Surface treatment / Fine particle peening
WPC treatment (fine particle peening)
WPC treatment is a type of fine particle peening that modifies metal surfaces by blasting them at high speed with particles of about 200 μm or smaller. It creates compressive residual stress and micro-dimples on the surface, improving fatigue strength, wear resistance and sliding properties.
How it works
"Why it works"WPC treatment is a form of shot peening that propels particles smaller than those of conventional shot peening onto a metal surface at high speed. The plastic deformation caused by the impacts leaves compressive residual stress near the surface.
The impacts also form countless micro-dimples on the surface. These dimples act as oil reservoirs that retain lubricant, preventing oil-film breakdown and reducing friction on sliding surfaces.
Under some conditions the surface grain structure is refined and hardness increases. Unlike plating or painting, the treatment adds no separate layer: it modifies the material surface itself.
Main effects
- Higher fatigue strength (compressive residual stress suppresses the initiation and growth of fatigue cracks)
- Better sliding properties and lower friction (oil-reservoir effect of the micro-dimples)
- Higher wear and seizure resistance
- Higher surface hardness
- Better adhesion of DLC and other coatings when used as a pre-treatment
Definitions
- WPC treatmentRegistered trademark
- A surface modification process that blasts fine particles onto metal at high speed to create compressive residual stress and micro-dimples. Classified as fine particle peening.
- Fine particle peening
- Shot peening with media of about 200 μm or smaller. The affected layer is shallower than in conventional shot peening, but it is well suited to modifying the near-surface region and forming fine surface texture.
- Compressive residual stress
- Stress that remains in a material after external loads are removed and acts to compress it. At the surface, it suppresses fatigue cracks that start from tensile stress.
- Micro-dimple
- A micrometre-scale depression distributed across a surface. Micro-dimples retain lubricant and reduce the contact area with mating parts or products.
Applications
"Where it is used"| Field | Examples |
|---|---|
| Automotive and motorsports | Gears, camshafts, pistons and other engine and drivetrain parts |
| Machine elements | Springs, bearing components, sliding parts |
| Molds and dies | Treating forming surfaces for better release and durability |
| Blades and cutting tools | Longer edge life |
Typical process conditions
"Under what conditions"These are general guides. Actual conditions are set by the supplier for each part, material and specification.
| Item | Typical |
|---|---|
| Media | Fine particles of about 200 μm or smaller (metal, ceramic, etc.) |
| Materials | Steel, stainless steel, aluminum alloys, titanium alloys and other metals |
| Affected depth | Several tens of μm from the surface |
| Dimensional change | Very small (micrometre order) |
| Surface finish | Satin finish from fine dimples |
| Combined treatments | With DLC coating or lapping |
FAQ
"Direct answers"What is the difference between WPC treatment and shot peening?
WPC treatment is a type of shot peening that uses smaller particles at high speed. The affected layer is shallower, but it excels at modifying the near-surface region and forming fine dimples, which suits precision and sliding parts.
Can WPC treatment be combined with DLC coating?
Yes. Applying WPC treatment as a pre-treatment improves the adhesion of the DLC film, and some suppliers offer this combined treatment.
Does WPC treatment change part dimensions?
Only very slightly, on the micrometre order. For tight-tolerance parts, share the drawing and required accuracy with the supplier in advance.
Can I order a single piece?
It depends on the supplier. See the minimum lot column in the comparison table below for each company's published information.
Which companies in Japan offer WPC treatment?
Among the companies listed on FactoryMatch, Fuji WPC Co., Ltd. offer WPC treatment (based on each company's published information). See the supplier comparison table for minimum lots and overseas support.
Suppliers
"Who to ask"WPC treatment and Fuji WPC Co., Ltd.
“WPC処理” (WPC treatment) is Japanese trademark registration No. 3081805, held jointly by three companies: Fuji Kihan Co., Ltd., Fuji Manufacturing Co., Ltd. and Fuji WPC Co., Ltd. The technology was jointly developed by Fuji Manufacturing (不二製作所) and Fuji Kihan (不二機販). Fuji WPC Co., Ltd. (Sagamihara, Kanagawa) was established in April 1997 as a contract processing base in the Kanto region, jointly funded by these two companies to promote WPC Treatment® and develop its applications. Because information about several companies with “Fuji” in their names is often mixed up in English-language searches, the relationship is set out here.
Based on the listed companies' published information.
| Company | Location | Relevant technology | Minimum lot | Overseas support |
|---|---|---|---|---|
| Fuji WPC Co., Ltd. | Sagamihara, Kanagawa | WPC Treatment® | From 1 pc | English inquiry OK, 2005: established the US subsidiary WPC Treatment Co., Inc in Los Angeles |