Bolt Carrier Group Coatings
Cryptic Coatings specializes in complete bolt carrier groups coated in one of six available coatings each designed to provide reduced friction coefficient that not only lowers operating temperatures but also increases overall performance and BCG life. Back by a lifetime guarantee, we are confident that our coated BCGs will increase lubricity and wear resistance while providing a smoother recoil, improved consistency, faster cyclic rates and reduce carbon fouling.
The PVD & CVD Processes
What is PVD?
PVD is the abbreviation of Physical Vapor Deposition. PVD is a process that produces a family of coatings. The staple of the family is titanium nitride (TiN) however: chromium nitride (CrN), aluminum titanium nitride (AlTiN) are other examples of PVD coatings. This technology gained popularity in the 70’s when the military adapted it to solve a wide range of issues regarding friction and wear of metal parts. The term physical vapor deposition was first used in 1966 but the process can be traced back as far as 1838 to a scientist named Michael Faraday. The most current version of physical vapor deposition was completed in 2010 by NASA scientists at the NASA Glenn Research Center in Cleveland, Ohio. The process is carried out in high vacuum chambers, well below atmospheric pressures.
How does the PVD process work?
Parts are sealed in an air tight chamber that is pumped down several atmospheres. A negative voltage applied to the parts attract the positive ion molecules bombarded from hard targets (i.e. titanium, chromium etc.). This bombardment is a high-power electric arc that produces a highly ionized vapor. At the same time, a reactive gas (i.e. nitrogen or a gas containing carbon) is introduced; it forms a compound with the metal vapor and is deposited on the parts as a thin, highly adherent coating. In order to obtain a uniform coating thickness, the parts are rotated at uniform speed about several axes.
What is CVD?
CVD is the abbreviation Chemical Vapor Deposition. Chemical vapor deposition is a chemical process used to produce high-purity, high-performance solid materials. One such material is Diamond-Like-Carbon (DLC). Since 1952 when William Eversole grew the first diamond in a vacuum chamber, DLC thin film use has grown tremendously. DLC coatings feature excellent hardness, wear and low friction properties under dry or deficient lubrication conditions. They are ideally suited for mechanical assemblies with sliding and rolling movements
How does the CVD process work?
Parts are sealed in an air tight chamber that is pumped down several atmospheres. Then a high-frequency voltage is applied and gases containing significant amounts of sp3 are introduced. This creates carbon and hydrogen atoms that form a dense coating on the parts.
Why use PVD or CVD?
- First off the surface is very hard and smooth making it an extremely high wear resistance coating.
- The friction coefficient is greatly reduced requiring less lubrication.
- Operating temperatures are lowered.
Yes you can run without lubrication when it’s necessary but its good practice to use a small amount of oil whenever allowable.
Black Nitride Process
Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to improve the surface priorities of the metal. There are three common types of nitriding. Salt Bath, Gas and Plasma nitriding.
Salt bath nitriding process sometimes referred to as “Black Nitride”, Melonite or liquid nitriding is widely used in the firearms industry. Case hardening is the usually the primary benefit of the process. The “black” appearance is a result of the nitriding process.
Black Nitride liquid salt bath is maintained between 500 – 630°C (930 – 1165°F). Nitrogen-bearing salts produce a controlled and highly uniform release of nitrogen at the interface of the workpiece. Nitrogen diffuses into, and chemically combines with, nitride-forming elements in the metal. Through a catalytic reaction, this produces a tough, ductile compound layer with exceptional engineering and wear properties.
Benefits of Black Nitride:
- Improved wear resistance (case hardened to 55 HRC)
- Improved friction properties (0.45 CoF)
- Anti-scuffing/seizure protection Excellent corrosion protection
- Good surface fatigue resistance
- Enhanced corrosion resistance
- Uniform black surface