When the samples prove out, the same recipe, fixturing, and process run your production lots.

Talk to your RobbJack representative, reach us through the contact page at robbjack.com/contact, or call (800) 527-8883. The coating operation itself lives at crystallumepvd.com — same campus, same team, purpose-built production coating lines in Lincoln, California.