Chemical polishing method for titanium alloy high-power sample

Abstract

The invention relates to a chemical polishing method of a titanium alloy high-power sample, in particular to a corrosive agent for chemical polishing of a titanium alloy metallographic high-power sample and an operation method of the corrosive agent. According to the chemical polishing method, the daily working intensity can be effectively relieved, and the production efficiency is greatly improved. And the chemical polishing method is not limited by the shape and the size of a sample, so that the requirement on the original smoothness of a polished surface is not high, a layer change is not generated on the polished surface, and high-power inspection can be directly performed on general detection without re-corrosion after polishing is completed. The chemical polishing method is mainly used for high-power metallographic detection of large titanium alloy forgings in the fields of aviation, aerospace, weaponry, industrial machinery and the like.

Description

Technical field:

[0001] The invention relates to a chemical polishing method, in particular to a chemical polishing method for a titanium alloy high-magnification sample. Background technology:

[0002] In metallographic testing, all high-magnification samples need to be polished to obtain a polished surface, and the polished surface must be properly corroded before its high-magnification microstructure can be displayed under an optical microscope. In actual operations at this stage, mechanical polishing is the most common polishing method and is widely used in the polishing process of various alloy materials. However, mechanical polishing has very obvious disadvantages, such as difficulty in actual operation, long time consumption, and the polishing agent often contains toxic carcinogens such as CrO3, which is extremely harmful to human health. Chemical polishing, as an optional alternative to mechanical polishing, can effectively reduce the intensity of daily work and greatly improve production efficiency. In addition, since the chemical polishing method is not limited by the shape and size of the sample, it does not require high finish of the original grinding surface, and the polished surface does not produce delamination. After polishing, general inspections can be directly carried out at high magnification without further corrosion.

[0003] Chinese invention patent CN107164765A published on September 15, 2017 discloses a titanium alloy polishing liquid. The polishing liquid includes the following components by mass fraction: 200 parts of lactic acid, 200 parts of methanol, 50 parts of propylene glycol, 5 parts of barium fluoride, 2 parts of sodium stearate, 2 parts of saccharin, 2 parts of benzotriazole, and 1000 parts of deionized water. The titanium alloy polishing liquid can make the titanium alloy surface free of lines and can obtain a mirror light effect. However, in actual applications, it is found that the configuration process of the polishing liquid is complicated, the cost is high, and the polishing effect is not good. It cannot be applied on a large scale in actual production. Summary of the invention:

[0004] The technical problem to be solved by the present invention is to provide an efficient, safe and easy-to-operate chemical polishing method for titanium alloy metallographic high-magnification samples, so that the chemical polishing of titanium alloy metallographic high-magnification samples can be carried out under conditions that are not suitable for mechanical polishing or other conditions, so as to achieve the purpose of high-magnification tissue detection.

[0005] In order to solve the above technical problems, the present invention provides a chemical polishing method for titanium alloy high-magnification samples. The chemical polishing method of the present invention requires materials and equipment including: 100 ml of HF solution; 100 ml of HNO3 solution; titanium alloy sample; fume hood with good ventilation conditions, etc.

[0006] Since the NO released during the reaction of the mixed solution of hydrofluoric acid and nitric acid with titanium alloy is a toxic gas, the test process must be carried out in a fume hood to ensure air circulation. Mix 100 ml of HF solution and 100 ml of HNO3 solution evenly at a ratio of 1:1 as the polishing solution. Place the test specimen to be polished, which has been pre-ground with 1000# or finer sandpaper, with the surface to be detected facing up in a plastic container. Then pour the prepared polishing solution into the container. The amount of the polishing solution should be such that the liquid level is about 2 mm above the upper surface of the specimen, and immediately start shaking or stirring the solution vigorously. The polishing process begins. When the solution reacts violently and releases a large amount of yellow NO2 gas, start timing. After 10 seconds, immediately dilute the polishing solution with a large amount of clear water and rinse the specimen in the container.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0008] For high-magnification specimens of general metal parts, generally, first use a grinding wheel and sandpaper to polish until a mirror surface appears, then use a mechanical method to complete the polishing with the assistance of a general polishing agent, and finally place it under an electron microscope to observe its high-magnification metallographic structure. However, due to the high hardness and excellent corrosion resistance of titanium alloy materials. The traditional mechanical polishing method is difficult to operate and takes a long time. Ordinary polishing agents have poor corrosion effects on titanium alloys, and ordinary polishing agents contain a large amount of toxic and carcinogenic substances such as CrO3, which cause great harm to the human body.

[0009] This chemical polishing method has the following advantages compared with the currently commonly used mechanical polishing method: simple operation, fast speed, and high efficiency. After polishing, it can meet the needs of general metallographic high-magnification inspection without the need for chemical corrosion again, especially for rapid analysis, and can reduce the chamfering phenomenon of the specimen. In addition, the chemical polishing method also has certain advantages in the detection of workpieces with irregular shapes, workpieces that are not suitable for sampling and destruction, and large workpieces. Specific implementation method:

[0010] The following further illustrates the present invention in conjunction with embodiments.

[0011] Embodiment:

[0012] Specimen material: TC27

[0013] Phase transformation point: 882.5 °C, quantity 2

[0014] Specimen size: radius 1 cm, height 3 cm, small cylinder.

[0015] Cutting weight: Specimen 1: 44.3 g; Specimen 2: 44.8 g

[0016] Step 1: Preliminary grinding

[0017] Hold the specimen by hand and grind the upper surface of the cylinder on a grinding wheel to remove the oxide skin.

[0018] Step 2: Sandpaper polishing to obtain a mirror surface

[0019] First, use relatively coarse sandpaper to polish unidirectionally. Hold the specimen tightly with 3 fingers (thumb + index finger + middle finger). Do not apply too much force in the vertical direction. When there is only one-directional mark, rotate the specimen by 90 degrees. Then use finer sandpaper to polish unidirectionally. When the marks made in the first polishing completely disappear and there are completely and evenly one-directional marks on the upper surface of the specimen, change to even finer sandpaper, rotate the specimen by 90 degrees, and continue the above steps until the sandpaper reaches 1000 mesh, and the specimen is polished and ready for use.

[0020] Step 3: Chemical polishing

[0021] Prepare 100 ml of HF solution; 100 ml of HNO3 solution; 2 polished titanium alloy specimens; a fume hood with good ventilation conditions, etc. Since the NO released when the mixture of hydrofluoric acid and nitric acid reacts with the titanium alloy is a toxic gas, the test process must be carried out in the fume hood to ensure air circulation. Further, discuss the gas components generated using chemical equations:

[0022] 3T i +12HF + 4HNO3 = 3T i F4 + 8H2O + 4NO↑

[0023] Mix 100 ml of HF solution and 100 ml of HNO3 solution evenly in a 1:1 ratio as the polishing solution. Place the specimen to be polished, which has been pre-polished with 1000# or finer sandpaper, with the surface to be tested facing up in a plastic container. Then pour the prepared polishing solution into the container. The amount of the polishing solution should be such that the liquid level is about 2 mm higher than the upper surface of the specimen, and immediately start shaking or stirring the solution vigorously. The polishing process begins. When the solution reacts violently and releases a large amount of yellow NO2 gas, start timing. After 10 seconds, immediately dilute the polishing solution with a large amount of water and rinse the specimen in the container. Further, discuss the gas components generated using chemical equations:

[0024] 2NO + O2 = 2NO2↑

[0025] Step 4: Metallographic analysis

[0026] Drop several drops of alcohol on the surface of the polished specimen, and blow it dry with a hair dryer on the cold air setting. Then place the specimen under an electron microscope (1000 times magnification) for metallographic analysis.

[0027] Table 1 Measured data of the examples

[0028] Specimen Maximum overall dimension (mm) Net weight (g) High magnification condition (1000x) Remarks Sample 1 10×10×30.2 44.2 Grain boundaries are clear and grains are complete Qualified Sample 2 10×10×30.5 44.8 Grain boundaries are clear and grains are complete Qualified

Claims

1. A chemical polishing method for high magnification specimens of titanium alloy, characterized in that, It includes the following steps: preliminary grinding, sandpaper grinding to a mirror surface, chemical polishing, and metallographic inspection.

2. The chemical polishing method for high magnification specimens of titanium alloy according to claim 1, characterized in that, The raw materials of the polishing liquid required for chemical polishing are HF solution and HNO3 solution.

3. The chemical polishing method for the high-magnification specimen of titanium alloy according to claim 1 or 2, characterized in that, The mixing ratio of the two raw materials is 1:

1.

4. The chemical polishing method for the high magnification specimen of titanium alloy according to claim 1, characterized in that, The titanium alloy is TC27.

5. The chemical polishing method for high-magnification specimens of titanium alloy according to claim 1, characterized in that, It must be carried out in a fume hood.