Nickel Plating Adhesion on Spark Plug Metal Shell
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Solution Overview
Problem
The existing spark plug designs face issues with the nickel plating layer peeling off due to stress during the bending process, leading to reduced corrosion resistance.
Innovation Solution
A nickel plating layer with specific characteristics, including an average value in a monochrome image of 170 to 230, and crystal grains with controlled cross-sectional areas, lengths, and aspect ratios, is applied to the metal shell to enhance adhesion and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nickel plating layer is applied to the metal shell surface before fixing, then corrosion resistance is improved, but the plating layer peels off due to bending stress
Solution Approach 1:
The invention changes the physical parameters of the nickel plating layer by controlling crystal grain size (average 0.03μm to 0.1μm) and crystal orientation (preferential orientation of (100) plane within ±15 degrees). This parameter control allows the plating layer to maintain adhesion during bending while preserving corrosion resistance
Solution Approach 2:
The invention creates a composite structure where the nickel plating layer is integrated with the metal shell base material. The controlled crystal grain structure and orientation create a composite-like behavior that combines the ductility needed for bending with the corrosion resistance of the nickel plating
2Reliability
If the nickel plating layer is made thick to improve corrosion resistance, then adhesion deteriorates due to bending stress
Solution Approach 1:
Instead of increasing thickness, the invention changes the microstructural parameters of the plating layer: controlling crystal grain size to 0.03μm-0.1μm and establishing preferential (100) orientation within ±15 degrees. This allows adequate corrosion protection with thinner, more adherent plating
Solution Approach 2:
The invention shifts from controlling plating thickness (one dimension) to controlling crystal grain size and orientation (microstructural dimensions). This dimensional shift enables better adhesion while maintaining corrosion resistance
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
An adhesion of a nickel plating layer to a metal shell is improved, and an effect of improving a corrosion resistance by providing the nickel plating layer is sufficiently exerted. A spark plug 1 includes a cylindrical metal shell 3 that extends in an axial CL1 direction, and a nickel plating layer 31 that is made of metal containing nickel as a main component and covers an outer surface of the metal shell. In a monochrome image of 256 gradations where black is 0 and white is 255, which is obtained by observing a cross-section perpendicular to an outer surface of the nickel plating layer by a transmission electron microscope with an acceleration voltage of 200 kV, an average value in 256 gradations of the monochrome image is 170 or larger and 230 or smaller.