Thermal Sprayed Coating for Sliding Member Seizure Resistance
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Solution Overview
Problem
Thermal sprayed coatings with chromium for sliding members suffer from reduced peeling resistance due to oxide formation, leading to increased friction, lubrication failure, and potential seizure, as the metallic bond between droplets is broken by manganese oxides, resulting in contamination and weight increase in cylinder blocks.
Innovation Solution
An iron-based thermal sprayed coating with chromium and silicon, where the oxide content is limited to 1 mass% or less, using non-oxidizing gases during spraying to prevent oxide formation and enhance metallic bonding, resulting in a uniform and strong coating with improved seizure resistance and corrosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium is added to the thermal sprayed coating to improve corrosion resistance, then corrosion resistance is improved, but peeling resistance is reduced due to oxide formation breaking metallic bonds between droplets
Solution Approach 1:
The invention changes the chemical composition parameters by adding silicon (0.03-5 mass%) to the coating material, which modifies the oxidation behavior and reduces oxide formation. This parameter change allows maintaining chromium content for corrosion resistance while improving peeling resistance through reduced oxide interference at droplet interfaces
Solution Approach 2:
The invention creates a composite coating material containing iron, chromium, and silicon elements. The multi-element composition works synergistically where chromium provides corrosion resistance and silicon suppresses oxide formation, resolving the contradiction between corrosion resistance and peeling resistance that exists in single-element or two-element coatings
2Weight of stationary object
If thermal sprayed coating is used instead of cast iron liner, then weight of cylinder block is reduced, but bonding strength between droplets is reduced due to oxide formation
Solution Approach 1:
By adding silicon to the coating material composition and controlling its content within 0.03-5 mass%, the invention modifies the oxidation characteristics during thermal spraying. This parameter change reduces oxide formation at droplet surfaces, thereby improving bonding strength while maintaining the weight reduction benefit of thermal sprayed coating over cast iron liners
Solution Approach 2:
The invention creates a protective atmosphere during thermal spraying by using silicon to suppress oxidation reactions. The silicon acts as an oxidation inhibitor, creating a reduced oxide environment at the droplet interfaces, which enables strong metallic bonding without requiring vacuum or inert gas conditions
3Strength
If manganese is added to prevent decrease in bonding strength, then oxidation of iron and chromium is reduced, but oxide formation on droplet surfaces still occurs and intervenes in interfaces
Solution Approach 1:
The invention changes the chemical composition by adding silicon (0.03-5 mass%) which has different oxidation characteristics compared to manganese. Silicon suppresses oxide formation on droplet surfaces more effectively while maintaining bonding strength, resolving the contradiction between preventing oxidation and avoiding surface oxide formation that interferes with droplet interfaces
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 achieves superior seizure resistance and corrosion protection by maintaining a metallic bond between droplets, reducing oxide interference and enhancing bonding strength, while maintaining lubrication and preventing weight increase in cylinder blocks.
Implementation Method 1
a thermal sprayed coating is formed on an inner circumferential surface of a cylinder bore
Implementation Method 2
bonding strength between thermal sprayed droplets that form the thermal sprayed coating
Implementation Method 3
A stainless steel-based thermal sprayed coating that contains chromium (Cr) is prevented from being corroded by low-quality fuel that contains a large amount of sulfur
Implementation Method 4
the thermal sprayed droplets have surfaces on which manganese oxides are formed, and oxides intervene in interfaces between the thermal sprayed droplets
Implementation Method 5
the oxides break a metallic bond between the thermal sprayed droplets, and bonding strength between the thermal sprayed droplets is not sufficiently obtained
Data Source
AI summary
A sprayed coating for a sliding member of the present invention includes a ferrous alloy containing iron (Fe) as a major ingredient.The sprayed coating for the sliding member containing 10 mass % or more and 20 mass % or less of chromium (Cr), and 0.1 mass % or more and 0.5 mass % or less of silicon (Si) and having the content rate of an oxide in the sprayed coating of 1 area % or less has corrosion resistance with improved seizure resistance.