Copper Alloy Sliding Member With Ferrite-Rich Bonding Interface
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Solution Overview
Problem
Conventional sliding members for bearings in internal combustion engines and automatic transmissions experience shear at the interface between the copper alloy sliding layer and the steel back-metal layer due to differences in elastic deformation, leading to potential breakage under dynamic loads, despite improved bonding strength from techniques like using Cu—Sn—Fe-based alloys.
Innovation Solution
A sliding member with a back-metal layer composed of hypoeutectoid steel containing 0.07 to 0.35% carbon, featuring a high ferrite phase portion at the bonding surface with a reduced pearlite volume ratio, which minimizes elastic deformation differences with the copper alloy sliding layer, enhancing bonding strength and resistance to shear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sliding member with copper alloy sliding layer and steel back-metal layer is used, then seizure resistance and wear resistance are provided, but shear occurs at the interface between sliding layer and back-metal layer under dynamic load due to difference in elastic deformation
Solution Approach 1:
The back-metal layer is designed with non-uniform microstructure: a first region adjacent to the sliding layer contains predominantly ferrite phase with minimal pearlite, while a second region farther from the sliding layer contains pearlite. This local differentiation allows the ferrite-rich region to match the elastic deformation characteristics of the copper alloy sliding layer, preventing shear at the interface, while the pearlite-containing region provides overall strength to the back-metal layer.
Solution Approach 2:
The invention changes the microstructural parameters of the back-metal layer by controlling the distribution and volume ratios of ferrite and pearlite phases. Specifically, the ferrite phase volume ratio in the first region is set to 80-95% to minimize elastic deformation difference with the sliding layer, while the pearlite phase volume ratio in the second region is maintained at 20-60% to ensure sufficient strength. This parameter optimization resolves the contradiction between bonding strength and shear resistance.
2Weight of moving object
If weight reduction is achieved in internal combustion engine and automatic transmission, then fuel consumption is reduced, but bearing housing rigidity decreases leading to increased elastic deformation under dynamic load
Solution Approach 1:
The invention optimizes the microstructural parameters of the back-metal layer to accommodate the reduced rigidity of lightweight bearing housings. By creating a ferrite-rich region adjacent to the sliding layer, the back-metal layer's elastic deformation characteristics are tuned to match those of the copper alloy sliding layer. This allows the sliding member to function reliably even when subjected to the increased elastic deformation caused by lightweight, flexible bearing housings in modern fuel-efficient engines and transmissions.
3Strength
If the back-metal layer is made stronger to prevent shear, then bonding strength improves, but the difference in elastic deformation with copper alloy sliding layer increases causing shear at interface
Solution Approach 1:
The back-metal layer is designed with spatially varying microstructure: the first region adjacent to the sliding layer is enriched with ferrite phase (80-95% volume ratio) to match elastic deformation characteristics and ensure strong bonding, while the second region contains pearlite phase (20-60% volume ratio) to provide overall strength. This local quality differentiation resolves the contradiction by allowing the back-metal layer to be strong where needed while being compliant at the interface.
Solution Approach 2:
The back-metal layer functions as a composite material system with two distinct microstructural regions having different mechanical properties. The ferrite-rich first region provides elastic compliance matching the copper alloy sliding layer, while the pearlite-containing second region contributes strength. This composite approach allows simultaneous achievement of strong bonding and high strength in the back-metal layer.
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 high ferrite phase portion at the bonding surface reduces the likelihood of shear between the copper alloy and the back-metal layer, ensuring strong bonding and maintaining structural integrity under dynamic loads, while the pearlite-rich center portion maintains necessary strength for the back-metal layer.
Implementation Method 1
since there is a difference in amount of elastic deformation between the sliding layer including the copper alloy and the steel back-metal layer, shear occurs in some cases at an interface between the sliding layer and the steel back-metal layer
Implementation Method 2
The back-metal layer includes a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon and has a structure including a ferrite phase and pearlite
Data Source
AI summary
Provided is a sliding member including: a back-metal layer and a sliding layer including a copper alloy. The back-metal layer includes a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon and has a structure including a ferrite phase and pearlite. The back-metal layer has a high ferrite phase portion at a bonding surface between the back-metal layer and the sliding layer. A volume ratio Pc and a volume ratio Ps satisfy Ps/Pc≤0.4, where the volume ratio Pc is a volume ratio of pearlite in the structure at a center portion in a thickness direction of the back-metal layer, and the volume ratio Ps is a volume ratio of pearlite in the high ferrite phase portion.