Method for etching surface crack defect of sample

Abstract

The invention provides a method for etching a surface crack defect of a sample. The method comprises the following steps: (I) conducting electrolytic polishing with the voltage of 50 to 60v on the cracked sample for 65 to 75s, and socking the polished cracked sample in an etchant for 20 to 120s, wherein the etchant is a 2 to 5% nitric alcohol solution; (II) slightly moving the sample in the etching process to ensure that the etchant flows slowly on the ground surface of the sample to promote overflow of bubbles, and taking out the sample after the ground surface turns dark; (III) soaking the sample into anhydrous ethanol, and moving an observation surface slightly, wherein the step (III) can be carried out repeatedly for cleaning till foul and impurities near cracks are removed; (IV) after cleaning, taking out the sample, and finally, carefully wiping the etched surface with medical absorbent cotton. The method provided by the invention has the advantages that the accuracy and the reliability of a test result are greatly improved; the operation is simple; the time consumption is low; the method is one of effective methods for re-test of samples with crack defects.

Description

technical field [0001] The invention relates to a metallographic corrosion method, in particular to a method for corroding crack defects on the surface of a sample. Background technique [0002] Metallographic analysis is one of the important means of testing and analyzing materials. It aims to reveal the real structure of materials. In industrial production, metal components and mechanical parts will be damaged due to various reasons. These damages will follow the metal components and parts. The use of cracks that develop into microcracks or expand into macrocracks will eventually cause the parts to break and fail. Therefore, crack analysis is an important part of component failure analysis and inference. [0003] In metallographic experiments, samples for cracks are usually divided into two types, namely, polished state and corroded state. The purpose of further corroding the polished state sample is to observe its microstructure, so as to analyze the origin and direction ...

AI Technical Summary

Problems solved by technology

However, for cracked samples, because there are gaps of different depths on the surface, when the sample is taken out from the etchant and rinsed and dried, a part of the chemical reagent and water still remain in the cracks, and as time goes on , the residue will continue to seep out, causing the observation surface near the crack to rust and the original appearance of the structure cannot be observed; it can be seen that the level of metallographic sample preparation of the cracked sample determines the failure to a large extent. The degree to which the analysis conclusion is correct

[0004] Considering the defects of the existing crack corrosion method, people have made improvements in many aspects, such as changing the sample taken from the etchant from the traditional cold water rinse to hot water rinse, and shortening the crack as much as possible in the laboratory. Corrosion time of the sample, finding and improving the best drying angle of the sample, etc., but still not well solved the key problems such as residue leakage near the crack and rust around the crack