Method for detecting depth of nitriding layer of titanium alloy
Through chemical solution erosion polishing and microscopic observation, the accuracy of the depth detection of nitriding layer of titanium alloy is solved, and the significant color difference detection between the nitriding layer and the substrate is realized. It is suitable for titanium alloys with a variety of nitriding treatments.
Patent Information
- Application Number
- CN202510277724.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-10
- Publication Date
- 2025-07-11
AI Technical Summary
The prior art is difficult to accurately detect the depth of the nitriding layer of titanium alloy, especially because the nitriding layer is shallow and cannot be detected by the hardness gradient method, and ordinary mixed acid solutions cannot clearly distinguish the nitriding layer from the substrate.
The chemical solution erosion polishing method was used to make the nitriding layer and the substrate show different color differences through two erosive agent treatments. The depth of the nitriding layer was observed using an optical microscope and the scale was used to measure the depth of the nitriding layer.
Accurate detection of the depth of the nitriding layer is achieved, suitable for gas nitriding, ion nitriding and nitrogen-carbon nitriding layers of titanium alloys, avoiding the shortcomings of the hardness gradient method and providing a clear measurement of the thickness of the nitriding layer.
Smart Images
Figure CN120293638A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of detection, and relates to a method for detecting the nitriding layer depth of titanium alloy. Background Art
[0002] Titanium alloy has two significant advantages of high specific strength and good corrosion resistance, and has excellent properties such as high specific strength, high fatigue performance, high corrosion resistance, low expansion coefficient, and high stability, and has good application prospects in the aerospace field.
[0003] Due to the disadvantages of low surface strength, low thermal conductivity, and poor wear resistance of titanium alloy, adhesion and biting are likely to occur during the assembly process of titanium alloy components, and then component failure or even fracture occurs. In order to improve the wear resistance of titanium alloy, surface modification treatment by nitriding is carried out to increase the surface strength, thereby improving the service life of the components.
[0004] Nitriding forms titanium nitride on the surface of titanium alloy. The nitride has high hardness and does not reduce the corrosion resistance at the same time. The depth of the nitriding layer is detected by etching with a conventional hydrofluoric acid solution for titanium alloy, but it is difficult to distinguish the nitriding layer and the matrix; the hardness gradient method has certain requirements for detecting the nitriding depth of titanium alloy, but the nitriding layer of titanium alloy is often relatively shallow and cannot be detected by the hardness gradient method. Summary of the Invention
[0005] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, and providing a method for detecting the nitriding layer depth of titanium alloy. After chemically etching and polishing the nitrided surface of titanium alloy, the different corrosion resistances of the nitriding layer and the matrix are utilized to show different colors, so as to distinguish the nitriding layer and the matrix layer by color, and the depth of the nitriding layer can be accurately detected.
[0006] The solution for the present invention to solve the technical problem is:
[0007] A method for detecting the nitriding layer depth of titanium alloy, comprising:
[0008] Slow wire electrical discharge machining is used to cut the nitrided titanium alloy part to expose the cross-section with the nitriding layer on the outer surface, and a cross-section sample is obtained;
[0009] The cross-section sample is subjected to sample embedding treatment to obtain the to-be-ground sample after embedding;
[0010] The to-be-ground sample is subjected to grinding and polishing treatment to obtain the to-be-etched sample;
[0011] Prepare the first etching reagent;
[0012] Prepare the second etching reagent;
[0013] The to-be-etched sample is cleaned with alcohol; the surface of the to-be-etched sample is wiped with the first etching reagent; the first etched sample is obtained;
[0014] Wipe the surface of the first etched specimen with a second etching reagent; obtain a second etched specimen;
[0015] Observe the etched surface of the second etched specimen and detect the case depth.
[0016] In the above method for detecting the case depth of a titanium alloy nitriding layer, after grinding and polishing the specimen to be ground, the surface of the specimen to be ground is smooth and has no obvious scratches.
[0017] In the above method for detecting the case depth of a titanium alloy nitriding layer, the first etching reagent is composed of hydrofluoric acid, nitric acid, and deionized water; the ratio is HF:HNO3:H2O=(0.3 - 5):(2 - 10):100.
[0018] In the above method for detecting the case depth of a titanium alloy nitriding layer, the second etching reagent is composed of ammonium bifluoride and deionized water; the ratio is NH4HF2:H2O=(50 - 100):100.
[0019] In the above method for detecting the case depth of a titanium alloy nitriding layer, dip a cotton ball in the first etching reagent and wipe the surface of the specimen to be etched, and the wiping time is 5 - 10 s.
[0020] In the above method for detecting the case depth of a titanium alloy nitriding layer, after obtaining the first etched specimen, wipe and clean the surface of the first etched specimen with alcohol and blow it dry.
[0021] In the above method for detecting the case depth of a titanium alloy nitriding layer, dip a cotton ball in the second etching reagent and wipe the surface of the specimen to be etched, and the wiping time is 5 - 10 s.
[0022] In the above method for detecting the case depth of a titanium alloy nitriding layer, after obtaining the second etched specimen, wipe and clean the surface of the second etched specimen with alcohol and blow it dry.
[0023] In the above method for detecting the case depth of a titanium alloy nitriding layer, use an optical microscope to observe the etched surface of the second etched specimen, and magnify the surface case position of the etched surface by 200 - 500 times for observation.
[0024] In the above method for detecting the case depth of a titanium alloy nitriding layer, when detecting the case depth with a scale, change the detection positions 3 - 5 times.
[0025] The beneficial effects of the present invention compared with the prior art are:
[0026] (1) Aiming at the problem that the hardness gradient method cannot be used to detect the nitriding layer of titanium alloy and the ordinary mixed acid solution cannot clearly distinguish the nitriding layer from the matrix, the present invention proposes a method for detecting the case depth of the titanium alloy nitriding layer;
[0027] (2) The present invention uses an etchant to first etch the substrate and the nitriding layer, and then uses an etchant to etch again, so that the nitriding layer is bright white and clearly distinguished from the substrate, and has a clear boundary, thereby effectively measuring the thickness of the titanium alloy nitriding layer through a ruler;
[0028] (3) The present invention is applicable to the detection of gas nitriding, ion nitriding and nitrogen-carbon nitriding layer depth of titanium alloy;
[0029] (4) The present invention adopts the metallographic method, which is suitable for detecting the depth of various penetration layers of titanium alloys, and effectively avoids the problem that the hardness gradient method cannot be used for accurate measurement due to the small depth of the penetration layer. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 This is a flow chart of the titanium alloy nitriding layer depth detection of the present invention;
[0031] Figure 2 This is a graph showing the results of nitriding depth detection of titanium alloy according to the present invention. DETAILED DESCRIPTION
[0032] The present invention will be further described below in conjunction with the embodiments.
[0033] The present invention provides a method for detecting the depth of nitriding layer of titanium alloy. A smooth titanium alloy surface is obtained by grinding and polishing, and a chemical solution is used to erode the nitriding surface of the polished titanium alloy. Different corrosion resistances of the nitriding layer and the substrate are used to display different colors, so that the nitriding layer and the substrate layer are distinguished by color, and the depth of the nitriding layer can be accurately detected.
[0034] The detection method of the nitriding layer depth of titanium alloy is as follows: Figure 1 As shown, the specific steps include:
[0035] The titanium alloy nitrided parts were cut by slow wire cutting to expose the section with nitrided layer on the outer surface and obtain the section sample.
[0036] The cross-section sample is mounted to obtain the mounted sample to be ground.
[0037] The sample to be ground is subjected to grinding and polishing treatment. After the grinding and polishing treatment, the surface of the sample to be ground is smooth without obvious scratches, and the sample to be eroded is obtained.
[0038] Prepare the first etching reagent.
[0039] The first etching reagent comprises hydrofluoric acid, nitric acid and deionized water; the ratio is HF:HNO3:H2O=(0.3-5):(2-10):100.
[0040] Prepare the second etching reagent.
[0041] The second etching reagent comprises ammonium bifluoride and deionized water; the ratio is NH4HF2:H2O=(50-100):100.
[0042] Clean the sample to be etched with alcohol; wipe the surface of the sample to be etched with the first etch reagent; obtain the first etch sample. Use a cotton ball to dip the first etch reagent and wipe the surface of the sample to be etched for 5-10 seconds. After obtaining the first etch sample, wipe and clean the surface of the first etch sample with alcohol and blow dry.
[0043] Wipe the surface of the first erosion sample with the second erosion reagent to obtain the second erosion sample. Use a cotton ball dipped in the second erosion reagent to wipe the surface of the sample to be eroded for 5-10 seconds. After obtaining the second erosion sample, clean the surface of the second erosion sample with alcohol and blow dry.
[0044] The erosion surface of the second erosion sample was observed to detect the depth of the seepage layer.
[0045] The specific method is: use an optical microscope to observe the erosion surface of the secondary erosion sample, and magnify the surface penetration layer position of the erosion surface by 200-500 times for observation. When using a ruler to detect the penetration layer depth, change 3-5 positions for detection. The test results are as follows: Figure 2 shown.
[0046] Example 1
[0047] 1. Use wire cutting to cut the TC4 titanium alloy nitrided parts to expose the section with nitriding layer on the outer surface.
[0048] 2. Mount the cross-section sample in step 1 to obtain the mounted sample to be ground.
[0049] 3. The sample to be ground in step 2 is subjected to grinding and polishing treatment to make the surface of the sample to be ground smooth without obvious scratches, thereby obtaining the sample to be eroded.
[0050] 4. Prepare etching reagent 1. The ingredients of etching reagent 1 are hydrofluoric acid, nitric acid, and deionized water. The ratio is HF: HNO3: H2O = 4:6:100.
[0051] 5. Prepare etching reagent 2. The ingredients of etching reagent 2 are ammonium bifluoride and deionized water, and the ratio is NH4HF2:H2O=80:100.
[0052] 6. Clean the sample to be etched in step 3 with alcohol and blow it dry quickly. Dip a cotton ball in the etch reagent in step 4) and wipe the surface of the sample to be etched for 6 seconds. Clean the surface of the etched sample with alcohol and blow it dry to obtain a first etched sample.
[0053] 7. Dip a cotton ball into the etching reagent 2 in step 5 and wipe the surface of the first etching sample in step 6 for 5 seconds. Clean the surface of the first etching sample with alcohol and blow dry quickly to obtain a second etching sample.
[0054] 8. Use an optical microscope to observe the erosion surface of the secondary erosion sample 7, find the location of the surface penetration layer, and magnify it by 200 times. Use a ruler to detect the depth of the penetration layer, and change 3 positions to detect the depth of the penetration layer.
[0055] Example 2
[0056] 1. Use wire cutting to cut the TA2 titanium alloy nitrided parts to expose the section with nitriding layer on the outer surface.
[0057] 2. Mount the cross-section sample in step 1 to obtain the mounted sample to be ground.
[0058] 3. The sample to be ground in step 2 is subjected to grinding and polishing treatment to make the surface of the sample to be ground smooth without obvious scratches, thereby obtaining the sample to be eroded.
[0059] 4. Prepare etching reagent 1. The ingredients of etching reagent 1 are hydrofluoric acid, nitric acid, and deionized water. The ratio is HF:HNO3:H2O=0.5:3:100.
[0060] 5. Prepare etching reagent 2. The ingredients of etching reagent 2 are ammonium bifluoride and deionized water, and the ratio is NH4HF2:H2O=75:100.
[0061] 6. Clean the sample to be etched in step 3 with alcohol and blow it dry quickly. Use a cotton ball dipped in the etching reagent in step 4 to wipe the surface of the etched sample for 5 seconds. Clean the surface of the etched sample with alcohol and blow it dry to obtain a first etched sample.
[0062] 7. Dip a cotton ball into the etching reagent 2 in step 5 and wipe the surface of the first etching sample in step 6 for 6 seconds. Clean the surface of the first etching sample with alcohol and blow dry quickly to obtain a second etching sample.
[0063] 8. Use an optical microscope to observe the erosion surface of the secondary erosion sample 7, find the location of the surface penetration layer, and magnify it 300 times. Use a ruler to detect the depth of the penetration layer, and change 3 positions to detect the depth of the penetration layer.
[0064] The present invention aims to solve the problem that the nitriding layer of titanium alloy cannot be detected by hardness gradient method and common mixed acid solution cannot clearly distinguish the nitriding layer from the substrate, and proposes a method for detecting the depth of the nitriding layer of titanium alloy; the present invention adopts an etchant to corrode the substrate and the nitriding layer first, and then adopts an etchant to corrode again, so that the nitriding layer is bright white and can be clearly distinguished from the substrate with clear boundaries, so that the thickness of the nitriding layer of titanium alloy can be effectively measured by a ruler.
[0065] The present invention is applicable to the detection of the nitriding layer depth, ion nitriding layer depth and nitrocarburizing layer depth of titanium alloys;
[0066] The present invention adopts the metallographic method and is applicable to the detection of various nitriding layer depths of titanium alloys, effectively avoiding the problem that the hardness gradient method cannot be accurately used for measurement due to the small nitriding layer depth.
[0067] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.
Claims
1. A method for detecting the nitrided layer depth of a titanium alloy, characterized in that: Including: Using slow wire cutting to slice the titanium alloy parts after nitriding, exposing the cross-section with nitrided layer on the outer surface to obtain a cross-section specimen; Performing embedding treatment on the cross-section specimen to obtain the specimen to be ground after embedding; Performing grinding and polishing treatment on the specimen to be ground to obtain the specimen to be etched; Preparing the first etching reagent; Preparing the second etching reagent; Cleaning the specimen to be etched with alcohol; wiping the surface of the specimen to be etched with the first etching reagent to obtain the first etched specimen; Wiping the surface of the first etched specimen with the second etching reagent to obtain the second etched specimen; Observing the etched surface of the second etched specimen to detect the depth of the nitrided layer.
2. The detection method for the nitriding layer depth of a titanium alloy according to claim 1, characterized in that: After performing grinding and polishing treatment on the specimen to be ground, the surface of the specimen to be ground is smooth and has no obvious scratches.
3. The detection method of the nitrided layer depth of a titanium alloy according to claim 1, characterized in that: The first etching reagent consists of hydrofluoric acid, nitric acid and deionized water; the ratio is HF:HNO3:H2O=(0.3-5):(2-10):
100.
4. The detection method for the nitriding layer depth of a titanium alloy according to claim 1, characterized in that: The second etching reagent consists of ammonium bifluoride and deionized water; the ratio is NH4HF2:H2O=(50-100):
100.
5. The detection method for the nitriding case depth of a titanium alloy according to claim 1, wherein: Dipping a cotton ball in the first etching reagent and wiping the surface of the specimen to be etched for 5-10 s.
6. The detection method of the nitriding case depth of a titanium alloy according to claim 5, characterized in that: After obtaining the first etched specimen, wiping and cleaning the surface of the first etched specimen with alcohol and drying it.
7. A method for detecting the nitriding layer depth of a titanium alloy according to claim 1, characterized in that: Dipping a cotton ball in the second etching reagent and wiping the surface of the specimen to be etched for 5-10 s.
8. A method for detecting the nitrided layer depth of a titanium alloy, according to claim 7, characterized in that: After obtaining the second etched specimen, wiping and cleaning the surface of the second etched specimen with alcohol and drying it.
9. The detection method for the nitriding layer depth of a titanium alloy according to claim 1, characterized in that: Observing the etched surface of the second etched specimen with an optical microscope, and magnifying the surface nitrided layer position of the etched surface by 200-500 times for observation.
10. The detection method for the nitriding case depth of a titanium alloy according to claim 9, characterized in that: When detecting the depth of the nitrided layer with a scale, changing 3-5 positions for detection.