Heat treatment method for strengthening wear resistance of Ni-Co-C alloy coating

Abstract

The invention provides a heat treatment method for strengthening the wear resistance of a Ni-Co-C alloy coating, and belongs to the technical field of alloy coating preparation. According to the method, grains of the Ni-Co-C alloy coating are effectively refined through subzero treatment, and the stacking fault density is improved, so that dislocation movement is further hindered, and the hardness and wear resistance of the Ni-Co-C alloy coating are improved; according to the method, the residual stress can be slowly released through temperature returning, so that the wear resistance of the Ni-Co-C alloy coating is improved; according to the method, tempering treatment is carried out at the temperature of 150-350 DEG C, so that residual stress caused by excessive lattice distortion can be eliminated, and the wear resistance of the Ni-Co-C alloy coating is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of alloy coating preparation, in particular to a heat treatment method for enhancing the high-temperature wear resistance of a Ni-Co-C alloy coating. Background Art

[0002] The crystallizer is the core component of the continuous casting machine, carrying out key functions such as the initial solidification of molten steel and billet shell forming. Ni-Co-C coating is a multi-element alloy coating for the crystallizer, composed of three elements: Ni, Co and C. While retaining the excellent stability of the binary Ni-Co coating, the addition of C element further improves the comprehensive mechanical properties of the Ni-Co-C coating, and can be applied to a variety of equipment in high-wear-resistant fields to improve the overall mechanical properties of the equipment. However, for some equipment with harsh working environments, such as crystallizers, there are certain challenges. The working environment of the crystallizer is harsh, and its inner wall is subjected to complex stresses caused by the billet drawing process for a long time, resulting in serious defects such as edge wear and cracks. To date, no effective means have been found to further improve the comprehensive performance of the Ni-Co-C coating, represented by high-temperature wear resistance. Summary of the Invention

[0003] The purpose of the present invention is to provide a heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating. The heat treatment method provided by the present invention can enhance the wear resistance of a Ni-Co-C alloy coating at room temperature and high temperature.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating, comprising: sequentially subjecting the Ni-Co-C alloy coating to cryogenic treatment, temperature recovery and tempering treatment;

[0006] The temperature of the cryogenic treatment is 196°C;

[0007] The end point temperature after the temperature is returned to room temperature;

[0008] The temperature of the tempering treatment is 150-350°C.

[0009] Preferably, the components of the Ni-Co-C alloy coating include, by mass percentage, 50.5-55.0% Ni, 42.5-48.0% Co, and 1.5-2.5% C.

[0010] Preferably, the components of the Ni—Co—C alloy coating include, by mass percentage, 52.1% Ni, 45.8% Co and 2.1% C.

[0011] Preferably, the Ni—Co—C alloy coating has a thickness of 40 to 50 μm.

[0012] Preferably, the cryogenic treatment time is 8 to 24 hours.

[0013] Preferably, the cooling rate to the cryogenic treatment temperature is 1-5°C / min.

[0014] Preferably, the temperature recovery method includes: natural temperature recovery in the air.

[0015] Preferably, the heating rate from the final temperature after the temperature return to the tempering temperature is 20-30° C. / min.

[0016] Preferably, the tempering treatment time is 1 to 3 hours.

[0017] Preferably, the tempering treatment cooling method is furnace cooling.

[0018] The present invention provides a heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating, comprising: sequentially subjecting the Ni-Co-C alloy coating to a cryogenic treatment, a reheating treatment, and a tempering treatment; the cryogenic treatment temperature is -196°C; the final temperature after the reheating treatment is room temperature; and the tempering treatment temperature is 150-350°C. The present invention, by performing the cryogenic treatment at -196°C, effectively refines the grains of the Ni-Co-C alloy coating, increases the stacking fault density, thereby further hindering dislocation movement, and increases the hardness of the Ni-Co-C alloy coating, thereby improving the wear resistance of the Ni-Co-C alloy coating. The present invention, by reheating, can slowly release stress, thereby improving the wear resistance of the Ni-Co-C alloy coating. The present invention, by performing the tempering treatment at 150-350°C, can eliminate residual stress caused by excessive lattice distortion, thereby further improving the wear resistance of the Ni-Co-C alloy coating. The results of the embodiment show that the hardness of the Ni-Co-C alloy coating treated by the heat treatment method provided by the present invention is as high as 975.3HV, which is 39.5% higher than the hardness of the untreated Ni-Co-C alloy coating (699.1HV) and 19.1% higher than the hardness of the Ni-Co-C alloy coating that has been cryogenically treated for only 16 hours (819.0HV). The room temperature wear rate of the Ni-Co-C alloy coating treated by the heat treatment method provided by the present invention is 1.1×10 -4 mm 3 / N·m, only the room temperature wear rate of the untreated Ni-Co-C alloy coating (6.0×10 -4 mm 3 / N·m) is 18.3% of the room temperature wear rate of the Ni-Co-C alloy coating that has been cryogenically treated for only 16 h (2.2×10 -4 mm3 / N·m) is 36.7%, showing excellent room temperature wear resistance; the high temperature wear rate of the Ni-Co-C alloy coating treated by the heat treatment method provided by the present invention at 300°C is 2.6×10 -3 mm 3 / N·m, only the high temperature wear rate of the untreated Ni-Co-C alloy coating at 300℃ (7.4×10 -3 mm 3 / N·m) is 35.1%, which is lower than the high temperature wear rate of Ni-Co-C alloy coating subjected to cryogenic treatment for 16h at 300℃ (3.2×10 -3 mm 3 / N·m) decreased by 18.8%, showing excellent high temperature wear resistance. DETAILED DESCRIPTION

[0019] The present invention provides a heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating, comprising: sequentially subjecting the Ni-Co-C alloy coating to cryogenic treatment, temperature recovery and tempering treatment;

[0020] The temperature of the cryogenic treatment is -196°C;

[0021] The end point temperature after the temperature is returned to room temperature;

[0022] The temperature of the tempering treatment is 150-350°C.

[0023] In the present invention, the composition of the Ni-Co-C alloy coating preferably includes, by mass percentage, 50.5-55.0% Ni, 42.5-48.0% Co, and 1.5-2.5% C, and more preferably 52.1% Ni, 45.8% Co, and 2.1% C. The Ni-Co-C alloy coating of the present invention using the above composition has good mechanical properties.

[0024] The present invention does not specifically limit the preparation method of the Ni-Co-C alloy coating, and any conventional alloy coating preparation method can be adopted. In the present invention, the preparation method of the Ni-Co-C alloy coating is preferably a direct current electrodeposition method. In an embodiment of the present invention, the direct current electrodeposition method can be: completing a direct current electrodeposition process with a crystallizer Cu alloy as a matrix in a sulfate electrodeposition solution; the main salts of the sulfate electrodeposition solution can be NiSO4 and CoSO4, the concentration of the NiSO4 can be 100g / L, and the concentration of the CoSO4 can be 10g / L; the carbon source of the direct current electrodeposition can be a carbon-containing reagent, and the carbon-containing reagent can be one or more combinations of ammonium oxalate, sodium oxalate, urea and ammonium citrate, etc., and the concentration of the carbon-containing reagent in the direct current electrodeposition can be 15g / L; the current density of the direct current electrodeposition can be 4A / dm2 The electrodeposition temperature of the direct current electrodeposition can be 50°C, and the electrodeposition time of the direct current electrodeposition can be 4 hours; the anode material of the direct current electrodeposition can be a Ru-Ir alloy-plated titanium plate; the direct current electrodeposition is carried out under stirring, the stirring method can be magnetic stirring, and the stirring rotor speed can be 200r / min.

[0025] In the present invention, the thickness of the Ni-Co-C alloy coating is preferably 40 to 50 μm, more preferably 45 to 50 μm. Since the heat treatment method of the present invention can improve the wear resistance of the Ni-Co-C alloy coating, it can still have a long service life even at the aforementioned thin thickness.

[0026] In the present invention, the temperature of the cryogenic treatment is -196°C. In the present invention, the time of the cryogenic treatment is preferably 8 to 24 hours. As an embodiment of the present invention, the time of the cryogenic treatment can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours. In the present invention, the time of the cryogenic treatment refers to the time of insulation at the temperature of the cryogenic treatment.

[0027] In the present invention, the cooling rate to the cryogenic treatment temperature is preferably 1-5°C / min, more preferably 3-4°C / min. The present invention is more conducive to improving the uniformity of the structure of the Ni-Co-C alloy coating at the above cooling rate.

[0028] In the present invention, the cryogenic treatment is preferably carried out in a cryogenic box containing liquid nitrogen. Cryogenic treatment in the cryogenic box can utilize the latent heat of vaporization of liquid nitrogen to cool the Ni-Co-C alloy coating at the above-mentioned cooling rate and achieve cryogenic treatment within the above-mentioned temperature range.

[0029] In the present invention, the end point temperature after the temperature return is preferably room temperature, more preferably 25° C. By controlling the end point temperature after the temperature return to within the above range, the present invention can return the Ni-Co-C alloy coating to room temperature after cryogenic treatment, thereby preventing the deterioration of the Ni-Co-C alloy coating structure caused by direct tempering treatment after cryogenic treatment.

[0030] In the present invention, the warming method preferably includes natural warming in air. The present invention does not particularly limit the specific time for the warming, as long as the temperature of the cryogenically treated Ni-Co-C alloy coating sample reaches room temperature. The natural warming in air method of the present invention has a slower warming rate, which is beneficial for improving the uniformity of the Ni-Co-C alloy coating structure.

[0031] In the present invention, the temperature of the tempering treatment is 150 to 350°C. As an embodiment of the present invention, the temperature of the tempering treatment may be 150°C, 200°C, 250°C, 300°C or 350°C. In the present invention, the time of the tempering treatment is preferably 1 to 3 hours, more preferably 3 hours. In the present invention, the time of the tempering treatment refers to the time for holding at the tempering treatment temperature. The present invention controls the tempering temperature and time within the above range, which is more conducive to eliminating the residual stress caused by excessive lattice distortion, thereby improving the wear resistance of the Ni-Co-C alloy coating.

[0032] In the present invention, the atmosphere of the tempering treatment is preferably nitrogen. In the present invention, the tempering treatment is preferably performed in an atmosphere furnace.

[0033] In the present invention, the heating rate from the final temperature after the tempering to the tempering temperature is preferably 20-30°C / min, more preferably 20-25°C / min. At this heating rate, the present invention is more conducive to improving the uniformity of the Ni-Co-C alloy coating structure.

[0034] In the present invention, the tempering treatment cooling method is preferably furnace cooling. The present invention has a suitable temperature drop rate through furnace cooling, which can improve the uniformity of the Ni-Co-C alloy coating structure.

[0035] The present invention performs a cryogenic treatment at -196°C, and the stress is slowly released by returning to the original temperature, thereby improving the wear resistance of the Ni-Co-C alloy coating. By performing a tempering treatment at 150-350°C, the residual stress caused by excessive lattice distortion can be eliminated, thereby further improving the wear resistance of the Ni-Co-C alloy coating.

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The method for preparing the Ni-Co-C alloy coating by the direct current electrodeposition method in the embodiment of the present invention is as follows: using NiSO4 with a concentration of 100g / L, CoSO4 with a concentration of 10g / L, and a carbon-containing reagent (oxalic acid) with a concentration of 15g / L as a sulfate electrodeposition solution; using a crystallizer Cu alloy as a matrix and a Ru-Ir alloy-plated titanium plate as an anode material; then stirring at a speed of 200r / min and a current density of 4A / dm 2The Ni-Co-C alloy coating was obtained by electroplating at a temperature of 50°C for 4 h.

[0038] Example 1

[0039] A heat treatment method for enhancing the wear resistance of Ni-Co-C alloy coating:

[0040] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0041] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25°C); then placed in an atmosphere furnace and heated to 150°C at a heating rate of 20°C / min, and then kept at 150°C for 3 hours for tempering, and then cooled with the furnace.

[0042] Example 2

[0043] A heat treatment method for enhancing the wear resistance of Ni-Co-C alloy coating:

[0044] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0045] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25°C); then it was placed in an atmosphere furnace and heated to 250°C at a heating rate of 20°C / min, and then kept at 250°C for 3 hours for tempering, and then cooled with the furnace.

[0046] Example 3

[0047] A heat treatment method for enhancing the wear resistance of Ni-Co-C alloy coating:

[0048] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0049] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25°C); then placed in an atmosphere furnace and heated to 350°C at a heating rate of 20°C / min, and then kept at 350°C for 3 hours for tempering, and then cooled with the furnace.

[0050] Comparative Example 1

[0051] A Ni-Co-C alloy coating is prepared by a direct current electrodeposition method with a deposition time of 4 hours and a coating thickness of 50 μm. Field emission electron microprobe analysis (EPMA) is used to quantitatively analyze the coating composition, and the components, by mass percentage, are: Ni 52.1%, Co 45.8%, and C 2.1%.

[0052] Comparative Example 2

[0053] A heat treatment method for Ni-Co-C alloy coating:

[0054] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0055] The Ni-Co-C alloy coating sample was placed in a cryogenic box and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally returned to 25°C.

[0056] Comparative Example 3

[0057] A heat treatment method for Ni-Co-C alloy coating:

[0058] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0059] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After being kept warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25)°C; then it was placed in an atmosphere furnace and heated to 450°C at a heating rate of 20°C / min, and then kept at 450°C for 3 hours for tempering, and then cooled with the furnace.

[0060] Comparative Example 4

[0061] A heat treatment method for strengthening Ni-Co-C alloy coating:

[0062] A Ni-Co-C alloy coating was prepared by direct current electrodeposition for 4 hours, with a thickness of 50 μm. Field emission electron microprobe analysis (EPMA) was used to quantitatively analyze the coating composition, which was determined to be 52.1% Ni, 45.8% Co, and 2.1% C by mass.

[0063] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25°C); then placed in an atmosphere furnace and heated to 550°C at a heating rate of 20°C / min, and then kept at 550°C for 3 hours for tempering, and then cooled with the furnace.

[0064] Example 4

[0065] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After keeping warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25°C); then placed in an atmosphere furnace and heated to 350°C at a heating rate of 20°C / min, and then kept at 350°C for 1 hour for tempering, and then cooled with the furnace.

[0066] Example 5

[0067] The Ni-Co-C alloy coating sample was placed in a deep freezer and cooled to -196°C at a rate of 5°C / min with the help of the latent heat of vaporization of liquid nitrogen. After being kept warm for 16 hours, it was placed in the air and naturally warmed to room temperature (25)°C; then it was placed in an atmosphere furnace and heated to 350°C at a heating rate of 20°C / min, and then kept at 350°C for 2 hours for tempering, and then cooled with the furnace.

[0068] Test Case

[0069] The microhardness and wear resistance of the Ni-Co-C alloy coatings treated by the methods of Examples 1 to 5 and Comparative Examples 1 to 4 were tested, and the results are shown in Table 1.

[0070] The microhardness test method is as follows: the measurement is performed using an automatic turret Vickers hardness tester model YZHV-1000Z. The load during the experiment is set to 100 gf and the holding time is 10 s.

[0071] The room temperature wear resistance test method is as follows: the room temperature wear resistance is tested using a TBT-M5000 reciprocating friction and wear testing machine. The applied load is 20N and the friction stroke is 20mm.

[0072] The test method for high temperature wear resistance is: use THT07-135 ring-type high temperature friction and wear testing machine to test high temperature wear resistance, the test load is 10N, the friction stroke is 5mm, and the test temperature is 300℃.

[0073] Calculation of coating wear rate: A laser confocal microscope (OLS4100LSCM) was used to obtain the three-dimensional wear morphology and wear volume of the coating, and the wear rate was calculated using formula (1):

[0074]

[0075] In formula (1), w represents the wear rate and V represents the wear volume, and the unit is mm 3 ; F is the load, the unit is N; L represents the friction stroke, the unit is m.

[0076] Table 1 Performance test results of Ni-Co-C alloy coatings obtained by the methods of Examples 1 to 5 and Comparative Examples 1 to 4

[0077]

[0078] As can be seen from Table 1, after 16 hours of cryogenic treatment, the Ni-Co-C alloy coating is tempered at 150℃~350℃ for 1~3 hours, which can further improve the room temperature hardness and wear resistance of the coating. Among them, the strengthening effect after tempering at 350℃ for 3 hours is the most significant; after tempering at 550℃, the hardness and wear resistance of the coating deteriorate due to the high temperature softening of the coating. Specifically, the hardness of the coating after cryogenic treatment for 16 hours + tempering at 350℃ for 3 hours is as high as 975.3HV, which is 39.5% higher than the hardness of the untreated Ni-Co-C alloy coating (699.1HV) and 19.1% higher than the hardness of the Ni-Co-C alloy coating that has only been cryogenically treated for 16 hours (819.0HV). The room temperature wear rate of the Ni-Co-C alloy coating treated by the heat treatment method provided by the present invention is 1.1×10 -4 mm 3 / N·m, only the room temperature wear rate of the untreated Ni-Co-C alloy coating (6.0×10 -4 mm 3 / N·m) is 18.3% of the room temperature wear rate of the Ni-Co-C alloy coating that has been cryogenically treated for only 16 h (2.2×10 -4 mm 3 / N·m) is 36.7%, showing excellent room temperature wear resistance; the high temperature wear rate of the Ni-Co-C alloy coating treated by the heat treatment method provided by the present invention at 300°C is 2.6×10 -3 mm 3 / N·m, only the high temperature wear rate of the untreated Ni-Co-C alloy coating at 300℃ (7.4×10 -3 mm 3 / N·m) is 35.1%, which is lower than the high temperature wear rate of Ni-Co-C alloy coating subjected to cryogenic treatment for 16h at 300℃ (3.2×10 -3 mm 3 / N·m) decreased by 18.8%.

[0079] Therefore, after treatment with the heat treatment method provided by the present invention, the room temperature and high temperature wear resistance of the Ni-Co-C alloy coating can be significantly enhanced. Applying it to the inner surface of the crystallizer in the actual continuous casting process will further improve the wear resistance of the crystallizer, thereby increasing the overall service life of the crystallizer.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating, comprising: The Ni-Co-C alloy coating is subjected to cryogenic treatment, temperature recovery and tempering treatment in sequence; The temperature of the cryogenic treatment is -196°C; The end point temperature after the temperature is returned to room temperature; The temperature of the tempering treatment is 150-350°C.

2. The heat treatment method for enhancing the wear resistance of the Ni-Co-C alloy coating according to claim 1, characterized in that: Calculated by mass percentage, the components of the Ni-Co-C alloy coating include: Ni 50.5-55.0%, Co 42.5-48.0% and C 1.5-2.5%.

3. The heat treatment method for enhancing the wear resistance of the Ni-Co-C alloy coating according to claim 2, characterized in that: Calculated by mass percentage, the components of the Ni—Co—C alloy coating include: 52.1% Ni, 45.8% Co and 2.1% C.

4. The heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating according to any one of claims 1 to 3, characterized in that: The thickness of the Ni-Co-C alloy coating is 40-50 μm.

5. The heat treatment method for enhancing the wear resistance of the Ni-Co-C alloy coating according to claim 1, characterized in that: The cryogenic treatment time is 8 to 24 hours.

6. The heat treatment method for enhancing the wear resistance of the Ni-Co-C alloy coating according to claim 1, characterized in that: The cooling rate to the cryogenic treatment temperature is 1-5°C / min.

7. The heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating according to claim 1, characterized in that: The temperature recovery method includes: natural temperature recovery in the air.

8. The heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating according to claim 1, characterized in that: The heating rate from the final temperature after the temperature return to the tempering temperature is 20-30°C / min.

9. The heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating according to claim 1, characterized in that: The tempering treatment time is 1 to 3 hours.

10. The heat treatment method for enhancing the wear resistance of a Ni-Co-C alloy coating according to claim 1, characterized in that: The tempering treatment cooling method is furnace cooling.

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