Method for observing grain morphology of hard alloy tungsten carbide

Abstract

The invention discloses a hard alloy tungsten carbide grain morphology observation method, and relates to the technical field of tungsten carbide morphology observation, and the method comprises the following steps: S1, using ultrasonic waves to clean a sample to be observed; s2, carrying out first WC corrosion on the to-be-observed sample treated in the step S1; s3, carrying out cobalt phase corrosion on the to-be-observed sample treated in S2; s4, carrying out second WC corrosion on the to-be-observed sample treated in S3; and S5, carrying out electron microscope scanning on the to-be-observed sample treated in the step S4 to obtain an observation result. According to the method, the cobalt phase of the to-be-observed sample is corroded by adopting the treating fluid, the influence of the cobalt phase can be reduced, and in addition, the complete tungsten carbide morphology can be obtained after the to-be-observed sample is subjected to electron microscope scanning by combining multiple times of WC corrosion.

Description

Technical Field

[0001] The invention relates to the technical field of tungsten carbide morphology observation, and in particular to a method for observing the morphology of cemented carbide tungsten carbide grains. Background Art

[0002] The performance of cemented carbide depends on the microstructure. Understanding the microstructure is the key to controlling and improving product performance. Therefore, it is very important to observe the characteristics of the microstructure, especially the grain size and grain morphology. Analyzing the grain morphology plays a key role in the study of the mechanism of alloy preparation.

[0003] At present, the main methods for observing cemented carbide grains include sample preparation and observation. The main sample preparation includes mirror polishing and metallographic corrosion steps; the observation mainly uses a metallographic microscope and a scanning electron microscope to observe the uniformity of the alloy. Another method is to observe the uniformity of the alloy grains by observing the fracture morphology of the bending strength of the sample strip. The above two methods cannot observe the complete morphology of tungsten carbide grains due to sample polishing and fracture. In addition, electrolytic corrosion of cobalt phase is also used for observation, but it requires the addition of electrolytic equipment and the steps are cumbersome.

[0004] By observing the complete tungsten carbide grain morphology, the growth process and mechanism of tungsten carbide grains during the sintering process of cemented carbide can be analyzed and studied, which has very important guiding significance for the microstructure design and performance improvement of cemented carbide. Therefore, it needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a method for observing the morphology of cemented carbide tungsten carbide grains.

[0006] The technical solution of the present invention is as follows:

[0007] The invention discloses a method for observing the morphology of cemented carbide tungsten carbide grains. The method comprises the following steps: using a treatment liquid to remove the cobalt phase on the surface of a sample to be observed, and using a scanning electron microscope to observe the three-dimensional morphology of the WC grains of the sample to be observed.

[0008] As a preferred embodiment of the present invention, the treatment liquid is a saturated hydrochloric acid ferric chloride solution.

[0009] As a preferred embodiment of the present invention, the following steps are included:

[0010] S1: Use ultrasonic waves to clean the sample to be observed;

[0011] S2: Perform the first WC corrosion on the sample to be observed after being treated in S1;

[0012] S3: performing cobalt phase corrosion on the sample to be observed after being treated in S2;

[0013] S4: Perform a second WC corrosion on the sample to be observed after being treated in S3;

[0014] S5: Scan the sample to be observed after being processed in S4 by electron microscope to obtain the observation result.

[0015] As a preferred embodiment of the present invention, in step S2, the etching solution used in the first WC etching and / or the second WC etching is: a mixed solution of potassium hydroxide and potassium ferrocyanide in a volume ratio of 1:1.

[0016] As a preferred embodiment of the present invention, the concentration of potassium hydroxide is 10-30wt%, and the concentration of potassium ferrocyanide is 10-30wt%.

[0017] As a preferred solution of the present invention, the first WC corrosion time is 3-5 minutes.

[0018] As a preferred embodiment of the present invention, the second WC corrosion time is 20-60s.

[0019] As a preferred embodiment of the present invention, in step S3, the cobalt phase corrosion time is 10-30 minutes.

[0020] As a preferred solution of the present invention, the three-dimensional morphology of the WC grains of the observed sample is specifically: observing the three-dimensional morphology of the WC grains in a secondary electron mode using a field emission scanning electron microscope.

[0021] The beneficial effects of the present invention are:

[0022] The present invention discloses a method for observing the morphology of cemented carbide tungsten carbide grains. The method uses a treatment liquid to corrode the cobalt phase of a sample to be observed, thereby reducing the influence of the cobalt phase. In addition, multiple corrosions of WC are combined to obtain a complete tungsten carbide morphology after the sample to be observed is scanned by an electron microscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the observed morphology of the sample of Example 1;

[0024] Figure 2 This is the observed morphology of the sample of Example 2;

[0025] Figure 3 This is the observed morphology of the sample of Example 3;

[0026] Figure 4 This is the observed morphology of the sample of Comparative Example 1;

[0027] Figure 5 This is the observed morphology of the sample of Comparative Example 2. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is a method for observing the morphology of cemented carbide tungsten carbide grains. A treatment liquid is used to remove the cobalt phase on the surface of a sample to be observed, and a scanning electron microscope is used to observe the three-dimensional morphology of the WC grains of the observed sample.

[0029] Specifically, the treatment liquid is a saturated hydrochloric acid ferric chloride solution.

[0030] Further, the following steps are included:

[0031] S1: Use ultrasonic waves to clean the sample to be observed;

[0032] S2: Perform the first WC corrosion on the sample to be observed after being treated in S1;

[0033] S3: performing cobalt phase corrosion on the sample to be observed after being treated in S2;

[0034] S4: Perform a second WC corrosion on the sample to be observed after being treated in S3;

[0035] S5: Scan the sample to be observed after being processed in S4 by electron microscope to obtain the observation result.

[0036] Furthermore, in step S2, the etching solution used in the first WC etching and / or the second WC etching is: a mixed solution of potassium hydroxide and potassium ferrocyanide in a volume ratio of 1:1.

[0037] Furthermore, the concentration of potassium hydroxide is 10-30wt%, specifically 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%; the concentration of potassium ferrocyanide is 10-30wt%, specifically 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%.

[0038] Furthermore, the first WC corrosion time is 3-5 min.

[0039] Furthermore, the second WC corrosion time is 20-60s.

[0040] Further, in step S3, the cobalt phase corrosion time is 10-30min;

[0041] The present invention uses a treatment liquid to corrode the cobalt phase of the sample to be observed, which can reduce the influence of the cobalt phase. In addition, combined with multiple corrosion of WC, the complete tungsten carbide morphology can be obtained after the sample to be observed is scanned by an electron microscope.

[0042] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0043] Example 1

[0044] A method for observing the morphology of cemented carbide tungsten carbide grains, comprising the following steps:

[0045] S1: Use ultrasonic waves to clean the sample to be observed;

[0046] S2: The sample to be observed after being treated in S1 is subjected to the first WC corrosion, and the corrosion liquid is a mixture of potassium hydroxide and potassium ferrocyanide in a volume ratio of 1:1, the concentration of potassium hydroxide is 20wt%, the concentration of potassium ferrocyanide is 20wt%, and the corrosion time is 4min;

[0047] S3: performing cobalt phase corrosion on the sample to be observed after being treated in S2, specifically, using a saturated hydrochloric acid ferric chloride solution to remove the cobalt phase on the surface of the sample to be observed;

[0048] S4: performing a second WC corrosion on the sample to be observed after being treated in S3, wherein the corrosion liquid is a mixture of potassium hydroxide and potassium ferrocyanide in a volume ratio of 1:1, the concentration of potassium hydroxide is 20wt%, the concentration of potassium ferrocyanide is 20wt%, and the corrosion time is 20s;

[0049] S5: Scan the sample to be observed after S4 treatment with an electron microscope. Specifically, a field emission scanning electron microscope (SEM, JE-OL-JSM6701F, Japan) is used to observe the three-dimensional morphology of WC grains in the secondary electron mode (SEI). The equipment is equipped with an Oxford-INCA-EDX spectrometer, which can also perform composition analysis on the micro-area to obtain observation results.

[0050] The specific sample is W-6.12C-12Co, that is, the carbon content accounts for 6.12wt%. The results are shown in Figure 1 .

[0051] Example 2

[0052] The difference from Example 1 is that the sample is W-6.16C-12Co, that is, the carbon content accounts for 6.16wt%. Figure 2 .

[0053] Example 3

[0054] The difference from Example 1 is that the sample is W-6.20C-12Co, that is, the carbon content accounts for 6.20wt%. Figure 3 .

[0055] Comparative Example 1 (fracture morphology)

[0056] The sample is W-6.12C-12Co, that is, the carbon content accounts for 6.12wt%.

[0057] The observation method used is: the cobalt phase corrosion adopts the fracture of the test specimen strip of the national standard GB3851-2015 for testing the bending strength, and then observes it by scanning electron microscope. The results are shown in Figure 4 .

[0058] Comparative Example 2 (Polishing Morphology)

[0059] The sample is W-6.12C-12Co, that is, the carbon content accounts for 6.12wt%.

[0060] The observation methods used are:

[0061] S1: Mirror polishing, the specific operation is as follows: (1) Sample pre-grinding: use a 75-micron diamond magnetic grinding disc, continuously flow water for grinding, and the grinding and polishing time is 4 minutes; (2) Sample coarse grinding: use an 18-micron diamond magnetic grinding disc, continuously flow water for grinding, and the grinding and polishing time is 2-3 minutes; (3) Sample fine grinding: use a 10-micron magnetic grinding disc, continuously flow water for grinding, and the grinding and polishing time is 2-3 minutes; (4) Coarse polishing: use a nylon polishing cloth to add a 9-micron diamond suspension for automatic grinding, and the polishing time is 2-3 minutes; (5) Fine polishing: use a nylon polishing cloth to add a 3-micron diamond suspension for automatic grinding, and the polishing time is 2-3 minutes.

[0062] S2. Metallographic corrosion includes: first WC corrosion-cobalt phase corrosion-second WC corrosion.

[0063] The first WC corrosion is to immerse the polished nanocrystalline cemented carbide mirror surface into the WC corrosion solution for the first time for corrosion, and the corrosion time is 3min-3.5min; wherein the WC corrosion solution is an aqueous solution containing 20wt% potassium ferrocyanide and 20wt% potassium hydroxide.

[0064] Cobalt phase corrosion: the nanocrystalline cemented carbide polished mirror after the first WC corrosion is immersed in a cobalt phase corrosion solution for corrosion for 15s-20s; the cobalt phase corrosion solution is a ferric chloride hydrochloric acid solution, and its ratio is calculated by mass: 91.9 parts of ferric chloride and 10 parts of concentrated hydrochloric acid are dissolved in 100 parts of distilled water.

[0065] WC etching again: the polished mirror surface of the nanocrystalline cemented carbide after the cobalt phase etching is immersed in WC etching solution again for etching for 8 seconds; wherein the WC etching solution is an aqueous solution containing 20wt% potassium ferrocyanide and 20wt% potassium hydroxide.

[0066] The samples were observed using a field emission scanning electron microscope. Figure 5 .

[0067] From the results, it can be seen that Examples 1-3 can obtain the complete three-dimensional morphology of WC, while Comparative Examples 1 and 2 cannot observe the complete tungsten carbide grain morphology. Therefore, it can be seen that the observation method of the present invention is simple and feasible.

[0068] The above-mentioned embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for observing the grain morphology of cemented carbide tungsten carbide, characterized in that: The cobalt phase on the surface of the sample to be observed was removed by using a treatment liquid, and the three-dimensional morphology of the WC grains of the sample to be observed was observed by using a scanning electron microscope.

2. The method for observing the grain morphology of cemented carbide tungsten carbide according to claim 1, characterized in that: The treatment liquid is a saturated hydrochloric acid ferric chloride solution.

3. The method for observing the grain morphology of cemented carbide tungsten carbide according to claim 1, characterized in that: The following steps are involved: S1: Use ultrasonic waves to clean the sample to be observed; S2: Perform the first WC corrosion on the sample to be observed after being treated in S1; S3: performing cobalt phase corrosion on the sample to be observed after being treated in S2; S4: Perform a second WC corrosion on the sample to be observed after being treated in S3; S5: Scan the sample to be observed after being processed in S4 by electron microscope to obtain the observation result.

4. The method for observing the grain morphology of cemented tungsten carbide according to claim 3, characterized in that: In step S2, the etching solution used in the first WC etching and / or the second WC etching is: a mixed solution of potassium hydroxide and potassium ferrocyanide in a volume ratio of 1:

1.

5. The method for observing the grain morphology of cemented tungsten carbide according to claim 4, characterized in that: The concentration of potassium hydroxide is 10-30 wt %, and the concentration of potassium ferrocyanide is 10-30 wt %.

6. The method for observing the grain morphology of cemented carbide tungsten carbide according to claim 3, characterized in that: The first WC corrosion time is 3-5min.

7. The method for observing the grain morphology of cemented carbide tungsten carbide according to claim 3, characterized in that: The second WC corrosion time is 20-60s.

8. The method for observing the grain morphology of cemented tungsten carbide according to claim 3, characterized in that: In step S3, the cobalt phase corrosion time is 10-30 minutes.

9. The method for observing the grain morphology of cemented tungsten carbide according to claim 1, characterized in that: The three-dimensional morphology of the WC grains of the observed sample is specifically: observing the three-dimensional morphology of the WC grains in a secondary electron mode using a field emission scanning electron microscope.

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