The WPC process was first developed to aid vehicles campaigning the 24 Hours of Le Mans race more than 10 years ago. Since its initial debut, the name WPC has drawn attention within the motorsports worlds of F1, Cart, and other open wheel racing series around the globe. WPC is not just limited to use in circuit racing though, it has also found a strong backing within the NHRA drag racing series and with top competitors in WRC.
What is WPC?
Simply stated, WPC is not a coating. Rather it is a metal surface treatment that enhances the surface to reduce friction and strengthen engine parts. WPC achieves this groundbreaking process by firing ultra-fine particles at the part's surface at very high speeds. The ultra-fine media of the WPC process, when projected at high velocity towards the product surface, creates compressive stress (the compressive load per unit area of an original cross section) at the impact points. At the same time, a micro-thermal reaction takes place. It effectively seals minor surface fractures, allowing a condensed surface to form improving surface density due to the compaction. This altered and highly compact surface condition overcomes the problem of brittleness that is usually encountered when metals are hardened. Treatable metals include steel, aluminum, titanium, copper, and brass as well as soft surfaced bearings. WPC can basically treat any metallic item in an unassembled state, from rotary apex seals to rear differentials.
The Micro-Dimple Advantage
Take a close look at the image at the top of page 57. Notice the fine striation lines on the metal? The fine grooves are engraved into the product surface at the time of factory machining. These striations are systematically transformed into micro-dimple indentations by the impact of the ultra-fine media during the WPC process. Following the post-WPC process, these non-directional dimples act as oil reservoirs, reducing surface contact between the peaks of the dimples and the opposing material. Thus, oil that would normally drain away, through the grooves in an untreated piece. However, when pressure is applied, the oil instead is retained in the dimples of a treated part. This helps to keep the surface fully lubricated. The unique micro-dimple formation pattern strengthens the surface by changing the ionic structure, creating a harder more durable product with less friction.
Traditional Shot-Peening vs. the WPC Process
The difference between shot-peening and the WPC treatment is rather astounding when exposed to the knowledge of how both are conducted. Shot peening is typically performed by blasting the surface with smaller median such as glass at higher speeds while hard shot peening is known to use round metal bb. Using a striking or hitting process, shot-peening compacts the metal on the surface but leaves the structure in a brittle state with little or no change in compressive stress.
The WPC process uses a special ceramic bead composition ranging from 20 microns or larger depending on the application and area being treated, which shot-peening can never duplicate. In comparison to shot-peening, the media being used for the WPC process is 50 times smaller and is applied at a higher velocity, pressure, and impact creating a higher compressive stress level. The numerous impacts during the WPC process not only increases the residual compressive stress but also causes it to reside a lot closer to the surface. "The result is a product that has durability unrivaled by conventional peening," states WPC Technical Director Ross Clarke.
Coating vs. WPC Treatment
"The main benefits of using the WPC process over coating techniques is simply nothing is being applied to the metal," states WPC President Izumi Ogawa. This lack of spray-on coatings enables the WPC process to be a permanent surface treatment, eliminating build-up or non-uniform coverage of the metal that is being treated. WPC acts to strengthen the metal itself as opposed to a coating, which is a hard-coating structure; yet, the core element under the spray-on material is exactly the same. Consider the coating process as a short term fix for your engine, as once the coating fails the metal below will once again fail at the same rate as before. "For WPC, since we don't apply anything to the surface there is actually nothing to come off, and bearing or rod journal diameters remain almost identical prior to treatment," states Ogawa.