Metal Nitride Coated Fasteners for High-Temperature Anti-Locking
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Solution Overview
Problem
Conventional fastening members used in high-temperature equipment, such as those in thermal power plants, tend to lock due to prolonged exposure to high temperatures and loads, leading to increased inspection times and costs, as they deteriorate through oxidation, corrosion, and diffusion-bonding, with existing techniques designed for room temperature environments failing to address these issues effectively.
Innovation Solution
A fastening member with a hard metal nitride layer formed on its threaded surfaces using the physical vapor deposition method, made from materials like ferritic heat-resistant steel or Ni-based superalloys, providing excellent high-temperature strength, oxidation resistance, and wear resistance, which prevents locking by maintaining a low friction coefficient and allowing easy loosening with standard tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fastening members are used in high-temperature environments, then they provide initial fastening strength, but they lock due to oxidation, corrosion, and diffusion-bonding over time
Solution Approach 1:
The patent applies a hard layer made of metal nitride specifically on the threaded portion surfaces where male and female threads contact each other. This localized treatment provides oxidation resistance and low friction coefficient exactly where needed to prevent locking, while the base material maintains its fastening strength. The hard layer has different properties (hardness, oxidation resistance, friction characteristics) than the base material, creating local quality differentiation that solves the contradiction between maintaining fastening strength and preventing locking.
2Duration of action of moving object
If fastening members are exposed to high temperature and load stress for long periods, then they maintain fastening function, but the loosening agent reacts with fastening members causing locking
Solution Approach 1:
The patent converts the harmful effect of high-temperature oxidation into a beneficial outcome by applying a hard layer of metal nitride that is specifically resistant to oxidation. The hard layer acts as a protective barrier that prevents oxygen from reaching and reacting with the base material and loosening agent. By converting the oxidation-prone surface into an oxidation-resistant surface through the hard layer coating, the patent eliminates locking caused by chemical reactions while maintaining long-term fastening function.
3Reliability
If conventional fastening members are designed for room temperature use, then they prevent corrosion at room temperature, but they fail to address high-temperature locking mechanisms
Solution Approach 1:
The patent changes the surface properties of the fastening member by applying a hard layer made of metal nitride with specific characteristics: high hardness, oxidation resistance, and low friction coefficient. This parameter change in surface properties enables the fastening member to withstand high-temperature environments without locking. The hard layer's physical and chemical parameters (hardness, oxidation resistance, friction coefficient) are specifically selected to address high-temperature conditions, making the fastening member adaptable to a wider temperature range while maintaining corrosion resistance.
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 ensures that fastening members do not stick together, allowing for easy removal with standard tools, reducing inspection time and costs, and maintaining performance over long periods at temperatures exceeding 500°C by inhibiting oxidation and wear.
Implementation Method 1
A hard layer made of a metal nitride is formed on a surface of a threaded portion of the male thread or a surface of a threaded portion of the female thread
Data Source
AI summary
A fastening member in an embodiment consists of a bolt and a nut. A hard layer made of a metal nitride is formed on a surface of a threaded portion of the bolt or a surface of a threaded portion of the nut.