Hard Coatings

Hard coatings add ultra-thin, wear-resistant layers like DLC, TiN, or TiAlN to boost surface hardness, reduce friction, and extend part life.

Overview

Hard coatings are ultra-thin, engineered surface layers—typically applied by PVD or CVD—to dramatically increase hardness, wear resistance, and often lower friction. Common coatings like DLC, TiN, and TiAlN bond tightly to metals, carbides, and some alloys without changing the bulk properties or geometry significantly.

Use hard coatings when your machined parts, tools, or molds see sliding contact, abrasion, or high-cycle loading and you need longer life without redesigning the base material. They are ideal for cutting tools, dies, high-performance mechanical components, and precision parts where you cannot afford distortion from heat treatment. Tradeoffs include added process cost, line-of-sight limitations, tight fixturing requirements, and the need for good base surface finish—coatings do not hide roughness or defects. Coating thickness is small but must be accounted for on tight fits, and not all materials or operating temperatures suit every coating type.

Common Materials

  • Tool steel H13
  • Tool steel D2
  • Carbide
  • Stainless steel 17-4
  • Titanium Grade 5
  • Aluminum 6061

Tolerances

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Applications

  • Carbide cutting inserts and end mills
  • Injection mold cavities and cores
  • Punches, dies, and forming tools
  • Hydraulic and pneumatic shafts
  • Piston pins and engine valve components
  • Firearm slides and bolt carriers

When to Choose Hard Coatings

Use hard coatings when you need a thin, hard, low-friction surface to extend wear life without changing the part’s core material or dimensions significantly. They suit precision, high-value parts and tools that see repeated contact, abrasion, or sliding, especially where distortion from through-hardening or bulk heat treatment would be a problem.

vs Machined Surface Finishing

Choose hard coatings when the base material and machined finish alone cannot deliver the wear life or friction performance you need. Machining can improve geometry and roughness, but a hard coating adds a fundamentally different surface chemistry and hardness without more material removal or geometry changes.

vs Polishing

Use hard coatings instead of relying solely on polishing when low friction and appearance are not enough and you need real gains in wear resistance and service life. Polishing improves Ra and reduces asperities, while a hard coating creates a high-hardness, engineered tribological surface over that polished base.

vs Coatings

Pick hard coatings over conventional coatings (like paint, basic platings, or soft films) when the primary requirement is wear resistance, hardness, and low friction under load. General coatings focus on corrosion protection or cosmetics; hard coatings are engineered for high-contact, high-cycle mechanical performance.

vs Heat Treatment

Use hard coatings when you cannot risk part distortion, dimensional shift, or brittleness that can come with through-hardening or case hardening. The coating hardens only the surface while the core retains toughness, which is critical for precision tools, thin sections, and tight-tolerance assemblies.

Design Considerations

  • Specify which surfaces require coating and which must be masked; include drawings or models highlighting coated areas
  • Call out pre-coating surface finish (Ra) requirements, since the coating will replicate, not improve, the underlying texture
  • Account for coating thickness in tight fits such as bores, shafts, and precision sliding interfaces
  • Avoid sharp edges and burrs; break edges lightly so the coating can adhere uniformly and resist chipping
  • Select coating type based on operating temperature, contact type (sliding vs impact), and environment (dry, lubricated, corrosive)
  • Group parts by material, size, and coating type to reduce setup cost and make batch coating economical