Cylinder Drum Wear-Resistant Layer Nitrocarburizing
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Solution Overview
Problem
Hydrostatic axial piston machines face challenges in achieving durable and resistant wear-resistant layers, particularly under high system pressures and frictional forces, which affect the service life and reliability of the machines.
Innovation Solution
A cylinder drum with a wear-resistant layer produced by nitrocarburizing in a salt bath or gas, resulting in a thin ductile connecting layer of 4 to 16 μm thickness, combined with a thick diffusion layer of at least 50 μm, enhancing Hertzian stress resistance and process reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional nitriding or nitrocarburizing methods are used to produce a wear-resistant layer, then the layer provides good abrasive and adhesive wear resistance, but the connecting layer becomes too thick leading to excessive Hertzian stress and reduced reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the connecting layer (4-16 μm) and diffusion layer (≥50 μm) through optimized nitrocarburizing parameters including temperature (500-550°C), time (2-8 hours), and medium composition (salt bath or gas). This resolves the contradiction by achieving sufficient wear resistance while maintaining Hertzian stress resistance through controlled layer thickness.
2Strength
If the connecting layer is made thinner to improve Hertzian stress resistance, then the wear resistance may be compromised, but the patent achieves both thin connecting layer and high wear resistance
Solution Approach 1:
The patent creates a composite structure with three distinct layers: oxide layer (0.5-5 μm), connecting layer (4-16 μm), and diffusion layer (≥50 μm). Each layer serves a specific function - the connecting layer provides Hertzian stress resistance while the thick diffusion layer ensures wear resistance. This composite approach resolves the contradiction between thin connecting layer and high wear resistance.
Solution Approach 2:
The patent applies local quality by creating different layer thicknesses and properties at different depths. The surface oxide layer provides initial protection, the thin connecting layer (4-16 μm) minimizes stress concentration, while the thick diffusion layer (≥50 μm) provides bulk wear resistance. This localized differentiation resolves the contradiction between thin overall layer and sufficient wear protection.
3Duration of action of stationary object
If nitrocarburizing is performed to increase service life, then the component can withstand high frictional forces, but dimensional changes occur affecting manufacturing precision
Solution Approach 1:
The patent controls dimensional changes by optimizing nitrocarburizing parameters: temperature range (500-550°C), time (2-8 hours), and medium selection (salt bath or gas). These controlled parameter changes achieve the desired layer thickness (connecting layer 4-16 μm, diffusion layer ≥50 μm) while minimizing excessive dimensional changes, thus resolving the contradiction between service life extension and manufacturing precision.
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 provides improved abrasive and adhesive wear resistance, increased operational reliability, and reduced dimensional changes, ensuring high service life and reliability of the axial piston machine components.
Implementation Method 1
In this heat treatment method, the chemical composition of the marginal layer is changed, such that the strength is increased and the wear behavior is improved
Implementation Method 2
nitrocarburizing in gas or in a salt bath
Implementation Method 3
In this heat treatment method, the chemical composition of the marginal layer is changed
Data Source
AI summary
A method is provided for forming wear-resistant layer on the surface of cylinder bores a cylinder drum of a hydrostatic axial piston machine within which a respective piston is moved in a manner subject to intensive wear. The cylinder bores are gas nitrocarburized in two stages to minimize the wear and include a thin uniform connecting layer that has a thickness of 4 to 16 μm and a comparatively thick underlying diffusion layer.