Multilayer DLC Roller Coating for Wind Turbine Bearing Wear
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Self-aligning roller bearings for wind power generators face premature wear and reduced service life due to axial loads, which conventional DLC coatings struggle to address effectively, especially with film peeling issues.
Innovation Solution
A self-aligning roller bearing design featuring a multilayer DLC coating with a base layer of Cr and WC, a mixed layer of WC and DLC, and a top layer with a gradient hardness structure, applied to rollers with a surface roughness optimized for adhesion and wear resistance, eliminating the need for high-viscosity lubricants and enhancing peeling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer DLC coating is applied on the rollers, then wear resistance is improved, but film peeling occurs reducing coating durability
Solution Approach 1:
The DLC coating is divided into multiple layers (first DLC layer, second DLC layer, and intermediate layer) instead of using a single-layer coating. This segmentation allows each layer to have different properties: the first DLC layer provides wear resistance, the second DLC layer maintains hardness, and the intermediate layer prevents peeling by having lower hardness and better adhesion to the roller surface.
Solution Approach 2:
The coating system uses composite material structure combining DLC (diamond-like carbon) with an intermediate layer of different material properties. The intermediate layer has lower hardness than the DLC layers, creating a gradient structure that bridges the hard DLC coating and the roller surface, preventing stress concentration and film peeling while maintaining the wear resistance of the outer DLC layers.
2Reliability
If high-viscosity lubricants are used to improve oil film formation, then lubrication performance is improved, but maintenance complexity increases
Solution Approach 1:
The patent replaces the reliance on high-viscosity lubricants (mechanical/chemical solution) with a DLC coating system (surface engineering solution). The DLC coating provides inherent wear resistance and lubrication properties through its low friction coefficient and hard surface, eliminating the need for high-viscosity lubricants and reducing maintenance requirements.
3Strength
If DLC coating film thickness is increased to improve wear resistance, then mechanical strength is improved, but peeling resistance decreases
Solution Approach 1:
The thick DLC coating is segmented into multiple layers with the intermediate layer acting as a buffer. This allows the total coating thickness to be sufficient for wear resistance while the intermediate layer prevents peeling by reducing stress concentration at the coating-substrate interface.
Solution Approach 2:
The composite coating structure with the softer intermediate layer creates a gradient from hard outer DLC layers to the intermediate layer, which acts as a stress-absorbing transition zone. This composite structure maintains peeling resistance even with increased total coating thickness by distributing mechanical stresses across layers with different properties.
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 multilayer DLC coating significantly improves wear resistance and mechanical strength, extends bearing service life, and facilitates lean lubrication with reduced maintenance needs, while preventing peeling and maintaining excellent adhesion to the base material.
Implementation Method 1
DLC stands for diamond-like carbon
Implementation Method 2
a base layer directly formed on the surfaces of the rollers and mainly containing Cr and WC, a mixed layer formed on the base layer and mainly containing WC and DLC, and a top layer formed on the mixed layer and mainly containing DLC
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a self-aligning roller bearing for supporting a main shaft of a wind power generator, the self-aligning roller bearing including an inner ring, an outer ring, two rows of rollers, and retainers. Each of the rollers has an outer peripheral surface formed with a DLC coating having a multilayer structure. The DLC coating has a film thickness of 2.0 µm or larger. A base material of each of the rollers has an external surface having a surface roughness of Ra ≤ 0.3 and RΔq ≤ 0.05. The DLC coating having the multilayer structure includes layers having stepwisely increasing film hardnesses such that a layer situated closer to outside has a higher hardness.