Graded Hard Carbon Piston Ring Coating Against Peeling and Wear
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Solution Overview
Problem
Amorphous hard carbon films used in piston rings face issues with adhesion to the base material, leading to peeling and wear due to residual stress and chemical stability, especially under high thermal conductivity and surface pressure conditions.
Innovation Solution
A graded structure in the amorphous hard carbon film with a continuously or stepwisely increasing sp2 bond ratio from the inner to the outer surface enhances adhesion and wear resistance, preventing peeling and chipping by balancing film strength and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an amorphous hard carbon film with high sp3 bond ratio is formed to achieve low friction coefficient, then wear resistance is improved, but adhesion to base material deteriorates due to large residual stress
Solution Approach 1:
The patent applies local quality by creating a graded structure where the sp3 bond ratio varies through the film thickness. The inner surface region has a lower sp3 bond ratio (higher adhesion) while the outer surface region has a higher sp3 bond ratio (lower friction), allowing each region to optimize its local function.
Solution Approach 2:
The patent changes the physical parameter of sp3 bond ratio continuously or stepwise from the inner surface to the outer surface of the film. This parameter gradient allows the film to transition from a state favorable for adhesion to a state favorable for low friction and wear resistance.
2Duration of action of stationary object
If film thickness is increased to improve wear resistance, then durability is improved, but peeling resistance deteriorates due to accumulated residual stress
Solution Approach 1:
The graded sp3 bond ratio structure creates local variations in stress distribution. The inner region with lower sp3 content acts as a stress-absorbing layer that prevents stress accumulation, allowing the outer thick region to provide wear protection without peeling.
Solution Approach 2:
The film functions as a composite structure with varying composition (sp2/sp3 ratio) through its thickness. This composite nature allows simultaneous achievement of adhesion (inner region), low friction (outer region), and stress management (graded transition zone).
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 graded structure effectively suppresses peeling and ensures high wear resistance of the amorphous hard carbon film on piston rings, even under severe conditions of high temperature and surface pressure, maintaining film integrity and functionality.
Implementation Method 1
the amorphous hard carbon film is formed by PVD
Data Source
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AI summary
The disclosure relates to a sliding member. This sliding member includes a base material and an amorphous hard carbon film formed on a surface of the base material and the amorphous hard carbon film has a graded structure in which a sp2 ratio increases from an inner surface side corresponding to the base material side toward an outer surface side. Further, the disclosure relates to a piston ring which includes the sliding member.