A kind of electrochemical etchant showing the metallographic structure of SLM formed in 718 nickel-based superalloy and its application method

Abstract

The invention relates to the technical field of metallographic detection and analysis of high-temperature alloys. The invention discloses an electrochemical etchant for displaying the metallographic structure of SLM formed IN 718 nickel-based superalloy. The electrochemical etchant is composed of an electrolytic etchant and a cold chemical etchant, including the following Volume fraction of raw materials: electrolytic corrosion agent is perchloric acid 10 ~ 20ml, absolute ethanol 80 ~ 90ml; cold chemical corrosion agent is absolute alcohol 30 ~ 40ml, deionized water 30 ~ 40ml, concentrated nitric acid 8 ~ 10ml, concentrated hydrochloric acid 24 ~ 30ml. The electrochemical etchant of the invention is convenient to configure, and the corrosion steps are easy to operate, which not only reduces the risk of thermochemical corrosion, but also greatly improves the corrosion effect under the premise of ensuring the corrosion quality.

Description

technical field [0001] The invention relates to the technical field of metallographic detection and analysis of superalloys, in particular to an electrochemical etchant for displaying the metallographic structure of SLM formed IN 718 nickel-based superalloys and a method for using the same. Background technique [0002] IN 718 alloy (international designation: NiCr19Fe19Nb5Mo3), as a precipitation-strengthened nickel-based deformed alloy, uses "solid solution strengthening" to precipitate the γ' phase (Ni 3 (Al,Ti,Nb)) and the body-centered tetragonal γ″ phase (Ni 3 Nb) as the main strengthening phase, on the one hand, by combining the characteristics of dispersed and uniform nucleation, coherent, fine particles and small spacing, and low phase interface energy due to the small mismatch between the γ' phase and the matrix lattice, the IN The 718 alloy has high yield, high toughness, high fatigue resistance, and high creep resistance. On the other hand, it has a non-coherent...

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Problems solved by technology

Since the IN 718 nickel-based superalloy has a large amount of Ni and Cr elements, the surface of the material will be covered with a dense oxide film after forming and has strong corrosion resistance. The corrosion method cannot break the oxide film on the surface and corrode the metal phase (for example: aqua regia corrosion method (concentrated HCl and concentrated HNO 3 The mixed solution whose volume ratio is 3:1), three-acid solution corrosion method (the volume fraction ratio is 80% HCl, 13% HF, 7% HNO 3 mixed solution)), while the thermal chemical etching method formed by heating the etching solution on the basis of the cold chemical etching method can obtain the metallographic structure of the material (for example: 80mlHCl+4mlHNO 3 +1gCuCl+20ml glycerol, or 15mlHCl+15mlH 2 o 2 +1.5gCuSO 4 Heating in a water bath to 80°C to 90°C for 0.5 to 1 hour before corrosion), but because the heating temperature and heating time are difficult to grasp during the heating process, excessive metallographic corrosion is prone to occur, and at the same time, the volatility is unstable Acidic corrosive liquid has a high risk during heating, so an electrochemical etchant and its application method for displaying the metallographic structure of SLM-formed IN 718 nickel-based superalloy are now proposed

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