Metallographic phase corrosive liquid for austenitic stainless steel as well as preparation and corrosion methods thereof

Abstract

The invention provides a novel metallographic phase corrosive liquid for high temperature resistance and fatigue resistance 304 austenitic stainless steel. The metallographic phase corrosive liquid ischaracterized by being prepared from the following raw materials in percentage by mass: 7-9 percent of hydrofluoric acid, 12-16 percent of concentrated nitric acid, 1-2 percent of boracic acid and the balance of distilled water, wherein the mass concentration of the hydrofluoric acid is 40 percent, the mass concentration of the nitric acid is 60-65 percent, and the mass concentration of the boracic acid is 1-3 percent. The corrosive liquid is simple in preparation, convenient in operation of corrosion method, small in pollution and good in stability and reproducibility and can rapidly, uniformly and clearly display a metallographic structure; and a corrosion method is simple in step, convenient to operate and strong in practicability.

Description

technical field [0001] The invention belongs to the field of metallographic corrosion of austenitic stainless steel, in particular to a metallographic corrosion solution for austenitic stainless steel containing molybdenum, copper, niobium and cobalt in its components and a preparation and corrosion method thereof. Background technique [0002] Stainless steel is divided into three categories according to its metallographic structure: austenitic stainless steel, ferritic stainless steel, and martensitic stainless steel. Among them, austenitic stainless steel accounts for the largest proportion, and its output accounts for 70% of the output of stainless steel, so it is widely used. In the research and application of austenitic stainless steel, it is often necessary to analyze its structure type, and adjust its composition, processing and heat treatment process in time according to the structure analysis results. However, in terms of the corrosion of metallographic samples, m...

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Problems solved by technology

However, the effect of aqua regia corrosion on austenitic stainless steel depends on the processing state of the alloy. The corrosion effect on the cast and annealed products is good, but the corrosion effect on the cold-worked state is not ideal, and the grain boundary is not obvious.

And the corrosion process has extremely high requirements on the operator's operation process, the corrosion time is short, the grain boundary is not obvious, the corrosion time is slightly longer, the grain boundary becomes coarse and blurred; and the aqua regia corrosion solution must be used after 24 hours after preparation, the corrosion solution The stability of the corrosive liquid is poor, and it cannot be stored for a long time. After a long time, the corrosive solution will become invalid.

[0005] There are some other corrosive agents for austenitic stainless steel. Some documents provide a formula of 10-40mlHNO 3 +3~10ml 48%HF+25~50ml H 2 O etchant, the use temperature is 70-80°C (160-180°F), the sample is immersed in the etchant until the desired degree of corrosion is obtained, but the etchant needs to be heated in a fume hood, which is very dangerous , and the erosion effect is also unknown

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