Spark Plug Electrode Material With Ni Oxide Oxidation Barrier
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Solution Overview
Problem
Iridium (Ir) alloy spark plug electrodes face challenges with high-temperature oxidation resistance due to the volatility of Ir oxides, leading to shorter lifespan compared to platinum plugs, especially in harsh engine environments with lean combustion, high EGR systems, and high power/rotation speed/compression ratio designs.
Innovation Solution
A spark plug electrode material featuring a substrate of Ir or Ir alloy with a Ni oxide antioxidant film, where the Ni film is converted to Ni oxide through heat treatment, providing a thickness of 3.0 µm to 8.0 µm to suppress oxidation and volatilization, and an underlying Au layer for adhesion and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Ir or Ir alloy is used as electrode material to achieve thinner electrode shape and good ignition efficiency, then ignition/combustion efficiency is improved, but high-temperature oxidation resistance deteriorates due to volatility of Ir oxides
Solution Approach 1:
A Ni film is introduced as an intermediary protective layer between the Ir electrode material and the oxidizing environment. The Ni film oxidizes preferentially to form NiO, which acts as a barrier preventing oxygen from reaching and oxidizing the Ir substrate, thereby protecting the electrode while maintaining its ignition functionality
Solution Approach 2:
The invention creates a composite structure consisting of the Ir electrode material combined with a Ni protective film layer. This composite material leverages the excellent electrical and ignition properties of Ir while adding the oxidation protection capabilities of Ni/NiO, resolving the contradiction between ignition efficiency and oxidation resistance
2Reliability
If alloy composition is optimized by adding precious metals like Pt or Rh to improve high-temperature oxidation resistance, then oxidation resistance is improved, but manufacturing cost increases
Solution Approach 1:
Instead of using expensive precious metals for alloying, the invention employs a Ni film that serves as a sacrificial protective layer. The Ni film is relatively inexpensive and can be applied through cost-effective plating processes, providing oxidation protection without the high material costs associated with Pt or Rh alloys
Solution Approach 2:
The invention changes the approach from modifying the bulk alloy composition to applying a surface coating with specific thickness parameters (3.0 μm to 8.0 μm). This parameter-based solution allows control of oxidation resistance through film thickness rather than expensive alloying, reducing manufacturing costs while maintaining reliability
3Reliability
If Ni film thickness is increased to enhance oxidation protection, then high-temperature oxidation resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention establishes specific parameter ranges for the Ni film thickness (3.0 μm to 8.0 μm) that optimize both protection effectiveness and manufacturability. Within this range, the film provides sufficient oxidation barrier properties without requiring excessive thickness control precision or adding unnecessary manufacturing complexity
Solution Approach 2:
The Ni film thickness is designed to be sufficient but not excessive (3.0-8.0 μm range). This partial action approach provides adequate oxidation protection without the diminishing returns and increased complexity associated with much thicker films, balancing effectiveness with manufacturability
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 Ni oxide film significantly enhances high-temperature oxidation resistance, reducing Ir consumption and extending the lifespan of spark plug electrodes by inhibiting oxygen diffusion and maintaining effectiveness even in extreme conditions.
Implementation Method 1
an antioxidant film being a Ni film having a thickness of 3.0 μm or more and 8.0 μm or less... the antioxidant film may be Ni oxide
Implementation Method 2
the Ni film is converted to Ni oxide through heat treatment
Implementation Method 3
providing a thickness of 3.0 µm to 8.0 µm to suppress oxidation and volatilization... by inhibiting oxygen diffusion
Data Source
Figure 1
AI summary
The present invention discloses a spark plug electrode material including a substrate formed of Ir or Ir alloy, and an antioxidant film covering a surface of the substrate. Here, an underlying layer formed of Au is formed on a surface of the substrate formed of Ir or Ir alloy, and on the underlying layer, a Ni film having a thickness of 3.0 µm or more and 8.0 µm or less is formed as an antioxidant film. The Ni film turns into an antioxidant film formed of Ni oxide in an oxidizing atmosphere at 500°C or higher. Owing to the antioxidant film, the spark plug electrode material of the present invention has an excellent high-temperature oxidation property.