CN106319260B - A kind of high-melting-point high-entropy alloy and its coating production - Google Patents

Abstract

The invention relates to the technical field of new alloy materials, and provides a high-melting-point high-entropy alloy composed of CoCrMoNbTi; the atomic molar ratio of the above components is: (0.8~1.1):(0.8~1.1):(0.8~1.1): (0.8~1.1):(0~1.1); the purity of selected Co, Cr, Mo, Nb and Ti raw materials is not less than 99%; also provides a kind of above alloy bulk material and laser cladding coating method of preparation. The beneficial effects of the invention are: the high-entropy alloy has a simple body-centered cubic structure, has high strength and thermal stability, and has excellent mechanical properties, and can meet the higher performance requirements of materials in modern industry, especially high temperature Performance requirements; the preparation of the high-entropy alloy coating promotes and expands the application field of the high-entropy alloy; the preparation method is simple, easy to implement, and has broad application prospects.

Description

A kind of high melting point high entropy alloy and its coating preparation method

technical field

The invention relates to the technical field of alloy materials, in particular to a high-melting-point high-entropy alloy and a coating preparation method thereof.

Background technique

The concept of high-entropy alloys has opened up a new way for the research of alloy materials. High-entropy alloys generally contain 5 or more components, and the atomic ratio of each element is between 5% and 35%. Due to the high entropy effect, multi-element alloys with equiatomic or near-atomic molar ratios do not form brittle intermetallic compound phases with complex structures, but instead form simple solid solution structures, endowing the alloys with excellent comprehensive properties. Especially in recent years, the high-melting-point high-entropy alloys designed and developed through the organic combination of several high-melting-point alloys have significantly improved the relevant high-temperature properties compared with traditional high-temperature alloys, and have broad application prospects, becoming one of the hot branches of high-entropy alloy research.

CN201510010329.0 discloses a method for adjusting and controlling the structure of AlCoCrFeNi high-entropy alloy. In the atmospheric environment, the AlCoCrFeNi high-entropy alloy is coated with a coating agent, and the structure is changed by deep supercooling and rapid solidification. The large undercooling degree of entropy alloy can control the microstructure.

CN201310161152.5 discloses a method for preparing a high-entropy alloy coating containing amorphous nanocrystals, which can be used to prepare high-entropy alloy coatings and bulk materials with superior comprehensive performance.

CN200810063807.4 discloses a high-entropy alloy-based composite material and a preparation method thereof. The properties such as hardness and strength of the composite material are significantly improved compared with those before the composite material.

None of the above materials involve high melting point high entropy alloys and their preparation.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a high-melting-point high-entropy alloy, to design and develop a high-melting-point high-entropy alloy of the CoCrMoNbTi system by using vacuum arc melting technology, to determine the composition range and melting process of the alloy, to test The microstructure and related properties of the alloy. At the same time, a high-melting-point high-entropy alloy coating was prepared by laser cladding technology and thermal spraying technology, and the coating preparation process and related microstructure properties were determined, paving the way for practical applications.

A high-melting-point high-entropy alloy of the present invention is composed of CoCrMoNbTi; the atomic molar ratio of the above components is: Co:Cr:Mo:Nb:Ti=(0.8～1.1):(0.8～1.1):(0.8～1.1) :(0.8～1.1):(0～1.1).

Further, when preparing the high-melting-point high-entropy alloy, the purity of the selected Co, Cr, Mo, Nb and Ti raw materials is 99%-99.99%.

The present invention also provides a method for preparing the above-mentioned high-melting-point high-entropy alloy bulk material, comprising the following steps:

Step 1. Surface purification of Co, Cr, Mo, Nb, Ti raw materials to remove oxides;

Step 2, Co, Cr, Mo, Nb, Ti are weighed according to the molar ratio (0.8～1.1):(0.8～1.1):(0.8～1.1):(0.8～1.1):(0～1.1);

Step 3. Put the configured raw materials in the water-cooled copper mold in the vacuum non-consumable tungsten arc melting furnace, vacuumize the electric arc furnace, and the air pressure in the electric arc furnace is 0~6×10 ^-3 Pa; Argon enters the induction cooker, and the pressure reaches 0.4 to 0.6 atmospheres;

Step 4. During the smelting process, each time the alloy is melted, the arc is kept for 30-60s. After the alloy block is cooled, it is turned over, and this is repeated 3 to 5 times or more; after the alloy is evenly smelted, take it out to obtain the high melting point High entropy alloys.

The present invention also provides a method for preparing the above-mentioned high-melting-point high-entropy alloy laser cladding coating, comprising the following steps:

Step 1. Mix the powder of the high-melting-point high-entropy alloy in an omnidirectional planetary ball mill, the ball milling speed is 140-160r/min, and the time is 14-16h, and place the uniformly mixed powder on the carbon steel substrate , the preset thickness is 600-800um;

Step 2. Use high-power laser for multi-channel cladding. The laser power is 2.3-2.7kW, the scanning speed is 300-600mm/min, the spot diameter is 3-4mm, and the overlap rate is 25%-40%. Protect with inert gas.

Further, the rotational speed of the ball mill in step 1 is 150r/min, and the preset thickness of the alloy powder is 700um.

Further, the inert gas in step 2 is Ar.

The beneficial effects of the invention are: the high-entropy alloy has a simple body-centered cubic structure, has high strength and thermal stability, and has excellent mechanical properties, and can meet the higher performance requirements of materials in modern industry, especially high temperature Performance requirements; the preparation of the high-entropy alloy coating promotes and expands the application field of the high-entropy alloy; the preparation method is simple, easy to implement, and has broad application prospects.

Description of drawings

FIG. 1 shows the X-ray diffraction pattern of the CoCrMoNbTi high-entropy alloy in Example 1 of the present invention.

FIG. 2 is a scanning electron microscope backscattered photograph of the CoCrMoNbTi high-entropy alloy in Example 1.

FIG. 3 is a scanning electron microscope backscattered photograph of the CoCrMoNbTi high-entropy alloy coating interface in Example 2.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be regarded as isolated, and they can be combined with each other to achieve better technical effects. In the drawings of the following embodiments, the same reference numerals appearing in each drawing represent the same features or components, which can be applied in different embodiments.

An embodiment of the present invention is a high-melting-point high-entropy alloy, the high-melting-point high-entropy alloy is composed of CoCrMoNbTi; the atomic molar ratio of the above components is: (0.8-1.1): (0.8-1.1): (0.8-1.1) :(0.8-1.1):(0-1.1).

When preparing the high-melting-point high-entropy alloy, the purity of the selected Co, Cr, Mo, Nb and Ti raw materials is not less than 99%, preferably 99%-99.99%.

A method for preparing the above-mentioned high-melting-point high-entropy alloy bulk material, comprising the steps of:

Step 1. Surface purification of Co, Cr, Mo, Nb, Ti raw materials to remove oxides;

Step 2, Co, Cr, Mo, Nb, Ti are weighed according to the molar ratio (0.8～1.1):(0.8～1.1):(0.8～1.1):(0.8～1.1):(0～1.1);

Step 3. Put the configured raw materials in the water-cooled copper mold in the vacuum non-consumable tungsten arc melting furnace, vacuumize the electric arc furnace, and the air pressure in the electric arc furnace is 0~6×10 ^-3 Pa; Argon enters the induction cooker, and the pressure reaches 0.4 to 0.6 atmospheres;

Step 4. During the smelting process, each time the alloy is melted, the arc is kept for 30-60s. After the alloy block is cooled, it is turned over, and this is repeated 3 to 5 times or more; after the alloy is evenly smelted, take it out to obtain the high melting point High entropy alloys.

A method for preparing the above-mentioned high-melting-point high-entropy alloy laser cladding coating, comprising the steps of:

Step 1. Mix the powder of the high-melting-point high-entropy alloy in an omnidirectional planetary ball mill, the ball milling speed is 140-160r/min, and the time is 14-16h, and place the uniformly mixed powder on the carbon steel substrate , the preset thickness is 600-800um;

Step 2. Use high-power laser for multi-channel cladding. The laser power is 2.3-2.7kW, the scanning speed is 300-600mm/min, the spot diameter is 3-4mm, and the overlap rate is 25%-40%. Protect with inert gas.

Preferably, the ball milling speed in step 1 is 150r/min, and the preset thickness of the alloy powder is 700um; the inert gas in step 2 is Ar.

Example 1

The preparation process of the high-melting-point high-entropy alloy in this embodiment is as follows:

Raw material preparation: Co, Cr, Mo, Nb and Ti block raw materials are mechanically removed from scale, and accurately weighed according to the molar ratio Co:Cr:Mo:Nb:Ti=1:1:1:1:1:0.4 Proportioning, cleaning with ultrasonic vibration in alcohol;

Alloy smelting: use vacuum non-consumable electric arc furnace to smelt alloy; put the mixed raw materials in the water-cooled copper mold in the vacuum arc melting furnace, and vacuum the electric arc furnace. When the vacuum degree reaches 5×10-3Pa, charge Enter industrial argon until the pressure in the furnace reaches half an atmospheric pressure; each time the alloy is melted, the arc is kept for 45s; after the alloy is cooled, turn the alloy in the crucible to continue melting, and repeat this 4 times to ensure that the alloy is mixed evenly .

The structure and properties of the alloy are analyzed as follows:

X-ray diffraction (XRD) results: After cutting the sample into 10×10×10mm squares by wire cutting, the surface of the sample was sequentially treated with metallographic Sandpaper carefully. The X-ray diffractometer is used to analyze the phase composition of the metallographic sample, the scanning step is 0.01/s, and the scanning angle 2θ ranges from 10° to 90°. The test results are shown in Figure 1.

Scanning electron microscope (SEM) results: After the sample was cut into 10×10×10mm squares by wire cutting, it was carefully ground with metallographic sandpaper of 150#, 400#, 800#, 1200#, 1500# and 2000#, and mechanically After polishing, the alloy structure was observed using the backscattering mode of the scanning electron microscope. The test results are shown in Figure 2.

Microstructure analysis found that the alloy is composed of a simple BCC solid solution, as shown in Figure 1; the alloy structure is composed of typical dendrites and interdendritic structures, as shown in Figure 2. It can be seen that the alloy microstructure is a typical high-entropy alloy microstructure.

Microhardness: Use 401MVD digital micro Vickers hardness tester to measure the microhardness of the alloy. Before the hardness test, the alloy samples are made of 150#, 400#, 800#, 1200#, 1500# and 2000# gold Carefully ground with sandpaper and mechanically polished. The load loaded during the test is 500g and kept for 15s. 7 points were randomly tested for each sample. After removing the largest and smallest data, the average value of the remaining 5 data points was taken as the microhardness value of the alloy, as shown in Table 1.

The microhardness of the high-melting-point high-entropy alloy in Table 1 Example 1

MTS 809 material testing machine was used to test the mechanical properties of the alloy at room temperature. The sample size was φ3mm×6mm, and the strain rate was 1×10 ^-4 s ^-1 . The alloy had a very high fracture strength, up to 1780MPa; for brittle fracture. The thermal compression test is carried out on a Gleeble-1500 thermal simulation testing machine, the deformation temperature is 600-1300°C, the strain rate is 0.001-0.1s ^-1 , and the deformation is 30%-60%. The sample is heated to the preset temperature at a speed of 8-12°C/s and then compressed. Under high-temperature compression at 1200°C, the compressive strength of the alloy is as high as 680MPa, and the compression plastic deformation is greater than 35%, which has excellent high-temperature strength and high temperature plastic deformation capacity.

Example 2

The preparation of the high melting point high entropy alloy laser cladding coating in this embodiment is as follows:

Raw material preparation: put Co powder, Cr powder, Mo powder, Nb powder and Ti powder into the composition ratio according to the molar ratio of Example 1, use an electronic balance to weigh the powders of various elements, and place the configured powders in an all-round Mix in a planetary ball mill, set the speed at 150r/min, and take 15h to obtain a uniformly mixed powder;

Substrate treatment: smooth the surface of the 45 steel substrate with sandpaper, then wash the polished substrate once with absolute ethanol and acetone, and finally perform sandblasting to obtain a roughened substrate;

Coating preparation: Place the mixed powder obtained in step 1 on a 45mm rigid substrate to obtain a preset powder layer with a thickness of about 700um, and use a laser for multi-pass cladding with a laser power of 2.3-2.7kW and a scanning speed of 300 ～600mm/min, the spot diameter is 3～4mm, and the inert gas Ar gas is used for protection during cladding. The invention adopts laser cladding technology to prepare a high-entropy alloy coating with excellent comprehensive performance on the roughened substrate surface.

Microstructure and performance analysis of high-entropy alloy laser cladding coating:

X-ray diffraction (XRD) results: After cutting the coating sample into 10×10×10mm squares by wire cutting, use 150#, 400#, 800#, 1200#, 1500# and 2000# in turn on the coating surface Grind carefully with metallographic sandpaper. The X-ray diffractometer is used to analyze the phase composition of the metallographic sample, the scanning step is 0.01/s, and the scanning angle 2θ ranges from 10° to 90°. The obtained high-entropy alloy phase consists of a simple body-centered cubic BCC solid solution.

Scanning electron microscope (SEM) results: After the sample was cut into 10×10×10mm squares by wire cutting, it was carefully ground with metallographic sandpaper of 150#, 400#, 800#, 1200#, 1500# and 2000#, and mechanically After polishing, the coating interface structure was observed using the backscattering mode of the scanning electron microscope. The obtained high-entropy alloy phase composition is shown in Figure 3.

Coating hardness test: use 401MVD digital micro-Vickers hardness tester to measure the microhardness of the alloy. Metallographic sandpaper is carefully ground and mechanically polished. The load loaded during the test is 500g and kept for 15s. 7 points were randomly tested for each sample, and after removing the largest and smallest data, the average value of the remaining 5 data points was taken as the microhardness value of the alloy.

In this embodiment, the laser cladding technology is used to obtain the high-entropy alloy coating. It can be seen from the scanning diagram of Figure 3 that the high-entropy alloy coating is a uniform dendrite structure, and there is an obvious transition layer between the coating and the substrate. , the combination is good, because the thermal conduction direction and thermal conductivity of coating cladding are different, the dendrite morphology is different at different positions of the coating. The surface hardness of the high-entropy total coating is shown in Table 2, and the coating reaches 859.46HV _0.5 after laser cladding.

Table 2 Microhardness of high melting point high entropy alloy laser cladding layer in Example 2

The beneficial effects of the invention are: the high-entropy alloy has a simple body-centered cubic structure, has high strength and thermal stability, and has excellent mechanical properties, and can meet the higher performance requirements of materials in modern industry, especially high temperature Performance requirements; the preparation of the high-entropy alloy coating promotes and expands the application field of the high-entropy alloy; the preparation method is simple, easy to implement, and has broad application prospects.

Although several embodiments of the present invention have been given herein, those skilled in the art should understand that the embodiments herein can be changed without departing from the spirit of the present invention. The above-mentioned embodiments are only exemplary, and the embodiments herein should not be used as limitations on the scope of rights of the present invention.

Claims (6)

1. A high-melting-point high-entropy alloy is characterized in that, the composition of the high-melting-point high-entropy alloy is CoCrMoNbTi; the atomic molar ratio of the above-mentioned components is: Co:Cr:Mo:Nb:Ti=(0.8～1.1) :(0.8～1.1):(0.8～1.1):(0.8～1.1):(0～1.1); Among them, excluding Co:Cr:Mo:Nb:Ti＝(0.8～1.1):(0.8～1.1) :(0.8～1.1):(0.8～1.1):0. 2. high-melting-point high-entropy alloy as claimed in claim 1, is characterized in that, when preparing described high-melting-point high-entropy alloy, the raw material purity of selected Co, Cr, Mo, Nb and Ti is 99%～99.99% %. 3. A preparation method of high-melting-point high-entropy alloy bulk material as claimed in claim 1 or 2, is characterized in that, comprises the steps: Step 1. Surface purification of Co, Cr, Mo, Nb, Ti raw materials to remove oxides; Step 2, Co, Cr, Mo, Nb, Ti according to molar ratio (0.8 ~ 1.1): (0.8 ~ 1.1): (0.8 ~ 1.1): (0.8 ~ 1.1): (0 ~ 1.1) weighing ratio; wherein , excluding Co:Cr:Mo:Nb:Ti=(0.8～1.1):(0.8～1.1):(0.8～1.1):(0.8～1.1):0; Step 3. Put the configured raw materials in the water-cooled copper mold in the vacuum non-consumable tungsten arc melting furnace, vacuumize the electric arc furnace, and the air pressure in the electric arc furnace is 0~6×10 ^-3 Pa; Argon enters the induction cooker, and the pressure reaches 0.4 to 0.6 atmospheres; Step 4. During the smelting process, after the alloy is melted each time, the arc is kept for 30-60s, and the alloy block is turned over after cooling, and this is repeated 3-5 times; after the alloy is evenly smelted, take it out to obtain the high melting point and high entropy alloy. 4. A preparation method of the high-melting-point high-entropy alloy laser cladding coating as claimed in claim 1 or 2, is characterized in that, comprises the steps: Step 1. Mix the powder of the high-melting-point high-entropy alloy in an omnidirectional planetary ball mill, the ball milling speed is 140-160r/min, and the time is 14-16h, and place the uniformly mixed powder on the carbon steel substrate , the preset thickness is 600-800μ m; Step 2. Use high-power laser for multi-channel cladding. The laser power is 2.3-2.7kW, the scanning speed is 300-600mm/min, the spot diameter is 3-4mm, and the overlap rate is 25%-40%. Protect with inert gas. 5. The preparation method according to claim 4, wherein the ball milling speed in step 1 is 150r/min, and the preset thickness of the alloy powder is 700μm. 6. The preparation method according to claim 4, wherein the inert gas in step 2 is Ar.