Hearth Roll Thermal Spray Coating With Uniform Cr7C3 Dispersion
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Solution Overview
Problem
Existing thermal spray powders used for hearth rolls in heat treatment furnaces are prone to oxidation and have 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 uniform chromium carbide dispersion, providing high temperature hardness, oxidation resistance, and thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thermal spray powder produced by granulation sintering method is used, then the powder has small primary particles and large specific surface area, but the thermal spray coating is likely to be oxidized early
Solution Approach 1:
The invention changes the production method from granulation sintering to gas atomization, fundamentally altering the powder's physical parameters. Gas atomization produces spherical particles with controlled porosity and optimized surface area, reducing oxidation susceptibility while maintaining sprayability and coating performance
Solution Approach 2:
The invention uses a composite powder structure containing Cr7C3 chromium carbide particles dispersed in a nickel-based alloy matrix. This composite structure provides both the hardness from chromium carbide and the oxidation resistance from the nickel-based alloy, while the specific atomization process optimizes the distribution and morphology of the composite particles
2Strength
If thermal spray powder with chromium carbide and heat-resistant alloy is used, then hardness is improved, but chromium carbide distribution is uneven and hardness varies partially
Solution Approach 1:
The gas atomization process changes the physical parameters of powder production, creating spherical particles with uniform internal structure. This process ensures homogeneous distribution of Cr7C3 chromium carbide particles within the nickel-based alloy matrix, eliminating the uneven distribution and hardness variation problems associated with granulation sintering methods
Solution Approach 2:
The invention achieves homogeneous distribution of chromium carbide particles throughout the alloy matrix through the gas atomization process. The spherical particle morphology and controlled cooling rate during atomization ensure uniform dispersion of Cr7C3 particles, resulting in consistent hardness throughout the thermal spray coating without localized soft spots
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 formed using the atomized powder exhibits improved hardness, oxidation resistance, and thermal shock resistance, reducing pickup and buildup on hearth rolls, thereby enhancing production efficiency.
Implementation Method 1
a thermal spray coating is provided on the surface of each hearth roll
Implementation Method 2
a Cr7C3 phase dispersed in the heat-resistant alloy phase
Implementation Method 3
exhibits improved hardness, oxidation resistance, and thermal shock resistance
Implementation Method 4
exhibits improved hardness, oxidation resistance, and thermal shock resistance
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.