CoP-Coated Brake Disc for Corrosion Resistance and Post-Machining
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Solution Overview
Problem
Existing brake discs face issues with corrosion and wear resistance, particularly in wet climates and regions where salt is used to control road conditions, leading to premature wear and environmental concerns due to brake dust.
Innovation Solution
A corrosion and wear-resistant brake disc is developed with a precipitation-hardened cobalt-phosphorus (CoP) alloy coating electrodeposited on the braking surface, which exhibits excellent bond strength and allows for post-deposition machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If post-coating machining is performed on conventional hard and brittle protective coatings, then dimensional tolerances can be achieved, but the process is costly, time-consuming, and may cause damage to the coating such as chipping or cracking
Solution Approach 1:
The invention changes the mechanical property parameters of the coating, specifically its hardness and brittleness, by controlling the composition (chromium ≥10%, carbon ≥20%) and the deposition process parameters. This results in a coating that is sufficiently soft during machining to avoid damage, yet achieves the required hardness for wear resistance after machining
Solution Approach 2:
The invention performs the machining operation while the coating is in a softer, more ductile state before final hardening. This preliminary machining action allows for easier material removal without damaging the coating, and the coating is subsequently hardened to achieve the required wear resistance
2Weight of moving object
If aluminum discs are used to reduce weight, then the weight of the brake disc is reduced, but the aluminum base is vulnerable to temperatures generated during braking that are above its softening point
Solution Approach 1:
The invention applies a protective coating with specific local properties (high chromium and carbon content) on the surface of the aluminum disc, creating a gradient structure where the lightweight aluminum core provides low weight while the chromium-rich surface layer provides high-temperature resistance and protection. This local quality differentiation resolves the contradiction between weight reduction and temperature resistance
3Reliability
If titanium, carbon, or carbon-ceramic materials are used to improve braking performance, reduce weight, and reduce wear, then performance is significantly improved, but the cost increases substantially
Solution Approach 1:
The invention creates a cost-effective composite coating system that combines chromium and carbon in specific proportions to achieve performance properties similar to expensive titanium or carbon-ceramic materials. The composite nature of the coating provides wear resistance, temperature resistance, and corrosion resistance at a fraction of the cost of alternative materials
Solution Approach 2:
The invention uses a relatively inexpensive coating material composition (chromium and carbon-based) that can be applied to extend the service life of the brake disc, providing a cost-effective alternative to expensive long-lasting materials like carbon-ceramic. The coating acts as a protective layer that significantly extends the life of the underlying disc material
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 CoP alloy coating provides superior resistance to wear and corrosion, maintains structural integrity, and allows for post-coating machining, addressing the limitations of conventional coatings and improving the performance and durability of brake discs.
Implementation Method 1
a wear-resistant coating electrodeposited on the braking surface
Implementation Method 2
heat treating the coated disc body to precipitation harden the CoP alloy
Data Source
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AI summary
A corrosion and wear-resistant brake disc is disclosed. The brake disc comprises a brake body having at least one braking surface, and a corrosion and wear-resistant coating electrodeposited on the braking surface. The corrosion and wear-resistant coating comprises a precipitation-hardened cobalt-phosphorus (CoP) alloy and exhibits a Vickers hardness of from about 900 to about 1050 HV. A method of preparing the brake disc is also disclosed, and comprises electrodepositing a cobalt-phosphorus (CoP) alloy onto at least one braking surface of a disc body to a thickness of at least about 150 µm to give a coated disc body. The method also comprises heat treating the coated disc body to precipitation harden the CoP alloy and give the corrosion and wear-resistant coating on the braking surface.