Fine-Grained Diaphragm for Hydrogen-Resistant Pressure Sensors
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Solution Overview
Problem
Pressure sensors exposed to harsh conditions, such as high temperatures and chemically aggressive substances like hydrogen, face issues with thermal expansion and hydrogen penetration, leading to inaccurate measurements and potential structural failure.
Innovation Solution
A pressure sensor with a diaphragm made of fine-grained austenitic iron-nickel-cobalt alloy with a thermal expansion coefficient of less than 9.0*10^-6 K^-1 and a grain diameter of less than 20 µm, combined with a hydrogen-resistant coating, to mitigate thermal expansion and hydrogen ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If metallic materials with high nickel content (austenitic microstructure) are used for the diaphragm to achieve low thermal expansion coefficient, then thermal expansion is reduced, but hydrogen penetration increases due to large grain diameter
Solution Approach 1:
The patent changes the grain diameter parameter from significantly greater than 20 μm to less than 20 μm through controlled cooling after hot forming. This parameter change maintains the low thermal expansion coefficient of the austenitic microstructure while dramatically reducing hydrogen penetration by eliminating continuous grain boundary pathways.
Solution Approach 2:
The patent creates a composite microstructure by combining the austenitic phase (for low thermal expansion) with fine grain boundaries (for hydrogen barrier properties). The resulting material exhibits both low thermal expansion and high hydrogen resistance, effectively combining benefits of different microstructural characteristics.
2Measurement precision
If the diaphragm is made thin to increase pressure measurement sensitivity, then measurement sensitivity improves, but structural strength decreases
Solution Approach 1:
The patent changes the grain diameter parameter to less than 20 μm, which fundamentally alters the strength-to-thickness ratio of the diaphragm material. This enables the diaphragm to be made thinner for improved sensitivity while maintaining sufficient strength through the fine-grained microstructure's inherent mechanical properties.
3Stability of the object's composition
If austenitic microstructure with large grain diameter is used, then low thermal expansion is achieved, but material properties become anisotropic complicating design
Solution Approach 1:
The patent changes the grain diameter parameter to less than 20 μm, which transforms the material behavior from anisotropic to effectively isotropic. This simplifies design calculations and structural-mechanical simulations while preserving the low thermal expansion properties of the austenitic microstructure.
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 accurate pressure measurements at high temperatures while preventing hydrogen penetration, maintaining structural integrity and reducing manufacturing complexity and costs.
Implementation Method 1
If the medium contains hydrogen, hydrogen can penetrate the membrane. A hydrogen-containing medium has a hydrogen content of at least 1 vol%. Particularly with the average grain diameter of significantly more than 20 μm in the austenitic structure of the iron-nickel-cobalt alloy material number 1.3981 and the iron-nickel-cobalt alloy UNS number N19909, hydrogen can relatively easily penetrate the interior of the pressure sensor along the grain boundaries and accumulate there.
Implementation Method 2
At such high temperatures, differences in the coefficients of thermal expansion of the pressure sensor's components become detrimental. These differing coefficients of thermal expansion manifest themselves as a temperature influence on the zero value (TK0) and as a temperature influence on the characteristic value (TKE).
Data Source
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AI summary
The invention relates to a pressure sensor (1) for measuring the pressure (P2) of a liquid or gaseous medium (2), which medium (2) contains hydrogen and is located in a measuring chamber (20); which pressure sensor (1) is arranged on the measuring chamber (20) and is continuously exposed to a temperature (T1) of up to 350°C during measurement; which pressure sensor (1) comprises a diaphragm (12) and a sensor element (13); wherein the diaphragm (12) protects the sensor element (13) from direct contact with the medium (2); wherein the pressure (P2) acts on the sensor element (13) via the diaphragm (12) and the sensor element (13) generates a measured value (M) under the influence of the pressure (P2); wherein the diaphragm (12) is made of a metallic material (30) with a coefficient of thermal expansion (α30) of less than or equal to 9.0 × 10⁻⁶ K⁻¹; wherein a mean grain diameter (31) of the metallic material (30) is less than 20pm.