Piston Ring Coating That Hardens Under Engine Heat
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Solution Overview
Problem
Piston rings in internal combustion engines face wear issues due to gas and inherent loads, and existing coatings like hexavalent chromium pose environmental and health risks, while requiring heat treatment that exposes the material to excessive temperatures.
Innovation Solution
A coated piston ring with alternating layers of trivalent chromium and nickel-phosphorous, which forms a hard ternary compound layer when exposed to engine heat, providing wear resistance without heat treatment and eliminating hexavalent chromium exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hexavalent chromium coating is applied to enhance wear resistance, then wear resistance is improved, but environmental and health risks increase
Solution Approach 1:
The patent changes the chemical composition parameters of the coating from hexavalent chromium to trivalent chromium combined with nickel and phosphorous. This parameter change maintains wear resistance while eliminating the harmful effects associated with hexavalent chromium, directly resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent uses a composite coating structure with multiple layers containing different materials (trivalent chromium, nickel, phosphorous) that work together to achieve wear resistance. This composite approach replaces the single-material hexavalent chromium coating, providing the necessary protective properties without the environmental and health risks.
2Reliability
If heat treatment is applied to form hard coating layers, then wear resistance is improved, but excessive temperatures are exposed to the material
Solution Approach 1:
The coating structure is designed to automatically form the desired hard compound layers through exposure to normal engine operating temperatures. The trivalent chromium, nickel, and phosphorous layers self-organize to create protective compounds without requiring external heat treatment, thus achieving wear resistance without excessive temperature exposure.
Solution Approach 2:
The coating is pre-configured with specific layers (trivalent chromium, nickel, phosphorous) during manufacturing that are designed to react and form hard compounds at engine operating temperatures. This preliminary preparation eliminates the need for subsequent heat treatment, resolving the contradiction between achieving wear resistance and avoiding excessive heat exposure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a stable, low-wear piston ring with a hardness comparable to PVD coatings, reducing environmental and health risks associated with hexavalent chromium and avoiding excessive heat treatment temperatures.
Implementation Method 1
forms a hard ternary compound layer when exposed to engine heat
Implementation Method 2
forms a hard ternary compound layer when exposed to engine heat
Data Source
AI summary
A wear resistant coated piston ring for an engine is provided. The piston ring includes a coating disposed on a ring body. The coating includes initially includes alternating first and second layers, wherein the first layers include trivalent chromium, and the second layers include nickel and phosphorous. The first layers are applied by depositing a trivalent chromium electrolyte, specifically Cr3+ electrolyte. The second layers are applied by electroless deposition. The coating is left in the as-is condition and is not heat treated before being disposed on a piston and then in an engine. The coating is naturally exposed to heat while the engine is running, and this heat causes the chromium, nickel, and phosphorous of the layers to diffuse and form a surface layer on a compound layer. The surface layer includes trivalent chromium, and the compound layer includes a ternary compound of chromium, nickel, and phosphorous.