β-type and near-β-type titanium alloy β-phase transformation pitting corrosion agents, their preparation methods and applications

Abstract

This invention relates to the field of physicochemical testing technology, specifically to β-type and near-β-type titanium alloy β-phase transformation point corrosion agents, their preparation methods, and applications. The β-type and near-β-type titanium alloy β-phase transformation point corrosion agents comprise agent A and agent B. Agent A is prepared from the following raw materials in volume parts: 1-10 parts hydrofluoric acid, 5-10 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water. Agent B is a 10-20 wt% NH4HF2 solution. This invention also discloses the preparation method and application of the β-type and near-β-type titanium alloy β-phase transformation point corrosion agents. The β-type and near-β-type titanium alloy β-phase transformation point corrosion agents of this invention can reduce the appearance of pseudophases such as corrosion "pits" and "black spots," improve α-phase contrast, enhance the accuracy of determining the content of primary α-phase, and simultaneously improve the accuracy of evaluating β-phase and near-β-phase transformation points, reducing the corrosion and operational difficulty of titanium alloy metallographic testing.

Description

Technical Field

[0001] This invention relates to the field of physical and chemical testing technology, specifically to β-type and near-β-type titanium alloy β-phase transformation point corrosion agents, their preparation methods, and applications. Background Technology

[0002] Beta-type titanium alloys are high-melting-point, high-strength alloys that readily exhibit metastable beta single-phase structure during normalizing or tempering. The main alloying elements in these beta-type titanium alloys are beta-stabilizing chemical elements such as molybdenum, chromium, and vanadium. Near-beta-type titanium alloys refer to titanium alloys with beta-stabilizing element content slightly higher than the critical concentration (the lowest concentration that allows the high-temperature beta phase to be retained to room temperature during rapid cooling), mainly including grades such as β-Ⅲ and BT22. The beta phase transformation point detection primarily determines the beta phase transformation temperature of titanium alloys based on the α phase content; therefore, the key to beta phase transformation point detection is that the α phase must be clearly and without interference.

[0003] Because both β-type and near-β-type titanium alloys exhibit pseudo-phases resembling the α-phase morphology due to corrosion effects, the assessment of β-phase transformation pitting corrosion is difficult and can even lead to erroneous results. Currently, the main method for β-type titanium alloy phase transformation pitting corrosion testing is the use of etchants provided in GB / T 5168-2008 "Test Method for High and Low Magnification Microstructure of α-β Titanium Alloys": 2%–5% (v / v) chemically pure hydrofluoric acid (40%–42% (w / w)); 10%–12% (v / v) chemically pure nitric acid (65%–68% (w / w)); the remainder being water. However, in actual testing, this etchant easily forms pseudo-phases such as corrosion "pits" and "black spots" on the corrosion surface of β-type titanium alloys, such as… Figure 1 As shown, in β-type and near-β-type titanium alloys, the background of the phase transformation point sample is basically pure gray-white β phase or metastable β phase, which makes corrosion prone to forming "pits". The formation of "pits" and "black spots" is related to the original microstructure and corrosion conditions of the sample. Usually, in β-type and near-β-type quenched samples, due to different etchant formulations, inconsistent or untimely gas dissipation during corrosion, "pits" and "black spots" will form on the sample surface. The "pits" are similar in morphology to the α phase and are difficult to distinguish, while the "black spots" will cover the α phase. For the phase transformation point detection of β and near-β titanium alloys, this will seriously interfere with the determination of the primary α phase content, thus affecting the determination of the phase transformation point temperature. Therefore, in order to improve the accuracy of phase transformation point temperature measurement, the formation of false phases such as "pits" and "black spots" in this type of titanium alloy should be minimized.

[0004] In the prior art, Chinese patent CN106702383A discloses a metallographic etching solution and etching method for β-titanium alloys. Specifically, the metallographic etching solution is composed of hydrofluoric acid, nitric acid, and hydrogen peroxide. This solves the technical problem that black spots and pits appearing during the etching process of β-titanium alloys due to the high Mo content, which affects the observation of the phase structure.

[0005] Chinese patent CN115342910A discloses a metallographic sample preparation method for high-strength titanium alloys. Specifically, it discloses the metallographic mounting, grinding, and polishing of the sample, as well as wiping the polished test surface with a mixed etchant. The mixed etchant comprises the following components by volume: 2 parts hydrofluoric acid, 3 parts hydrochloric acid, 5 parts nitric acid, and 190 parts water. This method solves the problem of scratches and "orange peel" phenomena occurring during the sample preparation process of near-β titanium alloys such as Ti-1500, which prevents clear display of the metallographic structure during metallographic etching. It can produce near-β titanium alloy metallographic samples with clear microstructure and no scratches.

[0006] Therefore, it is necessary to provide a etchant suitable for testing the β phase transformation point of all β-titanium alloys and near-β-titanium alloys, in order to avoid the occurrence of corrosion "pits" and "black spots" during the corrosion process, which would lead to incorrect assessment of the α phase content and affect the β phase transformation evaluation. This is of great significance. Summary of the Invention

[0007] To overcome the above technical defects, this invention provides β-type and near-β-type titanium alloy etchants, their preparation methods, and applications. These β-type and near-β-type titanium alloy etchants can reduce the occurrence of corrosion "pits" and improve the contrast of the α phase through NH4HF2, thereby enhancing the accuracy of determining the primary α phase content. Simultaneously, they improve the accuracy of evaluating the β-phase transformation point of β-titanium alloys and near-β-titanium alloys. Using these β-type and near-β-type titanium alloy β-phase transformation point etchants reduces the corrosion and operational difficulty of titanium alloy metallographic testing and improves the reproducibility of evaluation results.

[0008] The first objective of this invention is to provide β-type and near-β-type titanium alloy etchants, wherein the β-type and near-β-type titanium alloy β-phase transformation point etchants comprise agent a and agent b;

[0009] Agent a is prepared from the following raw materials in the indicated volume proportions:

[0010] 1-10 parts hydrofluoric acid, 5-10 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water;

[0011] The agent b is a 10-20 wt% NH4HF2 solution.

[0012] In one specific embodiment of the present invention, agent a is prepared from the following raw materials in parts by volume:

[0013] 2-8 parts hydrofluoric acid, 6-8 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water.

[0014] In one specific embodiment of the present invention, agent a is prepared from the following raw materials in parts by volume:

[0015] 5 parts hydrofluoric acid, 8 parts nitric acid, 11 parts hydrochloric acid, 4 parts hydrogen peroxide, and 20-80 parts water;

[0016] Agent b is a 10 wt% NH4HF2 solution.

[0017] In one specific embodiment of the present invention, agent a is prepared from the following raw materials in parts by volume:

[0018] 5 parts hydrofluoric acid, 8 parts nitric acid, 14 parts hydrochloric acid, 2 parts hydrogen peroxide, and 20-80 parts water;

[0019] Agent b is an NH4HF2 solution with a mass percentage of 20 wt%.

[0020] In one specific embodiment of the present invention, the hydrofluoric acid has a mass concentration of 40-48 wt%; the nitric acid has a mass concentration of 65.0-68.0 wt%; the hydrochloric acid has a mass concentration of 36.0-38.0 wt%; the hydrogen peroxide has a concentration of 30.0-35.0 wt%; and the NH4HF2 solution is prepared by mixing analytical grade NH4HF2 with water.

[0021] In one specific embodiment of the present invention, the hydrofluoric acid has a mass concentration of 42 wt%; the nitric acid has a mass concentration of 65.0 wt%; the hydrochloric acid has a mass concentration of 36.0 wt%; and the hydrogen peroxide has a concentration of 30.0 wt%.

[0022] The second objective of this invention is to provide a method for preparing β-type and near-β-type titanium alloy β-phase transformation pitting agents, for use in preparing the β-type and near-β-type titanium alloy β-phase transformation pitting agents of the first objective of this invention, comprising the following steps:

[0023] Based on the volume fractions of the raw materials, hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, and water are mixed to prepare agent a.

[0024] Prepare agent b by mixing NH4HF2 and water.

[0025] A third objective of this invention is to provide the application of β-type and near-β-type titanium alloy β-phase transformation point etchants in the detection of phase transformation points in near-β-type alloys or β-type titanium alloys.

[0026] In one specific embodiment of the present invention, the application involves polishing the surface of a near-β-type alloy and / or β-type titanium alloy sample, immersing the sample in agent a for etching, then removing it and immersing it in agent b for etching, and then detecting the β-phase transformation point of the sample using conventional methods.

[0027] In one specific embodiment of the present invention, the sample is immersed in agent a for 10 to 40 seconds for corrosion; the sample is immersed in agent b for 5 to 15 seconds for corrosion.

[0028] The beneficial effects of this invention are: when the β-type and near-β-type titanium alloy etchant of this invention is applied to the detection of phase transformation points of titanium alloys, it can effectively reduce the generation of corrosion bubbles or dirt spots, avoid the formation of corrosion "pits" and "black spots", reduce interference, improve the contrast of the α phase, and effectively improve the accuracy of the determination of phase transformation points of β-type and near-β-type titanium alloys. Attached Figure Description

[0029] Figure 1 The fiber structure morphology image shows the "pitted" appearance on the test surface of the TC21 sample processed using existing technology;

[0030] Figure 2 This is a partial microstructure image of the detection surface of the TC21 sample provided in Embodiment 1 of the present invention;

[0031] Figure 3 This is a partial microstructure image of the detection surface of the TC18 sample provided in Embodiment 2 of the present invention;

[0032] Figure 4 This is a partial microstructure image of the detection surface of the TC18 sample provided in Embodiment 2 of the present invention;

[0033] Figure 5 This is a partial microstructure image of the detection surface of the Ti17 sample provided in Embodiment 3 of the present invention;

[0034] Figure 6 This is a partial microstructure image of the detection surface of the Ti17 sample provided in Embodiment 3 of the present invention;

[0035] Figure 7 This is a partial microstructure image of the detection surface of the TC21 sample provided in Comparative Example 1 of the present invention.

[0036] Figure 8 This is a partial microstructure image of the detection surface of the TC21 sample provided in Comparative Example 2 of the present invention.

[0037] Figure 9 This is a partial microstructure image of the detection surface of the TC21 sample provided in Comparative Example 3 of the present invention.

[0038] Figure 10 This is a partial microstructure image of the detection surface of the TC21 sample provided in Comparative Example 4 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] This invention provides β-type and near-β-type titanium alloy β-phase transformation pitting corrosion agents, wherein the β-type and near-β-type titanium alloy β-phase transformation pitting corrosion agents include agent a and agent b;

[0041] Agent a is prepared from the following raw materials in the indicated volume proportions:

[0042] 1-10 parts hydrofluoric acid, 5-10 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water;

[0043] The agent b is an NH4HF2 solution with a mass percentage of 10-20 wt%.

[0044] In some instances, agent a is prepared from the following parts by volume of raw materials:

[0045] 2-8 parts hydrofluoric acid, 6-8 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water.

[0046] In some instances, agent a is prepared from the following parts by volume of raw materials:

[0047] 5 parts hydrofluoric acid, 8 parts nitric acid, 11 parts hydrochloric acid, 4 parts hydrogen peroxide, and 20-80 parts water;

[0048] Agent b is a 10 wt% NH4HF2 solution.

[0049] In some instances, agent a is prepared from the following parts by volume of raw materials:

[0050] 5 parts hydrofluoric acid, 8 parts nitric acid, 14 parts hydrochloric acid, 2 parts hydrogen peroxide, and 20-80 parts water;

[0051] Agent b is an NH4HF2 solution with a mass percentage of 20 wt%.

[0052] In some examples, the hydrofluoric acid has a mass concentration of 40–48 wt%; the nitric acid has a mass concentration of 65.0–68.0 wt%; the hydrochloric acid has a mass concentration of 36.0–38.0 wt%; the hydrogen peroxide has a concentration of 30.0–35.0 wt%; and the NH4HF2 solution is prepared using analytical grade NH4HF2 and water.

[0053] In some examples, the hydrofluoric acid has a mass concentration of 42 wt%; the nitric acid has a mass concentration of 65.0 wt%; the hydrochloric acid has a mass concentration of 36.0 wt%; and the hydrogen peroxide has a concentration of 30.0 wt%.

[0054] This invention also provides a method for preparing the above-mentioned β-type and near-β-type titanium alloy β-phase transformation pitting corrosion inhibitors, comprising the following steps:

[0055] Based on the volume fractions of the raw materials, hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, and water are mixed to prepare agent a.

[0056] Prepare agent b by mixing NH4HF2 and water.

[0057] This invention also provides the application of the above-mentioned β-type and near-β-type titanium alloy β-phase transformation point etchants in the detection of phase transformation points of near-β-type alloys or β-type titanium alloys.

[0058] In some instances, the application involves polishing the surface of near-β-type alloy and / or β-type titanium alloy samples, immersing the samples in agent a for etching, then removing them and immersing them in agent b for etching, and then detecting the β-phase transformation point of the samples using conventional methods.

[0059] In some instances, the sample is immersed in agent a for 10–40 s for corrosion; the sample is immersed in agent b for 5–15 s for corrosion.

[0060] To further demonstrate the effectiveness of the β-type and near-β-type titanium alloy β-phase transformation point etchants of the present invention in improving the detection of β-phase transformation points in titanium alloys, the following examples and comparative examples are provided:

[0061] Example 1

[0062] This embodiment provides a β-type and near-β-type titanium alloy β-phase transformation pitting agent, which includes agent a and agent b. Agent a is composed of the following raw materials:

[0063] 3 mL of 42 wt% hydrofluoric acid, 5 mL of 65 wt% nitric acid, 10 mL of 36 wt% hydrochloric acid, 5 mL of 30 wt% hydrogen peroxide, and 77 mL of water;

[0064] Agent b is an aqueous solution of NH4HF2 with a mass percentage of 15 wt%.

[0065] Corrosion effect test: Prepare sample TC21, polish the sample, then immerse the polished sample in agent a for 30 seconds, remove it, and then immerse it in agent b for 10 seconds; rinse with running water, add alcohol and blow dry, the morphology of the β phase transition points obtained before light polishing is as follows. Figure 2 As shown.

[0066] Example 2

[0067] This embodiment provides a β-type and near-β-type titanium alloy β-phase transformation pitting agent, which includes agent a and agent b. Agent a is composed of the following raw materials:

[0068] 3 mL of 42 wt% hydrofluoric acid, 5 mL of 65 wt% nitric acid, 10 mL of 36 wt% hydrochloric acid, 5 mL of 30 wt% hydrogen peroxide, and 77 mL of water;

[0069] Agent b is an aqueous solution of NH4HF2 with a mass percentage of 15 wt%.

[0070] Corrosion effect test: Prepare TC18 sample, polish the sample, then immerse the polished sample in agent a for 30 seconds, remove it, and then immerse it in agent b for 10 seconds; rinse with running water, add alcohol and blow dry, the morphology of the β phase transition points obtained before light polishing is as follows. Figure 3-4 As shown.

[0071] Example 3

[0072] This embodiment provides a β-type and near-β-type titanium alloy β-phase transformation pitting agent, which includes agent a and agent b. Agent a is composed of the following raw materials:

[0073] 3 mL of 42 wt% hydrofluoric acid, 5 mL of 65 wt% nitric acid, 10 mL of 36 wt% hydrochloric acid, 5 mL of 30 wt% hydrogen peroxide, and 77 mL of water;

[0074] Agent B is an aqueous solution of NH4HF2 with a mass percentage of 15 wt%.

[0075] Corrosion effect test: Prepare sample M28, polish the sample, then immerse the polished sample in agent a for 30 seconds, remove it, and then immerse it in agent b for 10 seconds; rinse with running water, add alcohol and blow dry, the morphology of the β phase transition points obtained before light polishing is as follows. Figure 5-6 As shown.

[0076] Comparative Example 1

[0077] This comparative example, based on GB / T 5168-2008 "Test Method for High and Low Magnification Microstructure of α-β Titanium Alloys", provides a etchant comprising: 3.5 mL of 41 wt% chemically pure hydrofluoric acid; 11 mL of 66 wt% chemically pure nitric acid; and 85.5 mL of water.

[0078] The microstructure morphology results obtained from this comparative corrosion effect experiment are as follows: Figure 7 As shown.

[0079] Comparative Example 2

[0080] This comparative example provides an etchant based on a metallographic etching solution and etching method for β-titanium alloy disclosed in CN106702383A. The composition differs from that of Example 1 in that hydrochloric acid is not added.

[0081] The microstructure morphology results obtained from this comparative corrosion effect experiment are as follows: Figure 8 As shown.

[0082] Comparative Example 3

[0083] This comparative example provides an etchant based on a metallographic sample preparation method for high-strength titanium alloys disclosed in CN115342910A. The difference between this comparative example and Example 1 is that hydrogen peroxide is not added.

[0084] The microstructure morphology results obtained from this comparative corrosion effect experiment are as follows: Figure 9 As shown.

[0085] Comparative Example 4

[0086] The difference between this comparative example and Example 1 is that agent b is not used for immersion corrosion.

[0087] The microstructure morphology results obtained from this comparative corrosion effect experiment are as follows: Figure 10 As shown.

Claims

1. The application of β-phase transformation point etchants for β-type and near-β-type titanium alloys in the detection of β-phase transformation points in near-β-type alloys or β-type titanium alloys, characterized in that, The β-type and near-β-type titanium alloy β-phase transformation point etchant includes agent a and agent b; the application is to polish the surface of the near-β-type alloy and / or β-type titanium alloy sample, immerse the sample in agent a for 10-40 seconds for etching, then take it out and immerse it in agent b for 5-15 seconds for etching, and then detect the β-phase transformation point of the sample according to conventional methods. Wherein, agent a is prepared from the following raw materials in the indicated volume proportions: 1-10 parts hydrofluoric acid, 5-10 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water; Agent b is an NH4HF2 solution with a mass percentage of 10-20 wt%.

2. The application according to claim 1, characterized in that, Agent a is prepared from the following raw materials in the indicated volume proportions: 2-8 parts hydrofluoric acid, 6-8 parts nitric acid, 10-15 parts hydrochloric acid, 1-5 parts hydrogen peroxide, and 20-80 parts water.

3. The application according to claim 2, characterized in that, Agent a is prepared from the following raw materials in the indicated volume proportions: 5 parts hydrofluoric acid, 8 parts nitric acid, 11 parts hydrochloric acid, 4 parts hydrogen peroxide, and 20-80 parts water; Agent b is a 10 wt% NH4HF2 solution.

4. The application according to claim 2, characterized in that, Agent a is prepared from the following raw materials in the indicated volume proportions: 5 parts hydrofluoric acid, 8 parts nitric acid, 14 parts hydrochloric acid, 2 parts hydrogen peroxide, and 20-80 parts water; Agent b is a 20 wt% NH4HF2 solution.

5. The application according to any one of claims 1-4, characterized in that: The hydrofluoric acid has a mass concentration of 40–48 wt%; the nitric acid has a mass concentration of 65.0–68.0 wt%; the hydrochloric acid has a mass concentration of 36.0–38.0 wt%; and the hydrogen peroxide has a concentration of 30.0–35.0 wt%.

6. The application according to claim 5, characterized in that: The hydrofluoric acid has a mass concentration of 42 wt%; the nitric acid has a mass concentration of 65.0 wt%; the hydrochloric acid has a mass concentration of 36.0 wt%; and the hydrogen peroxide has a concentration of 30.0 wt%.

7. The application according to claim 1, characterized in that, Based on the volume proportions of the raw materials, hydrofluoric acid, nitric acid, hydrochloric acid, hydrogen peroxide, and water are mixed to prepare agent a; Prepare agent b by mixing NH4HF2 and water.

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