Ferritic martensitic steel with coating and method for producing the coating
Technical Field
The invention relates to the technical field of ferrite martensite steel surface modification, in particular to ferrite martensite steel with a coating and a preparation method of the coating.
Background
The ferritic martensitic steel has the advantages of high yield strength, high elongation, strong impact toughness and the like, is widely applied to the fields of automobiles, petroleum and natural gas pipelines and large engineering machinery, and is generally considered as a first-choice structural material of future fusion demonstration reactors and fusion power reactors because of excellent thermophysical and mechanical properties such as lower radiation swelling and thermal expansion coefficients and higher thermal conductivity.
The ferritic martensitic steel is used as a lead-bismuth fast reactor cladding structure material, however, in the service process, the ferritic martensitic steel needs to be used in severe environments such as strong irradiation, high temperature, corrosion, mechanics and the like. Therefore, higher requirements are put on the properties of the ferritic martensitic steel to ensure the safety of the nuclear reactor, including improving the hardness, wear resistance, oxidation resistance and the like.
In the prior art, a coating is usually provided on the surface of the ferritic martensitic steel, the coating mainly adopts alumina as a raw material, and the coating is usually provided on the surface of the ferritic martensitic steel by adopting a chemical deposition mode. However, in the using process, the coating layer is disposed on the surface of the ferritic martensitic steel by using a chemical deposition method, so that the corrosion resistance effect of the ferritic martensitic steel is mainly improved, and further research is needed for improving the hardness of the ferritic martensitic steel.
Disclosure of Invention
In order to solve the above problems, the present invention provides a ferritic martensitic steel having a coating layer capable of improving the hardness of the ferritic martensitic steel and a method for preparing the coating layer.
A method for preparing a coating of ferritic martensitic steel, characterized by comprising the steps of:
s1, preprocessing the surface of the substrate;
s2, preparing a cladding agent: weighing raw materials, uniformly mixing the raw materials, and stirring the raw materials and a PVA organic solvent with the concentration of 6-8 wt.% to form a paste to form a cladding agent;
s3, coating the cladding agent on the surface of the matrix, and drying;
s4, carrying out laser cladding treatment on the dried matrix coated with the cladding agent, and adopting inert gas as protective gas;
s5, taking out the clad substrate, and then polishing the substrate with the cladding coating on the surface to be smooth;
in S5, the laser cladding process parameters are as follows: the laser power is 50-100W, the pulse width is 2.5-5 m.s, the defocusing amount is 2mm, and the scanning speed is 5 mm/s.
By adopting the technical scheme, in the parameter range of the laser cladding treatment, the cladding agent is cladded on the surface of the substrate to form the coating, second-phase particles exist in the coating, the atomic size of the second-phase particles is different from that of the surrounding coating tissue, serious lattice distortion is generated, dislocation movement is effectively blocked, and the coating generates a remarkable hardening effect, so that the strength of the surface of the substrate is improved; the higher the laser power, the deeper the laser modification depth.
Preferably, in S1, when the surface of the substrate is pretreated, a plurality of different types of sandpaper are used, and the surface of the substrate is rotated by 90 ° every time the different types of sandpaper are changed.
Through adopting above-mentioned technical scheme, when trading the abrasive paper of different models, the base member surface is rotatory 90 for the effect of polishing of base member is better.
Preferably, in S3, the thickness of the cladding agent coated on the surface of the substrate is 150-180 μm.
By adopting the technical scheme, when the coating thickness of the cladding agent is 150-180 mu m, the hardness of the coating matrix formed by cladding is optimal.
Preferably, the overall depth of the laser modification region in S4 is 80-530 μm.
By adopting the technical scheme, in the parameter selection range, the second-phase particles exist in the coating, and the higher the laser power is, the deeper the laser modification depth is.
A ferrite martensite steel with a coating is prepared by a coating preparation method of the ferrite martensite steel.
Preferably, the coating comprises a coating layer and a substrate, wherein the raw material of the coating layer comprises Al2O3Second phase particles present in the coating, the second phase particles being Al2O3Particles, the second phase particles differing from the atomic size of the surrounding coating structure and causing lattice distortion of the coating, the substrate being a ferritic martensitic steel.
By adopting the technical scheme, a large number of fine dispersed second-phase particles exist in the coating, and the second-phase particles are Al2O3The atomic size of the particles, the second phase particles and the surrounding coating structure is different, so that lattice distortion occurs in the coating, dislocation motion is effectively hindered, and a remarkable hardening effect is generated on the surface of the substrate.
Preferably, the raw material of the coating also comprises Fe, Cr and Ni elements, and the coating generates grain refinement.
By adopting the technical scheme, Fe, Cr and Ni elements are added in the raw materials, so that fine lath martensite is generated in the coating, the average grain size of the coating is obviously reduced, a remarkable fine grain strengthening effect is generated, and the hardness of the coating is further improved.
Preferably, the Al is2O3The mass ratio of Fe, Cr and Ni elements is 16.2: 68.4: 9: 10.
by adopting the technical scheme, Al in the coating raw material2O3The mass ratio of Fe, Cr and Ni elements is 16.2: 68.4: 9: when 10, the hardness of the coating layer with the raw materials with the mixture ratio is better.
Preferably, the Al is2O3Fe, Cr andand the mass ratio of the Ni element is 17.1: 68.4: 9.5: 5.
by adopting the technical scheme, Al in the coating raw material2O3The mass ratio of Fe, Cr and Ni elements is 17.1: 68.4: 9.5: 5, the hardness of the coating with the raw materials with the mixture ratio is optimal.
In conclusion, the invention has the following beneficial effects:
1. the invention melts and coats a coating on the surface of a substrate by pulse laser, wherein the substrate is made of ferrite martensitic steel, and the coating comprises Al as a raw material2O3Second phase particles exist in the cladding layer, the atomic sizes of the second phase particles and the surrounding coating structure are different, severe lattice distortion occurs, dislocation motion is effectively hindered, and the surface of the substrate generates a remarkable hardening effect.
2. The coating raw material of the invention is Al2O3Fe, Cr and Ni, so that the coating not only generates second phase particles, but also generates fine crystal strengthening after cladding, and further improves the hardness of the surface of the matrix.
3. Coating Material Al of the invention2O3The mass ratio of Fe, Cr and Ni elements is 17.1: 68.4: 9.5: 5, the hardness of the coating with the raw materials in the ratio is optimal.
Drawings
FIG. 1 is a graph comparing hardness of a substrate of example 1 of the present invention with that of a coated substrate;
FIG. 2 is an ECC plot of the surface of a coated substrate of example 1 of the present invention;
FIG. 3 is a graph of EDS surface scans of a second phase in the coating of example 1 of the present invention;
FIG. 4 is a graph comparing hardness of the substrate of example 2 of the present invention with that of the coated substrate;
FIG. 5 is an ECC plot of the surface of a coated substrate of example 2 of the present invention;
FIG. 6 is a graph of EDS surface scans of a second phase in a coating of example 2 of the present invention;
FIG. 7 is a graph comparing hardness of the substrate of example 3 of the present invention with that of the coated substrate;
FIG. 8 is an ECC plot of the surface of a coated substrate of example 3 of the present invention;
FIG. 9 is a graph of EDS surface scans of a second phase in the coating of example 3 of the present invention;
FIG. 10 is a graph comparing hardness of the substrate of example 4 of the present invention with that of the coated substrate;
FIG. 11 is an ECC plot of the surface of a coated substrate of example 4 of the present invention;
FIG. 12 is a graph of EDS surface scans of a second phase in the coating of example 4 of the present invention;
FIG. 13 is a graph comparing hardness of the substrate of example 5 of the present invention with that of the coated substrate;
FIG. 14 is an ECC plot of the surface of the coated substrate of example 5 of the present invention;
FIG. 15 is a graph of EDS surface scans of a second phase in a coating of example 5 of the present invention;
FIG. 16 is a graph comparing hardness of the substrate of example 6 of the present invention with that of the coated substrate;
FIG. 17 is an ECC plot of the surface of a coated substrate of example 6 of the present invention;
FIG. 18 is a graph of EDS surface scan results for a second phase in a coating of example 6 of the invention.
Detailed Description
The laser cladding technology is that a layer of required coating material is pre-coated on the surface of a cladded substrate in advance, then the coating and the thin layer of the substrate surface are simultaneously melted through laser irradiation, and the coating and the thin layer of the substrate surface are rapidly solidified to form a surface coating which is metallurgically combined with the cladded substrate.
The present invention will be described in further detail with reference to examples.
The raw materials adopted by the invention are all commercial products, wherein the matrix is ferrite martensite steel (the size is 15 multiplied by 10 multiplied by 2mm) with the mark of HT-9, and Al2O3The purity of the Fe, Cr and Ni powders was 99.9%.
Example 1
A method for preparing a coating of ferritic martensitic steel comprises the following steps:
and S1, preprocessing the surface of the base body, sequentially selecting 400#, 800#, 1000#, and 1200# sandpaper to polish the surface of the base body, rotating the base body of the sandpaper with different values for 90 degrees, and then water-polishing the base body by using 2000# and 3000# sandpaper until the surface of the base body is bright. And cleaning the polished substrate with absolute ethyl alcohol, and finally drying the surface of the substrate.
S2, preparing a cladding agent, and weighing 100g of Al2O3The powder is stirred with PVA organic solvent with the concentration of the organic solvent being 6 wt.% to prepare pasty cladding agent.
S3, using a glass scraper to flatly coat the mixed cladding agent on the surface of the substrate, wherein the coating thickness is 150 μm, and then putting the substrate coated with the coating into an oven to dry, wherein the drying temperature of the oven is 120 ℃, and the drying time is 10 h.
S4, carrying out laser cladding treatment on the dried matrix coated with the cladding agent, clamping the matrix on a clamp of a pulse laser with the model number of 600WNd: YAG, and placing the matrix on a working station of a working chamber of pulse laser equipment; in the working process, inert gas is used as protective gas, argon with the purity of 99.9 percent is used as the inert gas, and the flow rate of the argon is 5L/min-1The laser power is 50W, and the energy density is 12.5J/mm2The pulse width was 2.5m · s, the defocus amount was 2mm, the scanning speed was 5mm/s, and the scanning direction was along the RD direction, and a lap ratio of 50% was achieved by moving the laser beam back and forth.
S5, taking down the substrate from the clamp, cladding the cladding agent on the surface of the substrate to form an integral coating, and then polishing through SiC abrasive paper (1200# -3000#) to enable the side surface of the substrate with the coating to be flat; electropolishing (polishing at-30 ℃ C. and 20V for 1min) was performed in a mixed solution of 90mL of ethanol and 10mL of perchloric acid.
Example 2
The difference from example 1 is that in S2, the concentration of PVA organic solvent was 8 wt.%; in S3, the coating thickness was 180 μm; in S4, the laser power was 100W, and the pulse width was 5m · S.
Example 3
The difference from example 1 is that 16.2g of Cr, 68.4g of Fe, 9g of Ni, and 10g of Al were weighed in S22O3Putting the mixture into a ball mill, mixing the mixture for 12 hours at the rotating speed of 70r/min, and stirring the mixture with a PVA organic solvent with the concentration of the organic solvent being 6 wt.% to prepare the pasty cladding agent.
Example 4
The difference from example 3 is that in S2, the concentration of PVA organic solvent was 8 wt.%; in S3, the coating thickness was 180 μm; in S4, the laser power was 100W, and the pulse width was 5m · S.
Example 5
The difference from example 1 is that in S2, 17.1g of Cr, 68.4g of Fe, 9.5g of Ni, and 5g of Al were weighed2O3Putting the mixture into a ball mill, mixing the mixture for 12 hours at the rotating speed of 70r/min, and stirring the mixture with a PVA organic solvent with the concentration of the organic solvent being 6 wt.% to prepare the pasty cladding agent.
Example 6
The difference from example 5 is that in S2, the concentration of PVA organic solvent was 8 wt.%; in S3, the coating thickness was 180 μm; in S4, the laser power was 100W, and the pulse width was 5m · S.
Performance test
Detection method
Modification depth: the measurement was performed using particle size distribution calculation software.
Hardness: hardness measurements were made on the cross section (TD-ND surface) of the coated sample using a Vickers indentation tester (HVS-1000) (20 points or more per sample), with a load of 100g and a retention time of 10 s.
The results of the modification depth and hardness test are shown in table 1.
TABLE 1-test results of examples 1 to 6 and comparative example
Fig. 1, 4, 7, 10, 13 and 16 are graphs comparing the hardness of the substrate and the coated substrate of examples 1 to 6, respectively, and it can be seen from the hardness of examples 1 to 6 in fig. 1, 4, 7, 10, 13 and 16 and table 1 that the coating layer is clad on the surface of the substrate, the surface hardness of the coating layer is remarkably increased relative to the hardness of the substrate, and it can be seen that the coating layer has high hardness on the surface of the substrate, and the hardness of the substrate surface is improved.
Fig. 2, 5, 8, 11, 14, and 17 are ECC plots of the surfaces of the coated substrates of examples 1-6, respectively, and fig. 3, 6, 9, 12, 15, and 18 are plots of EDS surface scan results of the second phase in the coatings of examples 1-6, respectively. It can be seen from fig. 2, 5, 8, 11, 14 and 17 that a large number of finely dispersed white spherical second phase particles are dispersed in the coating.
Through the EDS test, it can be seen from fig. 3, fig. 6, fig. 9, fig. 12, fig. 15 and fig. 18 that segregation of Al and O elements occurs in the second phase particles in the coatings of examples 1-6, and the distribution of elements in the surrounding coating structure is relatively uniform. As can be seen from fig. 2, 5, 8, 11, 14 and 17, it can be determined that the second phase dispersed in the coating is Al2O3The atomic size difference between the particles of the second phase and the surrounding coating tissue can cause serious lattice distortion, effectively block dislocation movement and generate obvious hardening effect.
In addition, in the case of comparing example 1 with example 3 and example 5, it is seen from table 1 that the coating hardness ratio of the coating raw material added with Fe, Cr and Ni elements is pure Al as the raw material, because of the difference in the coating raw material composition, although the cladding conditions are the same2O3The hardness increase of the coating is more pronounced, as can also be seen from the comparative data of example 2, example 4 and example 5.
As can be seen from FIGS. 1, 3, 5, 7, 9 and 11, the starting material in examples 1-2 is Al alone2O3The coating mainly consists of thicker massive delta ferrite, while the coating of the raw materials of the examples 3-6, which are added with Fe, Cr and Ni elements, mainly consists of fine lath martensite, and the average grain size of the coating of the examples 3-6 is obviously smaller, which necessarily produces more remarkable fine grain strengthening effect. From this, fine grain strengthening andthe two-phase strengthening has a combined effect of making the hardness of the coating higher by adding Fe, Cr and Ni elements to the raw material.
Comparing examples 3 and 5, or examples 4 and 6, it can be seen from Table 1 that Al is a raw material for coating2O3The mass ratio of Fe, Cr and Ni elements is 17.1: 68.4: 9.5: and 5, the hardness of the coating substrate is optimal.
The same coating materials were used in examples 1-2, examples 3-4, and examples 5-6, and it is understood from Table 1 that the hardness obtained differs depending on the laser power and the laser modification depth, and that the hardness is higher as the laser modification depth is higher in the range of 50-100W of laser power.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.