Sliding Member with Graded Hard Coating for Piston Rings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional techniques fail to achieve both excellent wear resistance and high coating adhesion for sliding members under severe sliding conditions without subjecting the base member to nitriding treatment, as nitriding lowers thermal conductivity and conventional hard coatings suffer from adhesion issues with lubrication oil debris.
Innovation Solution
A sliding member with a steel base material having a thermal conductivity of at least 30 W/m-K, featuring a hard coating with a specific Young's modulus distribution from the interface to the surface, comprising multiple layers of amorphous hard carbon with varying Young's modulus to enhance adhesion and wear resistance, without nitriding the base member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If nitriding treatment is applied to the base member, then wear resistance is improved, but thermal conductivity is lowered
Solution Approach 1:
The patent divides the protective structure into two separate components: the base member made of steel material with high thermal conductivity (30 W/m·K or higher) and a hard coating layer applied on its surface. This segmentation allows the base member to maintain thermal conductivity while the coating layer provides wear resistance, eliminating the need for nitriding treatment that would compromise thermal properties.
Solution Approach 2:
The patent employs a composite structure combining a steel base material with specific physical properties (high thermal conductivity) and a hard coating layer with superior wear resistance. This composite approach allows each layer to fulfill its specific function optimally, resolving the contradiction between thermal conductivity and wear resistance.
2Reliability
If conventional hard coating is applied to maintain thermal conductivity, then thermal conductivity is preserved, but coating adhesion deteriorates under severe sliding conditions
Solution Approach 1:
The patent applies local quality by creating a hard coating layer with specific properties (hardness, thickness, composition) only on the surface region where wear resistance is needed, while the base member maintains its high thermal conductivity throughout. The coating layer's local characteristics are optimized for adhesion and wear resistance without compromising the base material's thermal properties.
3Strength
If hard coating is applied to achieve wear resistance, then wear resistance is improved, but coating peeling occurs due to plastic deformation of the base member
Solution Approach 1:
The patent changes the parameters of the coating layer including its hardness (20 GPa to 45 GPa), thickness (1 μm to 5 μm), and composition to create an optimal balance between wear resistance and adhesion. By carefully controlling these parameters, the coating provides sufficient hardness for wear protection while maintaining flexibility and adhesion to prevent peeling under sliding conditions.
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 achieves excellent wear resistance and high coating adhesion under severe sliding conditions, maintaining the base member's thermal conductivity and preventing coating peeling, as demonstrated by the reciprocating sliding test results.
Implementation Method 1
the hard coating has a Young's modulus having a distribution to increase first in a depth direction directed from an interface between the hard coating and the base member to a surface, to become maximum at a predetermined depth, and then to decrease in the depth direction directed from the interface to the surface
Implementation Method 2
the base member made of a steel material having a high thermal conductivity of at least 30 W/m·K... In order to effectively dissipate heat in a combustion chamber from a piston to a cylinder wall surface via the piston ring, the piston ring needs to have high thermal conductivity
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Provided is a sliding member capable of achieving excellent wear resistance and high coating adhesion under harsh sliding conditions without subjecting a base member to nitriding treatment. The sliding member includes a base member made of a steel material and a hard coating that is formed on the base member and having a surface serving at least as a sliding surface. The hard coating has a Young's modulus having a distribution to increase first in a depth direction directed from an interface between the hard coating and the base member to the surface, to become maximum at a predetermined depth, and then to decrease in the depth direction directed from the interface to the surface.