Atomized Hearth Roll Coating for Oxidation and Buildup Resistance
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Solution Overview
Problem
Thermal spray coatings used in heat treatment furnaces for hearth rolls are prone to oxidation and uneven chromium carbide distribution, leading to early surface oxidation, buildup, and pickup issues, which reduce production efficiency.
Innovation Solution
An atomized powder with a specific composition, including a heat-resistant alloy phase and Cr7C3 phase, is used to form a thermal spray coating with improved high-temperature hardness, oxidation resistance, and thermal shock resistance, featuring a Co-based alloy phase and a needle-like Cr7C3 structure, applied using the atomization method to ensure uniform dispersion and reduced porosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal spray powder produced by granulation sintering method is used, then the coating can be formed, but the coating is likely to be oxidized early due to porous structure and large specific surface area
Solution Approach 1:
The invention changes the production method from granulation sintering to atomization process, fundamentally altering the microstructure parameters of the thermal spray powder. This produces a dense, fine-grained structure with reduced porosity and smaller specific surface area, thereby improving oxidation resistance of the coating
Solution Approach 2:
The invention creates a composite thermal spray powder consisting of chromium carbide particles embedded in a heat-resistant alloy matrix. This composite structure provides both the hardness of chromium carbide and the oxidation resistance of heat-resistant alloy, while the atomization process ensures uniform distribution and dense packing
2Strength
If thermal spray powder with chromium carbide and heat-resistant alloy is used, then high temperature hardness can be achieved, but the chromium carbide distribution is uneven and hardness varies locally
Solution Approach 1:
The atomization process changes the physical and chemical parameters of powder formation, enabling uniform mixing of chromium carbide and heat-resistant alloy at the molecular level before solidification. This results in homogeneous chromium carbide distribution throughout the alloy matrix, eliminating local hardness variations
Solution Approach 2:
The invention merges chromium carbide particles with heat-resistant alloy in a single atomized powder structure, creating a unified composite material where both components are uniformly distributed. This integrated approach ensures consistent hardness throughout the coating rather than having separate zones of different properties
3Reliability
If thermal spray coating is applied to prevent buildup, then steel plate quality can be maintained, but production efficiency decreases due to frequent cleaning stops
Solution Approach 1:
The atomized powder produces a coating with optimized microstructural parameters including fine grain size, dense structure, and uniform chromium carbide distribution. These parameter improvements enhance the coating's anti-buildup performance and durability, extending the operational period between cleanings and thereby maintaining production efficiency
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 thermal spray coating exhibits excellent high-temperature hardness, oxidation resistance, and thermal shock resistance, reducing the occurrence of pickup and buildup on hearth rolls, and the laser treatment further enhances the coating's toughness and uniformity, improving production efficiency.
Implementation Method 1
a thermal spray coating is provided on the surface of each hearth roll
Implementation Method 2
the laser treatment further enhances the coating's toughness and uniformity
Data Source
AI summary
An atomized powder has a heat-resistant alloy phase and a Cr7C3 phase dispersed in the heat-resistant alloy phase, and contains 20 to 46% of Ni, 22 to 43% of Cr, 4 to 13% of Al, 0.1 to 1.0% of Y, and 0.3 to 4.2% of C on a mass basis, and a remainder thereof includes Co and unavoidable impurities.