Why be concerned about camshaft and lifter wear surfaces?
In a high performance or racing engine, the interface between camshaft lobes and lifter faces is one of the highest for application pressures. This becomes a critical factor in the wear of mechanical camshaft lobes and non-roller lifters. Such contact stresses become more problematic when the theoretical line contact between a flat camshaft lobe and follower involves a spherical surface, as found in some racing camshaft applications. Add camshafts with lobe nose angles designed to aid lifter rotation, and the frictional loads imposed between a camshaft and its followers demand special attention to wear surfaces. It is because of these and related reasons that COMP Cams® elected to pursue what are literally state-of-the art techniques that address not only the camshaft break-in period but are directed to long use-life of the parts.
What is nitriding?
Nitriding typically has a surface layer thickness that is about one-tenth of the thickness of carburizing, but it exhibits a number of superior wear-enhancing features, including the fact that treated surfaces are much harder. In its simplest form, nitriding is a process by which nitrogen is introduced into iron or steel, causing a material’s surface hardness to be increased for improved initial and long-term wear characteristics.
The process consists of heating the subject material in a container through which nitrogen is forced to pass, thereby causing an infusion of nitrogen molecules (in a specific molecular arrangement) on and into the treated material’s surface. This creates a case-hardened condition that improves both the lubricity and wear resistance of the material. Of the four types of nitriding processes in use today (gaseous, salt bath, plasma and pulsed plasma), COMP Cams® selected the “pulsed plasma” method as superior for their products.
Specific to the COMP® approach to nitriding, the overall ammonia “composite” gas (as comprised of the individual gasses required for the process) is broken down into three different compounds to enhance the overall nitriding process. By doing so, and in conjunction with temperature control within the processing container, the parent material is conditioned for the embedding of nitrogen molecules during bombardment. During the ensuing chemical reaction that occurs, nitrogen molecules are electrically accelerated by the pulsed plasma process.
Why did COMP® elect to use the pulsed plasma method?
The facts are clear. Specifically, the pulsed plasma method of nitriding can be described as follows: Nitrogen gas is passed through a temperature-controlled chamber containing camshafts and lifters. So-called “nitrogen needles” impinge the subject material, causing a metallurgical restructuring to a depth of up to 0.010-inch. This impingement creates an overall “smoothing” effect that nets reduced sliding friction and improved wear resistance. Lubricity is also increased, a result of a decrease in friction. The very nature of this process requires that all initial machining, stress relieving, hardening and material tempering be conducted prior to applying the nitriding process.
As compared to the traditional plasma process, pulsed plasma incorporates a pulsing of the electrical current as it passes through the processing container and onto parent materials. This method of nitrogen application appears to enhance the flow of nitrogen into the parent material, resulting in a higher degree of content and surface hardness. Applied at a lower processing temperature, pulsed plasma allows finished parts to be produced with less dimensional distortion and overall strength reduction, both of which help extend the usage life of treated components. Actually, lower application temperatures and less localized heating at the edges of parts are the main benefit of pulsed plasma. This technique also works better with complex geometries because, between pulses, the nitrogen is allowed to flow into tighter spaces.
Technically speaking, the pulsed plasma process is most appropriately applied to high-carbon steel alloys, especially cast-iron material of the type COMP® uses for their flat tappet camshafts. Materials selected for these components are only those most benefitting from the pulsed plasma method.
To the point, the pulsed plasma process produces three layers of re-defined metallurgical structure. The metallurgical properties of these layers all exhibit an arrangement of carbon molecules that result in a level of wear resistance and surface lubricity that is superior to other methods of extending camshaft/lifter use life.
It is also important to note that COMP Cams® has previously investigated and used other methods of extending the life of camshafts that have proven to be successful in past years. In fact, salt bath nitriding is one form of increasing the surface hardness and wear resistance of these type parts. This method, although beneficial in certain types of camshaft applications, was discontinued in favor of the pulsed plasma process. Of the reasons underlying this decision, the pulsed plasma method provides an extended range of benefits, including resistance to the spalling or metal flaking type of failures sometimes associated with roller tappet camshafts and the deepest treatment penetration.
Bottom-line benefits to users of COMP Cams®
Ample evidence exists in support of why camshafts subjected to the pulsed plasma nitriding process are superior to all others. In the testing laboratory, on the dyno or in racing engines of the most demanding and hostile operating environments, data indicates reduced component wear, particularly when using sliding-friction tappets. This is true, regardless of basic tappet design.
Wear surface hardness is also increased, on the order of values in the range of 55-70 on the Rockwell “C” scale. As previously indicated, the pulsed plasma process tends to “fill in” slight wear surface imperfections (prior to parts use) that reduce friction, further extending parts life and enhancing the effectiveness of lubricants. This “surface improvement” actually occurs as the part is bombarded with nitrogen. As compared to micro-peening where smaller shot is used for a better surface, pulsed plasma nitriding could be considered as chemically shot-peening the surface (on the atomic level).
Finally, and also along the lines of reduced component wear, the pulsed plasma process reduces (typically eliminates) problems associated with “micro welding,” the combined result of wear surface fracture and material disruption traceable to both high temperature and impact stress loads at the camshaft lobe and lifter interface.
COMP Cams® has, through a rigorous process of exploring and applying the most recent technologies that can extend the life of camshaft lobes and lifter faces, demonstrated its long-term intent to bring the most advanced techniques and processes to its products. When combined with ongoing and intense research and engineering efforts directed to understanding the many complexities of contemporary valve trains and systems, the results stand on their own technological merits. Superiority is not claimed, it is earned.
Check out this video to see how the nitriding process happens. 
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