Double-Layer Brake Disc Coating for Wear and Nickel Release
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Solution Overview
Problem
Traditional brake discs made of gray cast iron or steel suffer from excessive wear and surface oxidation, leading to rust formation, and existing protective coatings often flake off, releasing nickel particles which can cause sensitization and are essential for strength and corrosion resistance, making it difficult to maintain performance and reduce nickel release simultaneously.
Innovation Solution
A brake disc with a base layer of steel containing reduced or no nickel, combined with a protective surface coating of carbides such as tungsten carbide, chromium carbide, or niobium carbide, deposited using high-velocity techniques, to enhance wear resistance and mechanical strength while minimizing nickel particle release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional protective coatings containing nickel are applied to brake discs, then wear resistance and corrosion resistance are improved, but nickel particles are released causing sensitization and health concerns
Solution Approach 1:
The protective coating is segmented into multiple layers: a base layer containing nickel for corrosion resistance and wear resistance, and a top layer free of nickel and free carbon to prevent particle release and sensitization. This segmentation allows each layer to perform its specific function while eliminating the harmful effects of nickel exposure.
Solution Approach 2:
Different regions of the coating have different compositions tailored to their specific functions. The base layer has high nickel content for maximum protection, while the top layer has zero nickel content to eliminate sensitization risks. This local differentiation of material properties resolves the contradiction between needing nickel for protection and avoiding nickel for health safety.
2Object-generated harmful factors
If nickel is removed from the steel base layer, then nickel particle release is reduced, but mechanical strength and toughness deteriorate
Solution Approach 1:
The brake disc structure is segmented into a nickel-containing base layer for mechanical strength and a nickel-free top layer for health safety. This segmentation allows the nickel to remain in the structure where it provides strength without being exposed to the environment where it would cause sensitization.
Solution Approach 2:
The nickel-free top layer acts as an intermediary barrier between the nickel-containing base layer and the external environment. It protects the nickel in the base layer from oxidizing and releasing particles, while allowing the nickel to maintain its structural function without causing sensitization.
3Ease of manufacture
If free carbon is present in the protective coating, then coating formation is simplified, but coating detachment and flaking occur
Solution Approach 1:
The chemical composition parameters of the coating are changed by eliminating free carbon from the top layer while maintaining nickel content at zero. This parameter change prevents the formation of free carbon compounds that would cause detachment, while still allowing for effective coating formation through controlled deposition processes.
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 effectively reduces nickel particle release, maintains thermal and mechanical performance, and decreases resource consumption, providing a durable and reliable brake disc with improved wear resistance and reduced environmental impact.
Implementation Method 1
The deposition of the material in particle form is obtained by the HVOF (High Velocity Oxygen Fuel) technique
Implementation Method 2
by the HVAF (High Velocity Air Fuel) technique
Implementation Method 3
by the KM (Kinetic Metallization) technique
Implementation Method 4
depositing a material in particle form composed of 70 to 95% by weight of tungsten carbide, 5% to 15% by weight of cobalt and 1% to 10% by weight of chromium
Data Source
AI summary
A brake disc for disc brake comprises a braking band made of gray cast iron or steel, provided with two opposite braking surfaces, each of which defines at least partially one of the two main faces of the disc. The brake disc is provided with a base layer totally nickel-free and one or more carbides included in the nickel-free steel, which covers at least one of the two braking surfaces of the braking band. An intermediate layer composed of nickel-free steel is interposed between the base layer and at least one of the two braking surfaces of the braking band.