Gray Cast Iron Brake Disk Surface Layers for Uniform Nitriding
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Solution Overview
Problem
Gray cast iron brake disks suffer from low erosion resistance, rust formation, and thermal fatigue, leading to reduced durability and quality issues due to the difficulty in diffusing nitrogen into the material, resulting in a thin and non-uniform nitride compound layer.
Innovation Solution
A brake disk with a decarburized layer and a nitride compound layer formed on gray cast iron, where the decarburization process is followed by nitriding to enhance erosion resistance and wear resistance, with specific thickness ratios and heat treatment conditions to prevent crack generation and improve durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional nitriding is performed directly on gray cast iron, then nitrogen diffusion is attempted, but the nitride compound layer formed is thin and non-uniform due to difficulty in nitrogen diffusion
Solution Approach 1:
The patent applies preliminary decarburization treatment before nitriding to prepare the gray cast iron surface. This preliminary action removes carbon from the surface layer, creating a decarburized layer that facilitates subsequent nitrogen diffusion. By performing this preparatory step, the surface structure is optimized for nitrogen uptake, enabling formation of a thicker and more uniform nitride compound layer without requiring excessively long nitriding times.
Solution Approach 2:
The patent changes the chemical composition parameters of the surface layer through controlled decarburization. By reducing carbon content in the surface layer while maintaining the base gray cast iron composition, the surface becomes more receptive to nitrogen diffusion. This parameter change in carbon concentration creates optimal conditions for subsequent nitriding, resolving the contradiction between layer thickness and uniformity.
2Reliability
If heat treatment time is extended to form a thicker nitride compound layer, then erosion resistance improves, but processing time increases
Solution Approach 1:
The decarburization step serves as a preliminary action that pre-prepares the surface structure to enhance nitrogen diffusion rate. By creating the decarburized layer beforehand, the subsequent nitriding process achieves thicker nitride compound layer formation in reduced time, thereby improving erosion resistance without proportionally increasing processing time.
Solution Approach 2:
The patent changes the surface carbon content parameter through decarburization, which fundamentally alters the diffusion kinetics during nitriding. This parameter change enables faster nitrogen penetration and thicker nitride layer formation in shorter time, resolving the time-resistance contradiction.
3Reliability
If decarburized layer thickness is increased to improve erosion resistance, then surface quality improves, but the ratio of decarburized layer to nitride compound layer changes
Solution Approach 1:
The patent optimizes the decarburization parameters (time, temperature, atmosphere) to achieve a specific decarburized layer thickness that balances erosion resistance with appropriate thickness ratio. By controlling the decarburization degree parameter, both the absolute thickness for erosion resistance and the relative ratio for structural integrity are simultaneously optimized.
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 achieves enhanced erosion resistance, reduced crack generation due to thermal fatigue, and improved wear resistance, while reducing processing time through a short heat treatment process, resulting in a more durable brake disk with improved surface quality.
Implementation Method 1
a decarburized layer formed on the basic material and formed via decarburizing
Implementation Method 2
a nitride compound layer formed on the decarburized layer and formed of nitride via nitriding
Implementation Method 3
performing heat treatment on one surface of the basic material to form a pre-decarburized layer
Data Source
AI summary
A brake disk includes a basic material formed of gray cast iron, a decarburized layer formed on the basic material and formed via decarburizing, and a nitride compound layer formed on the decarburized layer and formed via nitriding of a nitride. A method of manufacturing a brake disk includes preparing a disk formed of gray cast iron, performing heat treatment of the disk to form a pre-decarburized layer and a base layer of gray cast iron over which the pre-decarburized layer is formed, and nitriding a portion of the pre-decarburized layer to form a nitride compound layer including a nitride and a decarburized layer over which the nitride compound layer is formed.