阅读说明：本技术 一种硬质合金中钴相xrd分析用样品的制备方法 (Preparation method of sample for cobalt phase XRD analysis in hard alloy ) 是由 王书明 曹瑞军 赵敏丹 于 2019-09-19 设计创作，主要内容包括：本发明涉及一种硬质合金中钴相XRD分析用样品的制备方法,属于XRD样品制备技术领域。切取硬质合金的待测样品,依次采用由粗到细的4道砂纸对待测面进行磨光处理,每道砂纸磨至样品表面划痕均匀且处于一个方向时,更换下一道砂纸,同时,将试样旋转90°,继续打磨；最后用无水乙醇清洗；将磨好的样品连接电源正极,铜板连接负极,置于电解液中进行电解,电解液包括氢氧化钠、酒石酸钠、柠檬酸钠、高氯酸和去离子水等；将样品取出,依次用稀盐酸和去离子超声清洗。本发明采用选择性电解侵蚀,去除WC相,保留Co相,可以很好地对Co的晶体结构进行解析,同时本方法操作简便。(The invention relates to a preparation method of a sample for cobalt phase XRD analysis in hard alloy, belonging to the technical field of XRD sample preparation. Cutting a hard alloy sample to be tested, sequentially polishing the surface to be tested by adopting 4 abrasive papers from coarse to fine, replacing the next abrasive paper when each abrasive paper is ground until the scratches on the surface of the sample are uniform and are in one direction, and simultaneously rotating the sample by 90 degrees for continuous polishing; finally, washing with absolute ethyl alcohol; connecting the ground sample with a positive electrode of a power supply, connecting a copper plate with a negative electrode, and placing the sample in an electrolyte for electrolysis, wherein the electrolyte comprises sodium hydroxide, sodium tartrate, sodium citrate, perchloric acid, deionized water and the like; the sample was taken out and washed with dilute hydrochloric acid and deionized ultrasound in sequence. The method adopts selective electrolytic erosion to remove the WC phase and reserve the Co phase, can well analyze the crystal structure of Co, and is simple and convenient to operate.)

1. A preparation method of a sample for XRD analysis of cobalt phase in hard alloy comprises the following steps:

(1) preparing an electrolyte: the electrolyte comprises sodium hydroxide, sodium tartrate, sodium citrate and deionized water, wherein each 100mL of the deionized water contains 15-20 g of the sodium hydroxide, 2-5 g of the sodium tartrate and 1-2 g of the sodium citrate;

(2) cutting a hard alloy sample to be tested, sequentially polishing the surface to be tested by adopting 4 abrasive papers from coarse to fine, replacing the next abrasive paper when each abrasive paper is ground until the scratches on the surface of the sample are uniform and are in one direction, and simultaneously rotating the sample by 90 degrees for continuous polishing; finally, washing with absolute ethyl alcohol;

(3) connecting the ground sample with a positive electrode of a power supply, connecting a copper plate with a negative electrode, placing the sample in an electrolyte, electrolyzing for 40-60 minutes at an electrolytic voltage of 7-10V and a current of 0.5-1A;

(4) taking out the sample, washing with water, and then placing the sample in dilute hydrochloric acid for ultrasonic cleaning for 20-40 seconds;

(5) and (4) placing the mixture into deionized water, carrying out ultrasonic cleaning for 20-40 seconds, and finally drying the mixture by using a blower.

2. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 1, wherein: the electrolyte also contains perchloric acid, and each 100mL of deionized water contains 1-2 mL of perchloric acid.

3. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 1, wherein: and sequentially polishing the surface to be measured by using 150#, 500#, 1200# and 2500# sandpaper.

4. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 3, wherein: when the sample is prepared, a polishing process is added after the polishing treatment.

5. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 1, wherein: during electrolysis, the temperature of the electrolyte is controlled to be 25-50 ℃.

6. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 5, wherein: a water bath was used to control the temperature of the electrolyte.

7. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 1, wherein: when the hard alloy sample is connected with a power supply, the power line connector is arranged outside the electrolyte.

8. The method for preparing a sample for XRD analysis of cobalt phase in cemented carbide according to claim 1, wherein: the concentration of the dilute hydrochloric acid is 1-5 vol.%.

Technical Field

The invention relates to a preparation method of a sample for cobalt phase XRD analysis in hard alloy, belonging to the technical field of XRD sample preparation.

Background

The hard alloy has higher hardness and wear resistance, mainly consists of WC and a small amount of Co, wherein the WC is used as a main phase and has high hardness and thermal stability, but the hard alloy is difficult to sinter and form among particles, so that the hard alloy is added with the Co as a binder phase and is sintered and formed. W has certain solid solubility in Co crystal lattice, on one hand, the higher the initial temperature is, the larger the solid solubility of W is; on the other hand, as the temperature decreases, the solid solubility gradually decreases, and therefore both the sintering temperature and the cooling rate affect the solid solubility of the final Co phase.

The solid solution of W changes the mechanical property of Co and influences the hardness and thermal stability of the final alloy. On the other hand, the solid solution of W reduces the thermodynamic stability of the high-temperature Co phase FCC (face-centered cubic), raises the solid phase transformation point of Co to 730 ℃, and the high-temperature phase is transformed into a HCP hexagonal close-packed low-temperature phase and is kept at room temperature. However, W is a substitutional solid solution in FCC and a gap solid solution in HCP, resulting in a decrease in the free energy difference between the two, a decrease in the low-temperature non-diffusive phase transition point, and a decrease in the amount of FCC to HCP transition at low temperature.

It can be seen that the solid solution of W affects the properties and solid state transition of Co, resulting in more complex effects. The analysis of the Co phase crystal structure is the key to research the relation between the performance of the hard alloy and the microstructure. However, the proportion of Co in cemented carbide is small, and is at most 6% or less, and in X-ray diffraction analysis, the strongest diffraction peak is eliminated and the rest is buried in the background, and it is difficult to conduct correlation studies.

Disclosure of Invention

The invention provides a preparation method of a sample for XRD analysis of a Co binding phase in hard alloy, aiming at the problems that the proportion of Co in the hard alloy is small and X-ray diffraction analysis is difficult.

A preparation method of a sample for XRD analysis of a cobalt phase (binding phase) in hard alloy comprises the following steps:

(1) preparing an electrolyte: the electrolyte comprises sodium hydroxide, sodium tartrate, sodium citrate and deionized water, wherein 15-20 g of sodium hydroxide, 2-5 g of sodium tartrate and 1-2 g of sodium citrate are added into every 100mL of deionized water; according to the specific characteristics of the hard alloy, perchloric acid can be added, and 1-2 mL of perchloric acid is added into every 100mL of deionized water;

(2) cutting a hard alloy sample to be tested, sequentially polishing the surface to be tested by adopting 4 abrasive papers from coarse to fine, replacing the next abrasive paper when each abrasive paper is ground until the scratches on the surface of the sample are uniform and are in one direction, and simultaneously rotating the sample by 90 degrees for continuous polishing; finally, washing with absolute ethyl alcohol;

(3) connecting the ground sample with a positive electrode of a power supply, connecting a pure copper plate with a negative electrode, placing the sample in an electrolyte, electrolyzing for 40-60 minutes at an electrolytic voltage of 7-10V and a current of 0.5-1A;

(4) taking out the sample, washing with water, and then placing the sample in dilute hydrochloric acid for ultrasonic cleaning for 20-40 seconds;

(5) and (4) placing the mixture into deionized water, carrying out ultrasonic cleaning for 20-40 seconds, and finally drying the mixture by using a blower.

In the step (2), the surface to be measured is polished by sequentially adopting 150#, 500#, 1200#, 2500# sandpaper; when the sample is prepared, the polishing process can be added after the polishing treatment according to the surface quality requirement.

In the step (3), during electrolysis, the temperature of the electrolyte is controlled to be 25-50 ℃, and if the temperature rise of the electrolyte is too high, a water bath can be added to control the temperature of the electrolyte.

In the step (3), when the hard alloy sample is connected with the power supply, the power line connector is arranged outside the electrolyte and cannot be submerged in the electrolyte.

In the step (4), the concentration of the dilute hydrochloric acid is 1-5 vol.%.

Has the advantages that:

1. in the invention, sodium tartrate and sodium citrate are added into the electrolyte, which is helpful for complexing OH^-And the local electrolysis speed of the hard alloy is alleviated, and a small amount of perchloric acid is beneficial to improving the interface corrosion capability of tungsten carbide and Co.

2. According to the invention, an electrolytic voltage of 7-10 v is adopted, so that the tungsten carbide can be quickly and selectively corroded, and the damage of Co can be reduced.

3. The invention adopts dilute hydrochloric acid ultrasonic cleaning, which is beneficial to fully cleaning the electrolyte and the electrolytic product residue and avoiding the influence of the electrolyte on the detection result.

The method adopts selective electrolytic erosion to remove the WC phase and reserve the Co phase, can well analyze the crystal structure of Co, and is simple and convenient to operate.

Drawings

FIG. 1 is a schematic view of an experimental apparatus according to the present invention.

FIG. 2 is an XRD pattern of selective erosion of cemented carbide according to the invention over time.

3-1 through 3-3 are the micro-features of the selectively eroded cemented carbide of examples 1-3 of the present invention.

Description of the main reference numerals:

1 hard alloy test bar 2 copper plate

3 electrolyte 4 insulation heat shrinkable tube

5 D.C. regulated power supply

Detailed Description

The method comprises the steps of firstly cutting a hard alloy sample, sequentially polishing a surface to be measured by 150#, 500#, 1200#, 2500# abrasive paper, then preparing electrolytes such as sodium hydroxide and sodium tartrate according to a certain proportion, electrolyzing for 40-60 minutes by taking the hard alloy as a positive electrode and a copper plate as a negative electrode and under the electrolytic voltage of 7-10V, and finally sequentially cleaning by dilute hydrochloric acid and deionized ultrasonic.

The method for preparing the sample for XRD analysis of the binding phase in the hard alloy comprises the following specific steps:

(1) preparing an electrolyte: per 100mL deionized water, sodium hydroxide: 15-20 g, sodium tartrate: 2-5 g of electrolyte, 1-2 g of sodium citrate and 1-2 mL of perchloric acid. Depending on the specific properties of the cemented carbide, perchloric acid may not be added.

(2) Preparing a sample: cutting a proper amount of hard alloy, sequentially grinding the surface to be measured by adopting 150#, 500#, 1200#, 2500# abrasive paper, changing the next piece of abrasive paper when each piece of abrasive paper is ground until scratches on the surface of the sample are uniform and are positioned in one direction, and simultaneously rotating the sample by 90 degrees and continuously grinding. And finally, washing with absolute ethyl alcohol. When the sample is prepared, the polishing process can be added according to the surface quality requirement.

(3) Electrolysis: as shown in figure 1, the electrolysis experimental device adopted by the invention comprises an electrolytic bath and a direct current stabilized voltage power supply 5, wherein an electrolyte 3 is arranged in the electrolytic bath, during electrolysis, a hard alloy test bar 1 is used as a positive electrode and is arranged in the electrolyte 3 at the upper part of the electrolytic bath, a copper plate 2 is used as a negative electrode and is arranged in the electrolyte 3 at the lower part of the electrolytic bath, and a lead connected with the copper plate is separated from the electrolyte 3 by an insulated heat shrinkable tube 4.

And connecting the ground sample with the positive electrode of a power supply, connecting the pure copper plate with the negative electrode, and placing the sample in an electrolyte with the electrolytic voltage of 7-10V and the current of 0.5-1A. Electrolyzing for 40-60 minutes. During electrolysis, the temperature of the electrolyte is controlled to be 25-50 ℃, and if the temperature rise of the electrolyte is too high, a water bath can be increased. When the hard alloy sample is connected with a power supply, the power line connector is not submerged in the electrolyte.

(4) Cleaning: and turning off a power supply, taking out the sample, washing with water, then placing the sample in 1-5% dilute hydrochloric acid, and carrying out ultrasonic cleaning for 20-40 seconds. And then placing the mixture in deionized water, performing ultrasonic treatment for 20-40 seconds, and finally drying the mixture by using a blower.

Example 1

Firstly, cutting a hard alloy sample (the cobalt content is 6 wt%), polishing a surface to be detected, then preparing electrolyte, carrying out selective electrolytic corrosion, and finally cleaning. The method comprises the following specific steps:

step one, preparing electrolyte and deionized water: 100mL, sodium hydroxide: 15g, sodium tartrate: 2g, 1g of sodium citrate and 1mL of perchloric acid.

And step two, cutting a sintered hard alloy test bar with the diameter of 5mm and the length of 15 mm.

And step three, sequentially grinding the opposite end faces by using 150#, 500#, 1200#, 2500# sandpaper, and polishing on a polishing machine, wherein the polishing paste is W2.5 diamond polishing paste.

And step four, connecting the sample with a positive electrode of a power supply, connecting a pure copper plate with a negative electrode, and placing the sample in an electrolyte with the electrolytic voltage of 10V. The temperature of the electrolyte is controlled at 25 ℃, and if the temperature rise of the electrolyte is too large, the temperature rise of the electrolyte can be controlled by adopting a water bath. The electrolysis was carried out for 20 minutes, 40 minutes and 60 minutes, respectively, and XRD analysis was carried out for the difference in electrolysis time and the degree of WC phase exfoliation.

And step five, taking out the sample, washing the sample by using water, and then placing the sample in 2 vol.% diluted hydrochloric acid for ultrasonic washing for 20 seconds. And the deionized water is replaced, the ultrasonic treatment is carried out for 20 seconds again, and finally the drying is carried out by a blower.

Example 2

Firstly, cutting a hard alloy sample (the cobalt content is 10 wt%), polishing a surface to be detected, then preparing electrolyte, carrying out selective electrolytic corrosion, and finally cleaning. The method comprises the following specific steps:

step one, preparing electrolyte and deionized water: 100mL, sodium hydroxide: 18g, sodium tartrate: 3g, sodium citrate 1.5g and perchloric acid 1.5 mL.

And step two, cutting a sintered hard alloy test bar with the diameter of 5mm and the length of 15 mm.

And step three, sequentially grinding the opposite end faces by using 150#, 500#, 1200#, 2500# sandpaper, and polishing on a polishing machine, wherein the polishing paste is W2.5 diamond polishing paste.

And step four, connecting the sample with a positive electrode of a power supply, connecting a pure copper plate with a negative electrode, and placing the sample in an electrolyte with an electrolytic voltage of 9V. And electrolyzing for 50 minutes. The temperature of the electrolyte is controlled at 30 ℃, and if the temperature rise of the electrolyte is too large, the temperature rise of the electrolyte can be controlled by adopting a water bath.

And step five, taking out the sample, washing the sample by using water, and then placing the sample in 5 vol.% dilute hydrochloric acid for ultrasonic washing for 40 seconds. And the deionized water is replaced, the ultrasonic treatment is carried out for 20 seconds again, and finally the drying is carried out by a blower.

Example 3

The preparation method of the sample for XRD analysis of the binding phase in the hard alloy (the cobalt content is 12wt percent) comprises the following specific steps:

step one, preparing electrolyte and deionized water: 100mL, sodium hydroxide: 20g, sodium tartrate: 5g, 2g of sodium citrate and 2mL of perchloric acid.

And step two, cutting three sintered hard alloy test bars with the diameter of 5mm and the length of 15 mm.

And step three, sequentially grinding the opposite end faces by using 150#, 500#, 1200#, 2500# sandpaper, and polishing on a polishing machine, wherein the polishing paste is W2.5 diamond polishing paste.

And step four, connecting the sample with a positive electrode of a power supply, connecting a pure copper plate with a negative electrode, placing the sample in an electrolyte, and electrolyzing for 40 minutes at an electrolytic voltage of 8V. The temperature of the electrolyte is controlled at 35 ℃, and if the temperature rise of the electrolyte is too large, the temperature rise of the electrolyte can be controlled by adopting a water bath.

Step five, the sample is taken out, washed with water, then placed in 1 vol.% dilute hydrochloric acid and ultrasonically washed for 30 seconds. And the deionized water is replaced, the ultrasonic treatment is carried out for 30 seconds again, and finally the drying is carried out by a blower.

The samples prepared in examples 1-3 were subjected to microscopic morphology and XRD analysis:

1) the obtained samples are respectively placed on an XRD diffractometer for scanning, as shown in figure 2, XRD scanning results of the hard alloy sample in the example 1 are XRD scanning results of an untreated sample, a sample after being electrolyzed for 20 minutes, 40 minutes and 60 minutes, and XRD scanning results of the sample after being treated are sequentially from top to bottom, and as can be seen from figure 3, by adopting the method, the diffraction peak of the tungsten carbide is gradually weakened and the cobalt peak is gradually strengthened along with the increase of the electrolysis time, which shows that the method can effectively remove the tungsten carbide after being electrolyzed for 40-60 minutes, and is beneficial to the analysis of the crystal structure of the cobalt.

2) The samples obtained in examples 1 to 3 were analyzed by scanning electron microscopy, and as shown in FIGS. 3-1 to 3-3, it can be seen that the WC hard phase was removed well in each example by electrolysis for not less than 40 minutes.

The above embodiments are only used for illustrating but not limiting the technical solutions of the present invention, and although the above embodiments describe the present invention in detail, those skilled in the art should understand that: modifications and equivalents may be made thereto without departing from the spirit and scope of the invention and any modifications and equivalents may fall within the scope of the claims.