Brake Disc Coating Sequence for Corrosion Resistance and Adhesion
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Solution Overview
Problem
Current methods for improving wear and corrosion resistance of brake discs, such as thermal spraying and gas nitrocarburizing, do not meet the stricter requirements for longer-lasting components with enhanced resistance.
Innovation Solution
A corrosion-resistant coating system is created on a cast iron brake disc through surface activation with a pulsed water jet to increase surface roughness, followed by nitrocarburization to form a diffusion layer, and then oxidation to enhance corrosion resistance, with a thermally sprayed top layer applied to provide wear resistance and bridge surface cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thermally sprayed top layer is applied directly on a machined cast iron surface, then the wear resistance is improved, but the adhesion of the coating is insufficient due to smooth surface
Solution Approach 1:
The cast iron substrate undergoes pulsed water jet treatment before thermal spraying to create surface roughness and micro-cavities. This preliminary surface activation provides mechanical interlocking anchors for the subsequent thermally sprayed coating, ensuring strong adhesion while maintaining wear resistance.
2Ease of operation
If the top layer is applied thin to maintain braking properties, then the braking performance is preserved, but the coating cannot cover the surface roughness and cavities effectively
Solution Approach 1:
The pulsed water jet creates localized micro-cavities and undercuts at specific surface locations rather than uniform roughness. These localized features provide targeted adhesion points for the thermal spray coating, allowing thin coating application that maintains braking surface quality while ensuring adequate coverage and adhesion.
3Reliability
If the surface is highly roughened to improve coating adhesion, then the bonding is improved, but the braking properties deteriorate due to excessive surface roughness
Solution Approach 1:
The pulsed water jet process parameters (pressure, pulse duration, frequency) are optimized to create surface roughness within a specific range that provides adequate coating adhesion without exceeding the threshold that would deteriorate braking properties. This precise parameter control achieves the optimal balance between coating bonding and braking performance.
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 method significantly improves the adhesion and corrosion resistance of the coating system, making it more resistant to local damage and maintaining braking performance by forming a strong, durable diffusion layer and continuous oxide coating.
Implementation Method 1
the cast iron substrate is first subjected to activation by means of a pulsed water jet after completion of machining... the surface roughness of the surface thus treated is increased
Implementation Method 2
Hereinafter the surface is nitrocarburized so that a corresponding diffusion layer is formed on it
Implementation Method 3
Thereupon the surface is subjected to an oxidation process in a next step, which means that the surface or a part of the diffusion layer is oxidised
Implementation Method 4
the top layer is applied by thermal spraying
Data Source
AI summary
The invention relates to a method of producing a corrosion resistant coating system on a cast iron substrate preferably in the shape of a brake disc, the coating system being completed by a thermally sprayed top layer, characterised in that the cast iron substrate is first subjected to activation by means of a pulsed water jet after completion of machining which increases the surface roughness of the surface thus treated, whereupon the surface is nitrocarburized so that a corresponding diffusion layer is formed on it, whereupon the surface is subjected to an oxidation process in a next step and only then the top layer is applied by thermal spraying.