A high-temperature component surface cBN reinforced NiCrAlY cermet composite powder, coating and preparation method thereof

Abstract

The present application relates to the technical field of cermet high-temperature protective coating, in particular to a cBN reinforced NiCrAlY cermet composite powder on the surface of high-temperature parts, a coating and a preparation method thereof, wherein the cBN ceramic particles with high hardness, high thermal conductivity and corrosion resistance are fused into the NiCrAlY alloy by a mechanical alloying method to prepare the cBN reinforced NiCrAlY cermet composite powder with a particle size in the range of 18-57 microns, which is suitable for thermal spraying, and then the oxygen-kerosene supersonic flame spraying technology is used to spray on the surface of the substrate to prepare the NiCrAlY-cBN composite coating. The composite coating is suitable for improving the high-temperature oxidation resistance and high-temperature wear resistance of the surface of the easily-worn parts in high-temperature environments such as furnace rollers, and improving the mechanical service life in high-temperature environments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cermet high-temperature protective coating, in particular to a cBN reinforced NiCrAlY cermet composite powder for high-temperature part surface, a coating and a preparation method thereof. BACKGROUND

[0002] Modern industrial equipment in the fields of metallurgy and chemical industry, for example, is required to serve in high-temperature environment for a long time, such as the conveying roller of a continuous annealing line for strip steel, the surface of a rotary joint of a converter, a submerged roller in a hot-dip plating unit, etc., and the operating temperature can be as high as 700 DEG C. High-temperature parts are required to have the following four aspects of problems in the harsh environment of high load and high temperature for a long time: 1) the equipment needs to maintain stable mechanical properties in the high-temperature environment during production operation; 2) friction and wear occurring in the high-temperature environment; 3) surface high-temperature oxidation leading to failure of the surface structure of the part; and 4) corrosion in the high-temperature working environment in metallurgy and chemical industry. These problems affect the normal operation of the equipment, seriously affect the quality stability of the product, greatly shorten the service life of the high-temperature part, and even bring about production safety hazards.

[0003] MCrAlY alloy (M refers to Ni, Co, ) has good high-temperature oxidation resistance at high temperature, especially in the range of 900 DEG C to 1150 DEG C, so it has important research significance in the field of high-temperature part protective coating and is often used as the matrix phase of cermet coating. However, the wear resistance of the coating is relatively weak, and the disadvantage of MCrAlY alloy in this respect can be improved by adding a ceramic reinforcing phase. In the current research on reinforcing phases, carbide ceramics are prone to decarburization at high temperatures; oxide ceramics cause the coating to peel off due to the mismatch between the thermal expansion coefficient and the metal phase. As a strengthening material, cBN ceramic has high hardness (9MH), high melting point (2973 DEG C), high thermal conductivity (1300 W / mK), low density (3.44 g / cm 3 ), low thermal expansion coefficient (3.5 x 10 -6 / K), and good oxidation resistance. The NiCrAlY alloy coating has excellent oxidation resistance, but its hardness is low and its wear resistance is poor. The addition of cBN in NiCrAlY can increase the hardness and wear resistance of the coating without affecting its oxidation resistance. At present, in addition to directly using commercial powders, the commonly used method for self-preparing cermet powder is mechanical mixing. However, the coating obtained by spraying the cermet powder prepared by the mechanical mixing method has a clear interface between the metal phase and the ceramic phase and uneven composition distribution, which seriously limits the play of the strength and toughness of the metal phase and the wear and corrosion resistance of the ceramic phase.

[0004] In view of the above-mentioned defects, the present inventors have finally obtained the present application after long-term research and practice. SUMMARY

[0005] The present application aims at solving the problem of uneven distribution of metal phase and ceramic phase in the coating prepared by spraying the cermet powder prepared by the mechanical mixing method, and provides a cBN reinforced NiCrAlY cermet composite powder for the surface of high-temperature components, a coating and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the present application discloses a preparation method of a cBN reinforced NiCrAlY cermet composite powder for the surface of high-temperature components, comprising the following steps:

[0007] S1, uniformly mixing NiCrAlY and cBN powder in proportion;

[0008] S2, ball milling the mixed powder obtained in step S1 in an argon environment;

[0009] S3, obtaining 15-60 mu m NiCrAlY-cBN cermet powder through a screening machine from the powder obtained after ball milling in step S2.

[0010] In the step S1, the particle size of the NiCrAlY powder is 15-45 mu m, and the mass percentage of the elements is Cr 10-30%, Al 10-20%, Y 0.5-1%, and the balance is Ni; the particle size of the cBN powder is 1-3 mu m, and the purity is greater than or equal to 99.5%.

[0011] In the step S1, the mass ratio of NiCrAlY to cBN powder is 9-7:1-3, the mixing speed is 60 r / min, and the mixing time is 2 h. If the mass ratio of NiCrAlY to cBN powder is too small, the particle size range is too large, and it cannot be sprayed; if the mass ratio is too large, the ceramic phase cannot be uniformly distributed in the metal phase, and part of the ceramic phase cannot enter the metal phase.

[0012] In the step S2, the mixed powder of NiCrAlY and cBN is added to a steel ball milling tank and alloyed by using a ball mill; GCr15 steel grinding balls are used, and the grinding balls are selected in diameters of 15 mm, 10 mm, 6 mm and 5 mm, and mixed grinding balls are prepared in a mass ratio of 1:4:2:1; the mass ratio of the grinding balls to the powder in the tank is kept at 10:1; the pressure of the vacuum pump connected to the ball milling tank is set to 10 Pa, the time is kept for 10 min, argon is filled at a pressure of 0.12 MPa for 3 min, and the cycle is 3 times.

[0013] The parameters of the ball mill are as follows: the speed is 220 rpm, and the ball milling time is 50-60 h.

[0014] The present application also discloses a cBN reinforced NiCrAlY cermet composite powder for the surface of high-temperature components prepared by the above preparation method.

[0015] The application also discloses a high-temperature part surface cBN reinforced NiCrAlY cermet composite coating prepared from the above-mentioned cermet composite powder, wherein the thickness of the NiCrAlY-cBN cermet composite coating is 150-200 microns, the hardness is 600-770 HV, and the porosity of the coating is 0.28-0.45%. 0.3

[0016] The application also discloses a preparation method of the high-temperature part surface cBN reinforced NiCrAlY cermet composite coating.

[0017] (1) before spraying, the surface of the high-temperature part substrate is subjected to oil removal cleaning treatment, and then the surface is subjected to sand blasting cleaning and roughening treatment;

[0018] (2) the supersonic flame spraying technology of an oxygen-kerosene system is used as a coating preparation means, first, the surface of the sprayed substrate is subjected to air spraying preheating, and then the cermet composite powder is sprayed to form the NiCrAlY-cBN cermet composite coating on the surface of the part.

[0019] In the step (1), the sand blasting material is brown corundum sand with a particle size of 25 mesh, the sand blasting pressure is 0.5 MPa, and the surface roughness of the substrate after sand blasting is 5.4-6.0 microns.

[0020] In the step (2), the process parameters of the oxygen-kerosene system are as follows: the oxygen flow is 53 m 3 / h, the kerosene flow is 28-32 L / h, the spraying distance is 340 mm, the spraying step distance is 3 mm, the spraying speed is 800 mm / s, the powder feeding rate is 30 g / min, and the substrate preheating temperature is 80-120 DEG C.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] 1. The cermet composite powder prepared by the high-energy ball milling mechanical alloying method has a near-spherical shape, so that the powder has a certain fluidity and the powder particle size is uniform. The cBN ceramic phase is uniformly dispersed in the NiCrAlY matrix phase, which overcomes the shortcomings of the powder prepared by the traditional mechanical mixing method, i.e. the metal phase and the ceramic phase are unevenly distributed in the sprayed layer.

[0023] 2. The composite coating prepared by the application has good oxidation resistance and wear resistance at 700 DEG C, and the service life of the mechanical part in a high-temperature environment is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a schematic diagram of the step-by-step mechanical alloying process in the application;

[0025] ​Figure 2 The morphology of NiCrAlY-cBN composite powder prepared by a stepwise mechanical alloying process, wherein (a) is the powder ball-milled for 50h, (b) is the powder ball-milled for 55h, and (c) is the powder ball-milled for 60h;

[0026] Figure 3 The cross-sectional morphology and corresponding point EDS composition results of NiCrAlY-cBN composite powder prepared by a stepwise mechanical alloying process, wherein (a) is the powder ball-milled for 50h, (b) is the powder ball-milled for 55h, and (c) is the powder ball-milled for 60h;

[0027] Figure 4 The particle size distribution and average particle size of NiCrAlY-cBN composite powder prepared by a stepwise mechanical alloying process, wherein (a) is the powder ball-milled for 50h, (b) is the powder ball-milled for 55h, and (c) is the powder ball-milled for 60h;

[0028] Figure 5 The surface and cross-sectional morphology of NiCrAlY-cBN composite coating prepared at different kerosene flow rates, wherein (a) is 28L / h, (b) is 30L / h, and (c) is 32L / h;

[0029] Figure 6 The surface morphology of the friction area and the non-friction area of the NiCrAlY-cBN composite coating prepared by the supersonic flame spraying process under the environment of 700℃, and the comparison diagram of the wear rate of the NiCrAlY coating under 700℃, wherein (a) is the surface of the wear scar, (b) is the oxidized surface, and (c) is the comparison of the wear rate of the NiCrAlY coating. DETAILED DESCRIPTION

[0030] The above and other technical features and advantages of the present application will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0031] Example 1

[0032] As shown in the following, Figure 1 according to the mechanical alloying process,

[0033] S1, first, the NiCrAlY powder and cBN powder were weighed in a mass ratio of 9:1 (NiCrAlY 180 g, cBN 10 g) and placed in a premixer for mixing for 2 h. After mixing, the mixture was taken out and placed in a stainless steel ball mill jar. The grinding balls were placed in the ball mill jar in a mass ratio of 10:1 to the powder. The grinding balls were configured in a mass ratio of 15 mm:10 mm:6 mm:5 mm = 1:4:2:1. The ball mill jar was then filled with argon, the vacuum pump pressure was set to 10 Pa, the ball mill jar was connected for 10 min, and the argon was filled at a pressure of 0.12 MPa for 3 min, with 3 cycles. Dry milling was used, with a rotation speed of 220 rpm and a time of 50 h.

[0034] S2, after the ball milling and alloying, the composite powder was taken out and sieved. A metal sieve with a mesh size of 15 μm and 60 μm was used to sieve the powder, to obtain a NiCrAlY-cBN cermet powder with a particle size distribution of 15-60 μm.

[0035] The method for preparing the NiCrAlY-cBN composite coating for high-temperature protection of the surface of a high-temperature component mainly comprises the following steps:

[0036] (1) Before spraying, the surface of the high-temperature component was cleaned and degreased using a detergent, alcohol or acetone, and then the cleaned surface was sandblasted to roughen the surface. The sandblasting material was brown corundum sand with a particle size of 25 mesh, and the sandblasting pressure was adjusted to 0.5 MPa. After sandblasting, the surface roughness of the substrate was 5.4-6.0 μm.

[0037] (2) The power, gas circuit switch and cooling water switch of the spraying equipment were turned on, oxygen was used as the combustion aid, kerosene was used as the fuel, and nitrogen was used as the powder feeding carrier gas. The sample was fixed on the workbench, the running program of the mechanical arm was modified, the spraying distance was set to 340 mm, the spraying speed was 800 mm / s, and the spraying step was 3 mm.

[0038] (3) The flow rate valves of kerosene and oxygen were adjusted, the oxygen flow rate was adjusted to 53 m 3 / h, the kerosene flow rate was 32 L / h, the kerosene flame was ignited to preheat the surface of the substrate to a temperature of 80-120 °C, the powder feeder switch was turned on, and the 50 h ball-milled and alloyed composite powder was fed into the supersonic spraying system, so that the powder feeding rate was maintained at 30 g / min. After every 3 passes of spraying, the coating surface was cooled by blowing with an air gun, and the coating thickness was measured using a screw micrometer. When the coating temperature was reduced to about 70 °C, the spraying equipment was started again for spraying, and the operation was repeated until the coating thickness reached about 180 μm.

[0039] Example 2

[0040] The difference between the present example and Example 1 is that the ball milling time in the dry milling method in step S1 is 55 h, and other steps are the same as in Example 1.

[0041] Example 3

[0042] The difference between the present example and Example 1 is that the ball milling time in the dry milling method in step S1 is 60 h, and other steps are the same as in Example 1.

[0043] Example 4

[0044] The difference between the present example and Example 1 is that the flow rate of kerosene in step (3) is 28 L / h, and other steps are the same as in Example 1.

[0045] Example 5

[0046] The difference between the present example and Example 1 is that the flow rate of kerosene in step (3) is 30 L / h, and other steps are the same as in Example 1.

[0047] Comparative Example

[0048] In the present comparative example, a commercial NiCrAlY powder is used to prepare a NiCrAlY coating by supersonic flame spraying, and the supersonic flame spraying steps are the same as the steps for preparing the NiCrAlY-cBN composite coating in Example 1.

[0049] I. Performance testing and selection of the NiCrAlY-cBN composite powder prepared in Examples 1-3

[0050] Three nodes of 50 h, 55 h and 60 h in the optimal ball milling time range are selected as example powders, and after the powders are prepared, the particle state of the composite powders is observed, as shown in Figure 2 The particles are in a group state and have fluidity, and the morphology meets the requirements of thermal spraying powder feeding. The phase observation of the powder is performed, as shown in Figure 3 , 4 The internal phase distribution of the comparative powder is shown in

[0051] II. Performance testing and selection of the NiCrAlY-cBN composite coating prepared in Examples 1, 4, 5 and the comparative example and the NiCrAlY coating

[0052] As shown in Figure 5As shown, three kerosene flow rates of 28, 30, and 32 L / h were selected to prepare the coating as an example, and the three NiCrAlY-cBN composite coatings were named K1, K2, and K3 in turn. By comparing the cross-sectional phase distribution of the K1, K2, and K3 coatings, the phase distribution of the K3 coating was more uniform, and the black cBN ceramic phase was distributed throughout the coating. Uniform phase distribution can maintain the stability of the coating performance.

[0053] The microhardness of the coating was tested using a small load Vickers hardness tester, the load was 2.94 N, the loading time was 15 s, 15 points of each coating were tested, and the average value was taken as the microhardness value of the coating. The test results are shown in Table 1.

[0054] Table 1 Microhardness of the NiCrAlY-cBN composite coating and the NiCrAlY coating prepared in Examples 1 and 2

[0055]

[0056] The high-temperature wear performance test method of the NiCrAlY-cBN composite coating and the NiCrAlY coating prepared in Examples 1 and Comparative Examples is as follows:

[0057] The K3 NiCrAlY-cBN composite coating and the NiCrAlY coating were tested for high-temperature wear using a UMT TriboLab high-temperature ball-on-disc friction and wear module, the test conditions were a load of 10 N, a temperature of 700°C, a friction radius of 4 mm, and a wear time of 60 min. The coating was paired with a Si3N4 ceramic ball with a diameter of 6.35 mm. After the high-temperature friction test, the wear scar of the coating was scanned using a Rtec UP Series white light interferometer, and the wear volume of the coating was calculated, and then the wear rate of the coating was calculated according to the wear rate formula.

[0058] The wear rate formula is: W = V / PL, V = πdS, V is the wear volume (m 3 ), d is the wear scar track diameter (m), S is the wear scar cross-sectional missing area (m 2 ) calculated by Origin software data fitting, P is the wear loading load (N), and L is the wear distance (m). The composite coating and the calculation results after 700°C wear are shown in Figure 6 As shown, the non-wear area was not covered by an obvious oxidation layer, and the distribution of cBN particles in the coating was clearly observed, and the surface O content was below 4%. Compared with the NiCrAlY coating, the NiCrAlY-cBN composite coating prepared in Example 1 had a lower wear rate at a high temperature of 700°C, and the addition of cBN ceramic made it have better wear resistance.

[0059] Figure 6The EDS results of the corresponding points of the medium friction area and the non-friction area surface are compared as shown in Table 2,

[0060] Table 2 Figure 6 The EDS results of the corresponding points of the medium friction area and the non-friction area surface are compared

[0061] Element symbol (wt%) O Ni Cr Al B N 1 26.47 49.79 18.13 5.62 - - 2 4.89 64.49 24.75 5.03 - - 3 2.46 68.25 25.45 3.84 - - 4 3.96 59.63 23.82 4.75 1.75 5.37

[0062] In summary, the NiCrAlY-cBN composite coating prepared by the application meets the requirements of high-temperature oxidation resistance and high-temperature wear resistance of the surface of high-temperature components, and the best powder and coating preparation process are obtained by improving the process flow. The cermet composite powder with a mass ratio of NiCrAlY powder to cBN powder of 9:1 is prepared by a mechanical alloying process; the spraying process parameters are as follows: the flow rate of kerosene is 32L / h, the flow rate of oxygen is 53m 3 / h, the spraying distance is 340mm, the spraying step distance is 3mm, the spraying speed is 800mm / s, and the powder feeding rate is 30g / min, and the composite coating prepared under the parameters has good high-temperature wear resistance.

[0063] The above description is only the preferred embodiment of the application, which is only illustrative but not limiting. Those skilled in the art understand that many changes, modifications and even equivalents can be made to the application within the spirit and scope of the application defined in the claims, and all will fall within the protection scope of the application.

Claims

1. A method for preparing cBN-reinforced NiCrAlY cermet composite powder for the surface of high-temperature components, characterized in that, Includes the following steps: S1, NiCrAlY and cBN powder are mixed evenly in proportion; S2, the mixed powder obtained in step S1 is ball-milled in an argon atmosphere; S3, the powder obtained after ball milling in step S2 is sieved to obtain NiCrAlY-cBN metal ceramic powder with a thickness of 15~60μm; In step S1, the NiCrAlY powder has a particle size of 15-45 μm, and the elemental mass percentage is Cr 10-30%, Al 10-20%, Y 0.5-1%, with the balance being Ni. The cBN powder has a particle size of 1-3 μm and a purity ≥99.5%. In step S1, the mass ratio of NiCrAlY to cBN powder is 9-7:1-3, the mixing speed is 60 r / min, and the mixing time is 2 h. In step S2, the NiCrAlY and cBN powder is mixed and added to a steel ball mill jar for high-energy ball milling alloying. GCr15 steel grinding balls are used for milling, with diameters of 15mm, 10mm, 6mm, and 5mm selected and mixed in a mass ratio of 1:4:2:

1. The mass ratio of grinding balls to powder in the jar is maintained at 10:

1. The vacuum pump connected to the ball mill jar is set to a pressure of 10Pa and maintained for 10 minutes. Argon gas is charged at a pressure of 0.12MPa for 3 minutes, and the cycle is repeated 3 times. The parameters of the ball mill are: rotation speed of 220rpm and ball milling time of 50-60h.

2. A high-temperature component surface cBN-reinforced NiCrAlY cermet composite powder prepared by the preparation method described in claim 1.

3. A cBN-reinforced NiCrAlY metal-ceramic composite coating on the surface of a high-temperature component, prepared using the metal-ceramic composite powder as described in claim 2, characterized in that, The NiCrAlY-cBN cermet composite coating has a thickness of 150–200 μm and a hardness of 600–770 HV. 0.3 The porosity of the coating is 0.28~0.45%.

4. A method for preparing a cBN-reinforced NiCrAlY cermet composite coating on the surface of a high-temperature component as described in claim 3, characterized in that, Includes the following steps: (1) Before spraying, the surface of the high-temperature component substrate is degreased and cleaned, and then the surface is sandblasted and roughened. (2) Using the oxygen-kerosene system supersonic flame spraying technology as the coating preparation method, the substrate surface to be sprayed should first be preheated by air spraying, and then metal-ceramic composite powder should be sprayed to form a NiCrAlY-cBN metal-ceramic composite coating on the surface of the component.

5. The method for preparing a cBN-reinforced NiCrAlY cermet composite coating on the surface of a high-temperature component as described in claim 4, characterized in that, In step (1), the blasting material is 25-mesh brown corundum sand, the blasting pressure is 0.5 MPa, and the surface roughness of the substrate after blasting is 5.4~6.0 μm.

6. The method for preparing a cBN-reinforced NiCrAlY cermet composite coating on the surface of a high-temperature component as described in claim 4, characterized in that, In step (2), the process parameters of the oxygen-kerosene system are: oxygen flow rate 53 m³ / h. 3 / h, kerosene flow rate is 28~32L / h, spraying distance is 340mm, spraying step is 3mm, spraying speed is 800mm / s, powder feeding rate is 30g / min, and substrate preheating temperature is 80~120℃.

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