Cubic Boron Nitride Hard Chromium Layer Tribological Wear
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Solution Overview
Problem
Existing hard chromium layers in tribological systems, such as those used in motor vehicle engines, suffer from increased wear on cylinder surfaces and inadequate fire safety, leading to burn marks and increased oil consumption, despite reduced piston ring wear.
Innovation Solution
A tribological system with a hard chromium layer containing cubic boron nitride particles of average size 0.1 to 0.3 μm, embedded in cracks within the layer, applied to an iron-based substrate, enhancing wear resistance and fire safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hard chromium layer contains diamond particles (0.25 to 0.5 μm) as hard material particles, then piston ring wear is reduced, but cylinder surface wear increases
Solution Approach 1:
The invention changes the particle size parameter from the conventional 0.25-0.5 μm diamond particles to cubic boron nitride particles with size 0.06-0.15 μm. This parameter change in both material type and particle size resolves the contradiction by reducing cylinder wear while maintaining piston ring wear resistance.
2Reliability
If hard chromium layer contains silicon carbide particles, then wear resistance is improved, but fire trace resistance becomes insufficient
Solution Approach 1:
The invention changes the hard material particle from silicon carbide to cubic boron nitride, and changes the particle size to 0.06-0.15 μm. Cubic boron nitride has superior thermal resistance properties that prevent fire mark formation while the optimized particle size maintains wear resistance, thus resolving both requirements simultaneously.
3Ease of manufacture
If hard material particles are larger than 1 μm, then they can be incorporated into the hard chromium layer, but they contribute to greater wear in the tribological system
Solution Approach 1:
The invention optimizes the particle size parameter to 0.06-0.15 μm, which is small enough to be effectively incorporated into the hard chromium layer matrix during galvanic deposition, yet large enough to provide wear resistance. This optimal size range prevents the greater wear that occurs with particles larger than 1 μm while ensuring proper incorporation.
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 system significantly reduces wear on both piston rings and cylinder surfaces while improving fire safety, with cubic boron nitride's high thermal resistance and optimal particle size contributing to these benefits.
Implementation Method 1
a hard chromium layer, which is formed by galvanic deposition from an electrolyte containing hexavalent chromium
Implementation Method 2
the hard material particles being formed from cubic boron nitride and an average particle size of 0.1 to 0.3 μm
Data Source
AI summary
The present invention relates to a hard chrome layer, which is formed substantially by electrodeposition from an electrolyte containing a hexavalent chrome and which has fissures in which particles of hard material are intercalated. According to the invention, it is provided that the particles of hard material are formed from cubic boron nitride and have an average particle size of from 0.1 to 1.0 µm. The present invention also relates to a substrate with such a hard chrome layer and to a tribological system comprising a basic body and an opposing body in the form of such a substrate.