Every coated part that fails in the field can usually be traced back to a mismatch between the coating's properties and the application's actual demands. Not a defective coating. Not a bad substrate. A selection problem.
At Advanced Coating Technologies, we see this pattern: an engineer or buyer specifies a coating based on familiarity or habit, and the part comes back worn, delaminated, or underperforming within weeks. The fix is almost always the same: go back to the data and match three measurable properties to the operating conditions.
Those three properties are hardness, thermal stability, and friction. Get them right, and the coating protects the part for its full intended service life. Get any one of them wrong, and the coating becomes the weak link.
Hardness determines how well a coating resists material loss from abrasion, erosion, and contact pressure. It is measured on the Vickers scale (HV), and in PVD and DLC coatings, values range from 600 HV on the low end to 4,500 HV at the top.
The mistake we see most often is assuming harder is always better. A 4,500 HV coating like WARRIOR or nACO is built for hardened steels and aggressive dry milling, not for a sliding bearing that fails from galling rather than abrasion. Conversely, applying a general-purpose TiN (HV 2,400) to a carbide end mill cutting hardened steel above 50 HRC leaves performance on the table when AlTiSiN (HV 4,500) is designed for exactly that condition.
Hardness should be matched to the dominant wear mechanism in your application:
As a high-strength coating provider, we help our customers match hardness to the actual failure mode, not just the highest number on the spec sheet.
Every coating has a ceiling. Push a part beyond its coating's max working temperature, and the film begins to oxidize, soften, or lose adhesion. In aerospace, automotive, and high-speed machining environments, thermal stability is often the property that separates a coating that lasts from one that fails early.
Here’s where the numbers matter. Our coating guide lists max working temperatures for every coating we apply:
For high-temperature PVD coatings for jet engine components such as bearings, gears, valves, and precision mechanisms operating in high-temperature environments, thermal stability is non-negotiable. Parts exposed to sustained heat, thermal cycling, or proximity to combustion zones need coatings that perform at operating temperature, not just on a room-temperature test bench. A coating that holds its hardness at 25°C but oxidizes at 650°C offers no protection to a component cycling between those extremes throughout its service life. This is why the max working temperature is a spec to verify against your actual operating conditions, not a number to glance at and assume will hold.
The coefficient of friction (COF) measures how much resistance a coated surface generates during contact with another surface. Lower COF means less friction, less heat generation at the contact point, and less energy lost to resistance.
Friction is the property that gets overlooked most often in coating selection, particularly in non-cutting applications. Engineers focus on hardness and temperature, but for components that slide, rotate, or cycle against mating surfaces, COF is frequently the determining factor in service life.
Our coatings span a wide COF range:
In automotive drivetrain and valve-train applications, switching from a standard PVD coating to a low-friction coating like DLC reduces energy loss at every moving interface. In firearms, DLC on slides and bolt carriers means smoother cycling, less fouling, and reduced cleaning frequency. In medical instruments, low COF supports smoother operation during procedures and helps maintain surface integrity through repeated sterilization.
Friction isn’t a secondary property. For a large category of coated components, it’s the property that determines whether the part performs or disappoints.
These three properties, hardness, thermal stability, and friction, aren’t independent choices. They interact. A coating with extreme hardness but high friction generates more heat at the contact surface, which can push the part past the coating's thermal limit. A low-friction coating applied to a part that exceeds 300°C will degrade regardless of how smooth it runs at room temperature.
The right approach starts with the operating conditions:
Once those questions are answered with specifics, the coating selection becomes a data-driven decision rather than a guess.
At ACT, our team reviews these variables with you before recommending a coating. We use in-house Tribo Meters, Calo Testers, Fisherscope X-ray systems, and optical microscopes to verify that what we apply matches what the application demands. That process, backed by AS9100D and ISO 9001:2015 documentation, is how coated components survive in service instead of coming back as warranty claims.
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