Friction Material Coating Layer Structure for Corrosion Resistance
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Solution Overview
Problem
Conventional friction materials bonded to a steel back plate via copper plating suffer from inferior corrosion resistance due to pinholes, leading to rust and reduced bonding strength, and thick copper plating can cause dimensional variations and increased costs.
Innovation Solution
A friction material with a specific coating layer structure, comprising a first layer of Cu, Ni, and Fe alloy and a second layer of Cu and Ni alloy, with controlled thickness and composition, to prevent pinholes and enhance adhesion and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper plating of not less than 30 μm in coating thickness is used to fill pinholes and improve corrosion resistance, then corrosion resistance is improved, but coating thickness variation increases, plating time becomes longer, and costs increase
Solution Approach 1:
The coating layer is divided into multiple distinct layers (first coating layer, second coating layer, and optionally third coating layer) with different compositions and functions. The first layer provides corrosion resistance with 1-45 atom% Cu, 1-45 atom% Ni, and 10-95 atom% Fe, while the second layer provides adhesion with 5-60 atom% Cu and 40-95 atom% Ni, eliminating the need for excessive thickness to achieve both protection and uniformity
Solution Approach 2:
Each coating layer is designed with specific local composition and thickness characteristics tailored to its function. The first coating layer has higher Fe content for corrosion resistance, the second layer has higher Ni content for adhesion, and their thicknesses are optimized locally (first layer: 1-6 μm, second layer: 9.5-24 μm) rather than using uniform thick coating throughout
Solution Approach 3:
The coating structure uses composite material design with multiple layers of different alloy compositions. The combination of Cu-Ni-Fe alloy in the first layer and Cu-Ni alloy in the second layer creates a composite structure that achieves superior corrosion resistance and adhesion with controlled total thickness, avoiding the dimensional variations and costs associated with single-layer thick copper plating
2Reliability
If copper plating of not less than 30 μm in coating thickness is used to fill pinholes, then corrosion resistance is improved, but plating time becomes longer, leading to increase in costs
Solution Approach 1:
The coating is segmented into functional layers with the first coating layer (1-6 μm) providing corrosion resistance and the second coating layer (9.5-24 μm) providing adhesion. This segmentation allows achieving adequate corrosion protection with reduced total thickness compared to uniform 30 μm copper plating, thereby reducing plating time
Solution Approach 2:
The invention changes the compositional parameters of the coating layers, using Cu-Ni-Fe alloy in the first layer and Cu-Ni alloy in the second layer with optimized thicknesses. This parameter optimization enables achieving the required corrosion resistance with shorter plating time than conventional thick copper plating
3Reliability
If excessively thick layer of plating is used to fill pinholes, then corrosion resistance is improved, but peeling of plating occurs
Solution Approach 1:
The coating is segmented into functionally distinct layers where the first coating layer (1-6 μm) with Cu-Ni-Fe alloy provides corrosion resistance, and the second coating layer (9.5-24 μm) with Cu-Ni alloy provides adhesion. This segmentation prevents peeling by ensuring the adhesion layer has optimal thickness and composition, while the corrosion protection layer has sufficient but not excessive thickness
Solution Approach 2:
Each layer has locally optimized composition and thickness: the first layer has 1-45 atom% Cu, 1-45 atom% Ni, and 10-95 atom% Fe with thickness of 1-6 μm for corrosion resistance, while the second layer has 5-60 atom% Cu and 40-95 atom% Ni with thickness of 9.5-24 μm for adhesion. This local optimization prevents peeling while maintaining adequate corrosion protection
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 friction material exhibits superior corrosion resistance and adhesion, reducing rust generation and peeling, while maintaining dimensional accuracy and reducing plating time and costs.
Implementation Method 1
conventional friction material that is made by sintering-bonding a friction part to a back plate (for example, a steel material) via copper plating
Data Source
AI summary
A friction material comprising a Fe part; a coating layer formed over a surface of the Fe part; and a friction part formed on a surface of at least a part of the coating layer wherein: the coating layer comprises a first coating layer and a second coating layer in order from Fe part side, the first coating layer is constituted of an alloy containing Cu, Ni and Fe such that Fe content be not less than 10 atom %, the second coating layer is constituted of an alloy containing Cu and Ni, or an alloy containing Cu, Ni and Fe such that Fe content be less than 10 atom %, an average thickness of the first coating layer is not less than 1.0 μm and not more than 6.0 μm; and an average thickness of the second coating layer is not less than 9.5 μm and not more than 24.0 μm.