Expanded Magnet Coating Structure for High-Temperature Corrosion Resistance
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Solution Overview
Problem
Existing expandable coatings for rare earth permanent magnet synchronous motors lack sufficient thermal stability and mechanical performance at high temperatures, leading to potential damage and reduced corrosion resistance under centrifugal forces and high operational temperatures.
Innovation Solution
An expanded coating with a specific microstructure comprising spheroid pores and a filler resin, where the spheroid pores occupy 50%-60% of the cross-sectional area, and a combination of chemical and physical foaming agents is used, providing enhanced thermal stability and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional expandable coatings are used, then the coating can be expanded by thermal treatment to fill the magnetic steel groove, but the coating lacks sufficient thermal stability and mechanical performance at high temperatures (>150°C), leading to potential damage under centrifugal force
Solution Approach 1:
The patent uses a composite coating system comprising an expandable coating layer and a heat-resistant coating layer. The heat-resistant coating layer contains inorganic fillers (alumina, silica, zirconia) and heat-resistant resins that provide thermal stability and mechanical strength at high temperatures, while the expandable coating layer provides expansion capability to fill the magnetic steel groove. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent modifies the coating composition by incorporating heat-resistant resins (polyimide, phenolic resin, epoxy resin) and inorganic fillers in specific proportions. The weight ratio of inorganic filler to heat-resistant resin is controlled within 9:1 to 1:1, and the total content of heat-resistant resin and inorganic filler is maintained at 80-99.9 wt%. These parameter changes enable the coating to maintain mechanical strength and thermal stability at temperatures above 150°C.
2Reliability
If the expanded coating has relatively poor thermal stability, then the coating may be sheared along the magnetic steel groove under centrifugal force, but improving thermal stability is needed to prevent damage
Solution Approach 1:
The heat-resistant coating layer acts as a protective barrier that prevents the expandable coating from direct exposure to high-temperature environments and centrifugal forces. The inorganic fillers (alumina, silica, zirconia) provide structural integrity and resistance to shear stress, while the heat-resistant resins provide adhesion and flexibility. This composite structure ensures coating integrity under centrifugal force at high temperatures.
Solution Approach 2:
The patent applies different coating layers with specific local functions: the expandable coating layer provides expansion and filling capability in the groove, while the heat-resistant coating layer provides thermal and mechanical protection on the outer surface. Each layer is optimized for its specific function, with the heat-resistant layer containing higher concentrations of inorganic fillers and heat-resistant resins to handle the harsh operating conditions.
3Volume of stationary object
If the coating is designed with high expansion capability, then the coating can effectively fill the magnetic steel groove, but the mechanical performance and corrosion resistance at high temperatures need to be improved
Solution Approach 1:
The expandable coating layer contains expandable microspheres that provide high expansion capability to fill the magnetic steel groove effectively. The heat-resistant coating layer containing inorganic fillers and heat-resistant resins provides corrosion resistance and thermal stability. The combination of these two layers resolves the contradiction by allowing the inner layer to expand while the outer layer protects against corrosion and high temperatures.
Solution Approach 2:
The expandable coating layer utilizes expandable microspheres that create a porous structure upon expansion, enabling the coating to fill the magnetic steel groove effectively. The porous structure provides high expansion volume while maintaining connectivity with the substrate. The heat-resistant coating layer then seals and protects this porous structure from corrosion and thermal degradation.
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 coating exhibits improved shear strength, tensile strength, oil resistance, and neutral salt spray performance at 170°C, with shear strength greater than 2 MPa and neutral salt spray performance exceeding 288 hours, ensuring durability and reliability in high-temperature environments.
Implementation Method 1
The expandable coatings can be expanded by thermal treatment to fill a magnetic steel groove, thus fixing the magnetic steel pieces
Implementation Method 2
the expandable powder comprises a prepolymer, a curing agent, at least one functional filler, and a foaming agent
Implementation Method 3
the foaming agent is a chemical foaming agent. The foaming agent does not prematurely react with the substrate of the coating
Implementation Method 4
the expandable powder comprises a prepolymer, a curing agent
Implementation Method 5
the expandable coating material comprises a thermosetting resin
Data Source
AI summary
The present disclosure provides an expanded coating, a preparation method and use thereof, and a permanent magnet comprising same. The expanded coating described herein comprises pores and a filler resin arranged among the pores; the pores comprise at least a spheroid pore having a cross section with a long diameter and a short diameter; in the cross section of the expanded coating, the area of the spheroid pores accounts for 50%-60% of the cross-sectional area of the expanded coating. The permanent magnet of the present disclosure comprises the expanded coating. The expanded coating has high strength and can exhibit excellent mechanical properties and corrosion resistance at high temperatures (such as 170° C.), with a shear strength greater than 2 MPa, a tensile strength greater than 2 MPa, an oil resistance greater than 1800 h and a neutral salt spray performance greater than 288 h at 170° C.