Co-Carbide Composite Coating for High-Temperature Transfer Rollers
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Solution Overview
Problem
Existing high-temperature material transferring members face issues with build-up resistance, wear resistance, and oxidation resistance, particularly in high-temperature gas atmospheres above 1100°C, leading to indentation defects and reduced durability.
Innovation Solution
A composite coating film with a Co-based alloy powder and Cr carbide is applied using a plasma powder overlaying process, optimizing the content of C, Si, Cr, and Co to enhance peelability, oxidation resistance, and wear resistance, while controlling the microstructure to prevent cracking and maintain strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating film is formed on the surface of base metal to prevent sticking, then sticking resistance is improved, but build-up resistance deteriorates due to local adhesion of peeled-off material and oxide
Solution Approach 1:
The invention uses a composite coating film containing Cr carbide particles (20-70 vol%) dispersed in a metal matrix. The Cr carbide provides hard particles that prevent build-up adhesion, while the metal matrix ensures coating integrity and sticking resistance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The coating film creates a localized hard surface layer with Cr carbide particles on the roller surface, while the base metal retains its original properties. This localized modification provides build-up resistance at the contact surface without affecting the overall roller structure, resolving the contradiction between sticking resistance and build-up prevention.
2Strength
If a hard coating film is formed to improve wear resistance, then wear resistance is improved, but cracking occurs during cooling after plasma powder overlay
Solution Approach 1:
The invention controls the carbon content in the alloy powder within a specific range (0.03-0.6 mass%) to optimize the microstructure of the coating film. By adjusting compositional parameters, the coating achieves sufficient hardness for wear resistance while maintaining microstructural stability during cooling, preventing crack formation.
Solution Approach 2:
The coating film creates a localized hard surface layer with Cr carbide particles on the roller surface, while the base metal retains its original properties. This localized modification provides build-up resistance at the contact surface without affecting the overall roller structure, resolving the contradiction between sticking resistance and build-up prevention.
3Reliability
If overlay welding is performed to form a heat resistant coating film, then oxidation resistance is improved, but the coating film becomes brittle and cracks during thermal cycling
Solution Approach 1:
The invention optimizes the compositional parameters of the alloy powder, specifically controlling C content (0.03-0.6 mass%), Si content (0.2-3 mass%), Cr content (22-35 mass%), and Co content (>50 mass%). These parameter adjustments create a coating film with balanced oxidation resistance and thermal shock resistance, preventing crack formation during thermal cycling.
Solution Approach 2:
The coating film is formed as a composite material with Cr carbide particles dispersed in a Co-based metal matrix. This composite structure provides both oxidation resistance from the Cr-containing matrix and thermal shock resistance from the controlled microstructure, resolving the contradiction between oxidation resistance and thermal cycling stability.
4Reliability
If Cr or Ni alloy is selected as base metal to improve sticking resistance, then sticking resistance is improved, but build-up resistance remains insufficient
Solution Approach 1:
The invention applies a composite coating film containing Cr carbide particles (20-70 vol%) on the base metal surface. The Cr carbide provides hard particles that prevent build-up adhesion, while the metal matrix ensures coating integrity and sticking resistance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The coating film is formed as a distinct layer segmented from the base metal, with Cr carbide particles distributed throughout the metal matrix. This segmentation allows the coating to provide specialized build-up resistance functions while the base metal provides structural support and sticking resistance, resolving the contradiction between the two requirements.
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 effectively prevents build-ups and indentation defects, ensuring long-term durability and improved quality of hot working products, with enhanced wear and oxidation resistance, thus extending the life of transfer rollers and reducing production costs.
Implementation Method 1
a composite coating film of Co-based alloy-Cr carbide which is formed by a plasma powder overlaying process
Implementation Method 2
enhanced wear and oxidation resistance
Implementation Method 3
sticking may occur between the high-temperature material and the transferring member
Implementation Method 4
enhanced wear and oxidation resistance
Data Source
Figure 1
AI summary
A high-temperature material transferring member including a coating film formed on a surface of base metal, wherein the coating film is a composite coating film using a mixed powder made up of: a Co-based alloy powder containing, in mass%, 0.03 to 0.6% of C, 0.2 to 3% of Si, 22 to 35% of Cr, and more than 50% of Co; and a Cr carbide powder, the composite coating film is formed by the plasma powder overlaying process. The high-temperature material transferring member has excellent build-up resistance particularly in a gas atmosphere of 1100°C or more. The high-temperature material transferring member has excellent in build-up resistance, oxidation resistance, and heat cracking resistance.