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Used to observe the δ-Ni in the nickel-iron-based superalloy structure 3 Metallographic etchant for Nb phase and method of use thereof

A high-temperature alloy, nickel-iron-based technology, applied in the field of high-temperature alloy materials, can solve the problems of inability to develop delta phase, poor corrosion uniformity of the substrate, etc., and achieve the effects of clear appearance, large contrast, and good chemical stability.

Active Publication Date: 2016-11-16
CHINA HUANENG GRP CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The traditional superalloy metallographic etchant is mainly aimed at the microstructure development of nickel-based superalloys. If the corrosion is strong, it is easy to dissolve the δ phase in the nickel-iron-based alloy. If the corrosion is weak, the δ phase cannot be corroded. Visualization under light microscope and scanning electron microscope
Using electrolytic corrosion, the uniformity of matrix corrosion is often poor

Method used

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  • Used to observe the δ-Ni in the nickel-iron-based superalloy structure <sub>3</sub> Metallographic etchant for Nb phase and method of use thereof
  • Used to observe the δ-Ni in the nickel-iron-based superalloy structure <sub>3</sub> Metallographic etchant for Nb phase and method of use thereof
  • Used to observe the δ-Ni in the nickel-iron-based superalloy structure <sub>3</sub> Metallographic etchant for Nb phase and method of use thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] The nickel-iron-based superalloy GH4169 alloy was corroded. The alloy uses γ' and γ″ / δ phases as high-temperature strengthening phases. The content of Fe in the alloy is 18-19% (mass fraction), and the content of Nb is 5.0-5.5% (mass fraction). The γ″ obtained by aging treatment -Ni 3 Nb transforms into its thermodynamically stable state δ-Ni during long-term (service) use 3 Nb phase, and aggregated to grow. figure 1 with figure 2 In order to use this corrosive agent to corrode the metallographic surface after long-term (service) mechanical polishing of GH4169 alloy, the (long) needle-shaped δ-Ni 3 The Nb phase is clearly visible; at the same time, the intragranular spherical γ' phase and the precipitated carbides at the grain boundaries are also clearly visible under the scanning electron microscope.

Embodiment 2

[0030] The IN718 alloy has been corroded, such as image 3 shown. After low-temperature aging treatment of IN718 alloy (the chemical composition is basically the same as that of GH4169 alloy), a small amount of δ-Ni is precipitated at the grain boundary 3 Nb phase, due to δ-Ni 3 The Nb phase has a small amount of precipitation and a small size, and is distributed in the grain boundary, so it is extremely difficult to observe. After using this etchant to corrode the mechanically polished metallographic surface, a small amount of (short) acicular δ-Ni distributed perpendicular to the grain boundaries can be clearly observed by scanning electron microscope 3 Nb phase.

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Abstract

The invention discloses a metallographical corrosive for observing delta-Ni3Nb phase in a ferronickel-based superalloy structure and a using method of the metallographical corrosive. The metallographical corrosive comprises the following components by volume fraction: 26-33% of hydrochloric acid, 30-37% of nitric acid, 13-18% of hydrofluoric acid and 12-31% of ethyl alcohol; every 100 mL of the metallographical corrosive contains 2g of oxalic acid and 1g of copper sulfate; the mass percentage concentration of the hydrochloric acid is 36%; the mass percentage concentration of the nitric acid is 68%; the mass percentage concentration of the hydrofluoric acid is 40%; the copper sulfate is anhydrous copper sulfate; the ethyl alcohol is anhydrous ethyl alcohol; and the selected chemical reagents are analytical reagents. The using method comprises the following steps: coating the prepared metallographical corrosive on the metallographical surface of a ferronickel-based superalloy sample; chemically corroding for 5-8 seconds; washing and drying the metallographical corrosive on the metallographical surface by clear water and alcohol; and observing the delta-Ni3Nb phase in the microscopic structure through an optical microscope and a scanning electron microscope.

Description

technical field [0001] The invention belongs to the field of superalloy materials, and in particular relates to a method for observing δ-Ni in nickel-iron-based superalloy structure. 3 Metallographic etchant for Nb phase and method of use thereof. Background technique [0002] Nickel-iron-based superalloys have good high-temperature strength, good processability and economy, and have important applications in high-temperature components in aerospace, energy, and petrochemical fields. The microstructure of the alloy is closely related to the performance of the alloy. The observation and analysis of its phase precipitation and microstructure evolution characteristics have important guiding significance for the design of alloy composition and performance decay after long-term service. [0003] The matrix of nickel-iron-based superalloys is austenite γ phase, and γ′ and γ" phases are used as the main strengthening phases. After long-term service, γ" tends to tend to δ(Ni 3 Nb)...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23F1/30C23F1/28G01N1/32
Inventor 尹宏飞赵新宝鲁金涛袁勇党莹樱杨珍
Owner CHINA HUANENG GRP CO LTD
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