US 12,442,100 B2
Piston ring with hard chromium layer and improved running-in behaviour
Peter Schmidt, Burscheid (DE); Sabine Balke, Burscheid (DE); and Stefan Lueer, Langenfeld (DE)
Assigned to Federal-Mogul Burscheid GmbH, Burscheid (DE)
Appl. No. 17/904,831
Filed by Federal-Mogul Burscheid GmbH, Burscheid (DE)
PCT Filed Feb. 17, 2021, PCT No. PCT/EP2021/053826
§ 371(c)(1), (2) Date Aug. 23, 2022,
PCT Pub. No. WO2021/170460, PCT Pub. Date Sep. 2, 2021.
Claims priority of application No. 10 2020 105 003.8 (DE), filed on Feb. 26, 2020.
Prior Publication US 2023/0147997 A1, May 11, 2023
Int. Cl. C25D 7/04 (2006.01); C25D 3/04 (2006.01); C25D 5/00 (2006.01); C25D 5/12 (2006.01); C25D 5/48 (2006.01); F16J 9/26 (2006.01)
CPC C25D 7/04 (2013.01) [C25D 3/04 (2013.01); C25D 5/12 (2013.01); C25D 5/48 (2013.01); C25D 5/625 (2020.08); F16J 9/26 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A piston ring, comprising:
a base body having an inner circumferential surface, a first flank surface, a second flank surface and an outer circumferential surface,
a first chromium layer with a crack network applied to the outer circumferential surface,
wherein the crack network of the first chromium layer has a crack density of 10-250 cracks per mm and solid particles having an average particle size of 0.01-10 μm are embedded in the cracks of the first chromium layer,
a second chromium layer having a crack network applied on the first chromium layer,
the crack density of the crack network of the second chromium layer being 10-250 cracks per mm, wherein no solid particles are embedded in the cracks of the second chromium layer, the cracks on the surface of the second chromium layer have an average width of 1-15 μm, the cracks on the surface of the second chromium layer are electrolytically expanded and the surface proportion of the cracks on the surface of the second chromium layer is 3-25%, based on a total surface of the second chromium layer.