Brake Disk Composite Wear Layer for Crack-Resistant Friction Brakes
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Solution Overview
Problem
Friction brakes in motor vehicles experience significant wear and corrosion due to the frictional contact between the brake disk and pad, leading to abrasion and brake dust generation, which existing antiwear layers fail to adequately address.
Innovation Solution
A friction brake element with an antiwear layer made of ferritic-austenitic steel containing finely dispersed hard material particles, such as carbides, oxides, or borides, and an optional intermediate layer of pure ferritic-austenitic steel, applied via laser buildup welding or thermal spraying, providing enhanced wear, corrosion, and cracking resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an antiwear layer is applied to the brake disk, then wear resistance is improved, but the layer may be prone to cracking under thermomechanical stresses
Solution Approach 1:
The antiwear layer is designed as a composite material consisting of a ferritic-austenitic steel matrix with embedded hard particles (such as carbides, oxides, nitrides, or borides). The ferritic-austenitic steel provides a two-phase microstructure where austenite islands within the ferritic matrix enhance crack resistance by stopping crack propagation at phase boundaries, while the hard particles dispersed throughout the matrix provide wear resistance. This composite structure resolves the contradiction between wear resistance and crack resistance.
2Reliability
If hard material particles are added to increase wear resistance, then abrasion resistance is improved, but the coefficient of thermal expansion mismatch between layer and main element increases causing stresses and potential cracking
Solution Approach 1:
The patent carefully controls the proportion of hard material particles to be less than or equal to 70% by volume of the antiwear layer, and ensures a matrix phase proportion of at least 30% by volume. This parameter optimization balances wear resistance (provided by hard particles) with stress resistance (provided by the ductile ferritic-austenitic steel matrix), preventing excessive thermal expansion mismatch and cracking while maintaining high abrasion resistance.
3Reliability
If chromium and nitrogen are added to increase corrosion resistance, then corrosion protection is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies compositional parameters for the ferritic-austenitic steel matrix, including the addition of chromium and/or nitrogen to enhance corrosion resistance. By defining specific compositional ranges and utilizing standard metallurgical processes for producing ferritic-austenitic steels, the patent achieves improved corrosion resistance while maintaining manufacturability through established industrial practices.
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 significantly reduces abrasion, corrosion, and cracking of the brake disk, ensuring low wear rates and preventing crack propagation, thereby increasing the durability and reliability of the friction brake element.
Implementation Method 1
At the phase boundaries, in particular at the transition from ferrite to the more ductile austenite, cracks that arise during cooling or under the thermomechanical stresses during braking operations come to a stop for fracture-mechanical reasons
Implementation Method 2
The antiwear layer is applied to the main element by laser buildup welding or thermal spraying
Implementation Method 3
The antiwear layer is applied to the main element by laser buildup welding or thermal spraying
Data Source
AI summary
A friction brake body for a friction brake of a motor vehicle, in particular a brake disk, includes a base body made in particular from gray cast iron and having at least one wear resistant layer formed on a friction contact surface of the base body. The wear resistant layer is made from ferritic-austenitic steel and includes an incorporated hard material particle, in particular finely distributed hard material particle.