A self-lubricating cemented carbide coating and its preparation process

Abstract

The present invention relates to the field of metal materials, and particularly to a self-lubricating cemented carbide coating and its preparation process. The present invention discloses a self-lubricating cemented carbide coating, the composition of which includes an alloy coating provided on the surface of steel, comprising the following elements in mass percentage content (Wt / %): WC: 20 - 30%, TiC: 0 - 10%, Co: 1 - 5%, Ni: 10 - 14%, Cr: 1 - 5%, and the balance is Cr3C2. For the self-lubricating cemented carbide coating of the present invention, inexpensive carbides Cr3C2 and TiC are used to partially replace WC, and inexpensive binder phase Ni is used to partially replace Co. While ensuring the performance, the raw material cost price is reduced, thereby reducing its production cost as a whole and making large-scale application possible; a self-lubricating phase is added, and by improving the ratio, the friction coefficient is reduced, and the wear-resistant and anti-friction performance of the cemented carbide coating is improved.

Description

Technical Field

[0001] The present invention relates to the field of metal materials, and particularly to a self-lubricating cemented carbide coating and a preparation process thereof. Background Art

[0002] Cemented carbide is a metal-ceramic material prepared by powder metallurgy from micron-sized high-hardness and difficult-to-melt carbides such as tungsten carbide (WC), titanium carbide (TiC), and chromium carbide (Cr3C2), transition metal cobalt (Co), nickel (Ni), and other trace element powders. It is also often used as a coating in surface engineering and has been widely used in many fields due to its good performance. The application of cemented carbide coatings in the field of material surfaces has doubled the wear resistance, corrosion resistance, and other properties of the substrate material, greatly reducing the production cost and improving the production efficiency. In the process of preparing WC cemented carbide coatings, the HVOF spraying method has great advantages over other spraying methods in terms of both working efficiency and coating quality, and is currently the main method for preparing WC-based coatings.

[0003] The WC cemented carbide coating prepared by the HVOF spraying method has the characteristics of good wear resistance and corrosion resistance, and has successfully replaced the electroplated hard chromium process in many fields such as aviation and machinery. However, it also has defects such as large gas consumption, high powder price, low deposition rate during spraying, and high post-processing costs due to the high hardness of the coating, resulting in a high price for the HVOF sprayed WC coating. This makes it difficult to widely apply the HVOF sprayed WC coating. Currently, the research on WC coatings mainly focuses on improving the coating performance, and rarely considers how to reduce the preparation cost of alternative coatings while meeting the usage requirements.

[0004] Based on the characteristics of WC cemented carbide coatings, wear is a very common problem, almost involving all movement processes of mechanical components. Failure and replacement due to wear have greatly reduced the service life and production operation efficiency of components. WC coatings have a large number of applications in the industrial field due to their excellent wear resistance. The hard phase WC particles increase the average hardness, and the binder phases such as Co, Ni, and Cr connect the carbide particles to improve the toughness of the material. The friction and wear performance of wear-resistant coatings such as WC-Co and WC-Co-Cr obtained by combining the hard phase and the binder phase is affected by factors such as powder type, mechanical properties of the coating, microstructure, spraying process, and wear conditions on the one hand. On the other hand, because different working conditions are faced in actual applications and different types of wear are experienced. Usually, the wear types during the mechanical wear process of coatings are divided into corrosive wear, abrasive wear, erosive wear, fatigue wear, adhesive wear, etc. In reality, wear is often the result of the idealized action of two or more wear types. Summary of the Invention

[0005] In view of this, the present invention is expected to provide a self-lubricating cemented carbide coating and its preparation process, which uses inexpensive carbides Cr3C2 and TiC to partially replace WC, and inexpensive binder phase Ni to partially replace Co. While ensuring performance, it realizes a reduction in the raw material cost price, thereby reducing its production cost as a whole and making large-scale application possible.

[0006] The technical solution of the embodiment of the present invention is realized as follows:

[0007] A self-lubricating cemented carbide coating, characterized in that: its composition includes an alloy coating provided on the surface of the steel, including the following elements in mass percentage content (Wt / %): WC: 20 - 30%, TiC: 0 - 10%, Co: 1 - 5%, Ni: 10 - 14%, Cr: 1 - 5%, and the balance is Cr3C2.

[0008] The above alloy coating includes a cemented carbide phase and a cobalt-chromium-nickel binder phase, and the cobalt-chromium-nickel binder phase surrounds the cemented carbide phase in a network.

[0009] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 20%, Co: 1%, Ni: 10%, Cr: 5%, and the balance is Cr3C2.

[0010] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 25%, Co: 3%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0011] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 25%, TiC: 10%, Co: 1%, Ni: 12%, Cr: 5%, and the balance is Cr3C2.

[0012] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 30%, TiC: 5%, Co: 1%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0013] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 20%, Co: 1%, Ni: 14%, and the balance is Cr3C2.

[0014] The above alloy coating includes the following elements in mass percentage content (Wt / %): WC: 20%, h-BN: 1 - 3%, Co: 1%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0015] On the other hand, a preparation process of a self-lubricating cemented carbide coating includes the following steps: preparing materials according to the elemental composition of the self-lubricating cemented carbide coating, mixing each raw material, and obtaining a spraying powder through spray granulation; spraying the spraying powder by supersonic flame to obtain the coating.

[0016] Spraying is carried out by supersonic flame, and the process parameters are: air flow rate 104 psi, propane flow rate 97 psi, spraying distance 180 mm - 220 mm, powder feeding efficiency 7.4.

[0017] In the above preparation process, spraying is carried out by supersonic flame, and the process parameters are: air flow rate 107 psi, propane flow rate 91 psi, spraying distance 220 mm, powder feeding efficiency 7.4.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a self-lubricating cemented carbide coating, which uses inexpensive carbides Cr3C2 and TiC to partially replace WC, and inexpensive binder phase Ni to partially replace Co. While ensuring performance, it realizes a reduction in the raw material cost price, thereby reducing its production cost as a whole and making large-scale application possible; moreover, by adding a self-lubricating phase and exploring its optimal addition ratio, the friction coefficient is reduced, and the wear-resistant and friction-reducing performance of the cemented carbide coating is improved. At the same time, the present invention provides the best preparation process for the self-lubricating cemented carbide coating to obtain a coating with the highest spraying efficiency and the best performance. Brief Description of the Drawings

[0020] The present invention will be further described below in conjunction with the drawings and embodiments.

[0021] Figure 1 It is the cross-sectional image of the cemented carbide coating described in Embodiment 1 of the present invention under a 5KX scanning electron microscope (scale bar is 2 μm);

[0022] Figure 2 It is the cross-sectional image of the cemented carbide coating described in Embodiment 2 of the present invention under a 5KX scanning electron microscope (scale bar is 2 μm);

[0023] Figure 3 It is the cross-sectional image of the cemented carbide coating described in Embodiment 3 of the present invention under a 5KX scanning electron microscope (scale bar is 2 μm);

[0024] Figure 4 It is the cross-sectional image of the cemented carbide coating described in Embodiment 4 of the present invention under a 5KX scanning electron microscope (scale bar is 2 μm);

[0025] Figure 5 It is the cross-sectional image of the cemented carbide coating described in Embodiment 5 of the present invention under a 5KX scanning electron microscope (scale bar is 1 μm);

[0026] Figure 6 Cross-sectional image of the cemented carbide coating described in Example 6 of the present invention under a 5KX scanning electron microscope (scale bar is 3μm);

[0027] Figure 7 Cross-sectional image of the cemented carbide coating described in Example 7 of the present invention under a 5KX scanning electron microscope (scale bar is 2μm);

[0028] Figure 8 Cross-sectional image of the cemented carbide coating described in Example 8 of the present invention under a 5KX scanning electron microscope (scale bar is 2μm);

[0029] Figure 9 Cross-sectional image of the cemented carbide coating described in Example 9 of the present invention under a 5KX scanning electron microscope (scale bar is 2μm);

[0030] Figure 10 is Figure 5 Energy spectrum analysis of the coating points at positions 1, 2, 3, and 4 in (scale bar is 1μm);

[0031] Figure 11A Morphology image of the cemented carbide coating described in Example 1 of the present invention under a 500X electron microscope after a friction and wear experiment (scale bar is 20μm);

[0032] Figure 11B Morphology image of the cemented carbide coating described in Example 1 of the present invention under a 5KX electron microscope after a friction and wear experiment (scale bar is 2μm);

[0033] Figure 12A Morphology image of the cemented carbide coating described in Example 2 of the present invention under a 500X electron microscope after a friction and wear experiment (scale bar is 100μm);

[0034] Figure 12B Morphology image of the cemented carbide coating described in Example 2 of the present invention under a 5KX electron microscope after a friction and wear experiment (scale bar is 2μm);

[0035] Figure 13A Morphology image of the cemented carbide coating described in Example 3 of the present invention under a 500X electron microscope after a friction and wear experiment (scale bar is 20μm);

[0036] Figure 13B Morphology image of the cemented carbide coating described in Example 3 of the present invention under a 5KX electron microscope after a friction and wear experiment (scale bar is 2μm);

[0037] Figure 14AMorphology diagram of the cemented carbide coating described in Embodiment 4 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 20 μm);

[0038] Figure 14B Morphology diagram of the cemented carbide coating described in Embodiment 4 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2 μm);

[0039] Figure 15A Morphology diagram of the cemented carbide coating described in Embodiment 5 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 100 μm);

[0040] Figure 15B Morphology diagram of the cemented carbide coating described in Embodiment 5 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2 μm);

[0041] Figure 16A Morphology diagram of the cemented carbide coating described in Embodiment 6 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 20 μm);

[0042] Figure 16B Morphology diagram of the cemented carbide coating described in Embodiment 6 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2 μm);

[0043] Figure 17A Morphology diagram of the cemented carbide coating described in Embodiment 7 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 20 μm);

[0044] Figure 17B Morphology diagram of the cemented carbide coating described in Embodiment 7 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2 μm);

[0045] Figure 18A Morphology diagram of the cemented carbide coating described in Embodiment 8 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 20 μm);

[0046] Figure 18B Morphology diagram of the cemented carbide coating described in Embodiment 8 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2 μm);

[0047] Figure 19A Morphology diagram of the cemented carbide coating described in Embodiment 9 of the present invention under a 500X electron microscope after friction and wear experiments (scale bar is 20 μm);

[0048] Figure 19BMorphology diagram of the cemented carbide coating described in Embodiment 9 of the present invention under a 5KX electron microscope after friction and wear experiments (scale bar is 2μm);

[0049] Figure 20 Morphology diagrams and partial enlarged diagrams of s-1 coating, s-2 coating and s-3 coating under a 500X electron microscope (scale bar of the morphology diagram is 10μm);

[0050] Figures 21 - 23 Porosity images of s-1 coating, s-2 coating and s-3 coating respectively after being processed by ImageJ software;

[0051] Figure 24 Friction coefficient real-time curve of the self-lubricating coating;

[0052] Figure 25 Polarization curve of the self-lubricating coating. Specific implementation manners

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0054] The selection of powder raw materials is mainly to reduce costs on the premise of meeting performance requirements. The principle of the present invention is that in the selection of hard phases, Ni is partially substituted for Co, and TiC and Cr3C2 are partially substituted for WC, and a new coating system of WC-Cr3C2-TiC-Co-Ni-Cr system is designed. Based on the principle mentioned above, the present invention provides a self-lubricating cemented carbide coating. Different from the prior art, the self-lubricating cemented carbide coating provided by the present invention comprises an alloy coating disposed on the surface of steel, including the following elements in mass percentage content (Wt / %): WC: 20-30%, TiC: 0-10%, Co: 1-5%, Ni: 10-14%, Cr: 1-5%, and the balance is Cr3C2.

[0055] Preferably, the self-lubricating cemented carbide coating includes the following elements in mass percentage content (Wt / %): WC: 20%, h-BN: 1-3%, Co: 1%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0056] Among them, h-BN is hexagonal boron nitride, which has lubricity in a relatively wide temperature range.

[0057] Specifically, a self-lubricating cemented carbide coating proposed by the present invention, its composition includes an alloy coating disposed on the surface of steel, including the following elements in mass percentage content (Wt / %), and the composition components of specific examples and comparative examples are as shown in Table 1 below:

[0058]

[0059] On the other hand, a preparation process of a self-lubricating cemented carbide coating includes the following steps: preparing materials according to the elemental composition of the self-lubricating cemented carbide coating, mixing the respective raw materials, followed by ball milling, spray granulation, high-temperature sintering, and supersonic flame spraying; obtaining spraying powder through spray granulation; and spraying the spraying powder through supersonic flame to obtain the coating.

[0060] Among them, the process parameters for spray granulation are shown in Table 2 below:

[0061]

[0062] The process parameters for high-temperature sintering are: sintering in a molybdenum wire furnace at 1120 °C.

[0063] For supersonic flame spraying, the process parameters are: air flow rate 104 psi, propane flow rate 97 psi, spraying distance 180 mm - 220 mm, and powder feeding efficiency 7.4.

[0064] Preferably, for supersonic flame spraying, the process parameters are: air flow rate 107 psi, propane flow rate 91 psi, spraying distance 220 mm, and powder feeding efficiency 7.4.

[0065] Example 1:

[0066] The self-lubricating cemented carbide coating includes the following elements in mass percentage content (Wt / %): WC: 20%, TiC: 0%, Co: 1%, Ni: 10%, Cr: 5%, and the balance is Cr3C2.

[0067] The specific process of preparing the self-lubricating cemented carbide coating is as follows: preparing materials according to the elemental composition of the self-lubricating cemented carbide coating, mixing the respective raw materials, followed by ball milling, spray granulation, high-temperature sintering, and supersonic flame spraying; obtaining spraying powder through spray granulation; and spraying the spraying powder through supersonic flame to obtain the coating.

[0068] Among them, the process parameters for spray granulation are as shown in Table 2 above:

[0069] The process parameters for high-temperature sintering are: sintering in a molybdenum wire furnace at 1120 °C.

[0070] For supersonic flame spraying, the process parameters are: air flow rate 107 psi, propane flow rate 91 psi, spraying distance 220 mm, and powder feeding efficiency 7.4.

[0071] For the prepared self-lubricating cemented carbide coating, performance testing is carried out, and the results are as described in Table 3 below:

[0072]

[0073] Example 2:

[0074] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 20%, TiC: 5%, Co: 3%, Ni: 12%, Cr: 5%, and the balance is Cr3C2.

[0075] The preparation process is the same as that of Example 1. The performance of the prepared self-lubricating cemented carbide coating is detected, and the results are as shown in Table 4 below:

[0076]

[0077] Example 3:

[0078] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 20%, TiC: 10%, Co: 5%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0079] The preparation process is the same as that of Example 1. The performance of the prepared self-lubricating cemented carbide coating is detected, and the results are as shown in Table 5 below:

[0080]

[0081] Example 4:

[0082] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 25%, TiC: 0%, Co: 3%, Ni: 14%, Cr: 5%, and the balance is Cr3C2.

[0083] The preparation process is the same as that of Example 1. The performance of the prepared self-lubricating cemented carbide coating is detected, and the results are as shown in Table 6 below:

[0084]

[0085] Example 5:

[0086] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 25%, TiC: 5%, Co: 5%, Ni: 10%, Cr: 5%, and the balance is Cr3C2.

[0087] The preparation process is the same as that of Example 1. The performance of the prepared self-lubricating cemented carbide coating is detected, and the results are as shown in Table 7 below:

[0088]

[0089] Example 6:

[0090] Self-lubricating cemented carbide coating, including the following elements in weight percentage (Wt / %): WC: 25%, TiC: 10%, Co: 1%, Ni: 12%, Cr: 5%, and the balance is Cr3C2. The preparation process is the same as that of Example 1. The prepared self-lubricating cemented carbide coating is subjected to performance testing, and the results are as described in Table 8 below:

[0091]

[0092] Example 7:

[0093] Self-lubricating cemented carbide coating, including the following elements in weight percentage (Wt / %): WC: 30%, TiC: 0%, Co: 5%, Ni: 12%, Cr: 5%, and the balance is Cr3C2. The preparation process is the same as that of Example 1. The prepared self-lubricating cemented carbide coating is subjected to performance testing, and the results are as described in Table 9 below:

[0094]

[0095] Example 8:

[0096] Self-lubricating cemented carbide coating, including the following elements in weight percentage (Wt / %): WC: 30%, TiC: 5%, Co: 1%, Ni: 14%, Cr: 5%, and the balance is Cr3C2. The preparation process is the same as that of Example 1. The prepared self-lubricating cemented carbide coating is subjected to performance testing, and the results are as described in Table 10 below:

[0097]

[0098] Example 9:

[0099] Self-lubricating cemented carbide coating, including the following elements in weight percentage (Wt / %): WC: 30%, TiC: 10%, Co: 3%, Ni: 10%, Cr: 5%, and the balance is Cr3C2. The preparation process is the same as that of Example 1. The prepared self-lubricating cemented carbide coating is subjected to performance testing, and the results are as described in Table 11 below:

[0100]

[0101] Figures 1 - 9 For the cross-sectional images of the coatings of Examples 1-9 under a 5KX scanning electron microscope, it can be found that there are mainly four position regions: light gray, dark gray, white, and black. From Figure 5 , the cross-sectional image of the coating of Example 5 under a 5KX scanning electron microscope, and Figure 10The energy spectrum analysis of Example 5 shown in the figure shows that the light gray position (position 1) has a high distribution of Co, Cr, Ni and other binder phases, and surrounds other phases in a network shape, and is distributed in the interphases of other colors, indicating that this position is mainly the area where the binder phase is distributed. The dark gray position (position 2) with a large block distribution has a very high content of Cr and W elements, indicating that this position is mainly composed of Cr carbides Cr3C2, Cr7C3 and Cr 23 C6. The white position (position 3) has more W elements, indicating that this position is a hard phase WC with a polygonal distribution. The black position (position 4) energy spectrum shows that there is a large distribution of Ti elements, which can be determined to be a hard phase TiC.

[0102] Specifically in Figure 10 In the spectrum analysis, the horizontal axis is the energy axis, the unit is kiloelectron volts (KeV); the vertical axis is the intensity axis, which represents the intensity of X-ray photons, the unit is pulse counts (counts);

[0103] At room temperature, the wear resistance of each group of coatings is tested by sliding friction method. By studying the wear mechanism and wear conditions, the coating component with the best wear resistance is determined. The friction coefficient can reflect the friction performance of the coating to a certain extent. The smaller the friction coefficient, the better the wear resistance, and vice versa.

[0104] After the friction and wear experiment, the wear scar morphology was observed using a scanning electron microscope. Figures 11A - 19B The wear scar morphology of the coating of Example 1-Example 9 under a 500X electron microscope (magnification 500 times) and a 5KX electron microscope (magnification 5000 times) can be seen from the morphology. It can be seen that there is flaking and curling at the wear scar. The flaking phenomenon is mainly caused by fatigue wear. During the wear process, the coating is subjected to the shear force, and the shear deformation accumulates a large amount of dislocation accumulation on the coating surface to form cracks. When the cracks accumulate to a certain extent and reach the critical point, the coating surface will flak off. Under a 5KX electron microscope, a large number of lumpy coatings that have fallen off and coatings that are about to fall off, as well as a large number of cracks can be seen in the morphology of the wear scar magnified 5000 times. And the cracks occur at the junction of the dark gray hard phase and the light gray bonding phase around it, and first occur on the bonding phase. A large amount of bonding phase is pulled out to form wear debris, which is also reflected in the electron microscope photos. When the bonding phase is severely damaged, the large hard phase particles will lose support and eventually be pulled out, causing coating damage. This shows that the staggered distribution state of the hard phase and the bonding phase and the combination of the two are particularly important for the friction resistance of the coating, and the porosity in the hard phase and the bonding phase in the coating has an important influence on its wear resistance.

[0105] In the coating morphology diagrams of Example 2, Example 3, Example 5, Example 6, Example 7, and Example 8, it can be seen that the surface coating is rolled up. This is mainly because during the friction process, the hard phase in the coating interacts with the counter ball, resulting in a cutting effect on the coating and plastic deformation. The scratching action of the wear debris forms scratches on the coating surface and causes the shedding of the surface coating. The main mechanism of this coating wear is abrasive wear.

[0106] In addition, abrasive accumulation occurs at the edges of the wear marks of each coating. The height on both sides of the edge of the scratch is higher than that in the middle of the wear mark. This is mainly because during the friction process, the friction pair continuously pushes the wear debris, which eventually accumulates at the edge of the wear mark, forming abrasive accumulation.

[0107] Among them, in this application, for the hardness test of the coating, a microhardness tester is used to measure the substrate and the coating cross-section in sequence. In all specimens, 15 points are selected at equal intervals on the surface and cross-section, recorded, and the data is summarized. The average value is taken as the measurement result.

[0108] For the test of the coating porosity, image analysis is used to measure the porosity. The ImagePro-Plus software is used to identify and statistically calculate the porosity of the coating cross-section.

[0109] For the friction and wear experiment, a high-temperature friction and wear testing machine is used to investigate the wear resistance of the coating. After the friction and wear test, SEM is used to observe the wear and friction of the coating, and the possible wear mechanism is inferred from the secondary electron scanning images taken. Then, a LEXTOLS4000 type laser confocal microscope produced by Olympus is used to measure the friction track to obtain a two-dimensional scratch profile and a three-dimensional wear mark diagram.

[0110] For the coating corrosion resistance test, the test method of tensile bonding specimens is selected and tested according to the ASTM C633-01 standard.

[0111] Comparative Example 1

[0112] The self-lubricating cemented carbide coating includes the following elements in mass percentage (Wt / %): WC: 25%, TiC: 0%, Co: 20%, Ni: 0%, Cr: 0%, and the balance is Cr3C2.

[0113] The preparation process is the same as that of Example 1. For the prepared self-lubricating cemented carbide coating, the average wear rate and average friction coefficient are tested. The results are: the average wear rate is 12.5*10 -9 mm 3 ·N -1 ·m -1 , and the average friction coefficient is 0.54.

[0114] Comparative Example 2

[0115] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 25%, TiC: 0%, Co: 0%, Ni: 20%, Cr: 0%, and the balance is Cr3C2.

[0116] The preparation process is the same as that of Example 1. For the obtained self-lubricating cemented carbide coating, the average wear rate and average friction coefficient are tested. The results are: the average wear rate is 13.8×10 -9 mm 3 ·N -1 ·m -1 , and the average friction coefficient is 0.53.

[0117] Comparative Example 3

[0118] The self-lubricating cemented carbide coating comprises the following elements in weight percentage (Wt / %): WC: 25%, TiC: 0%, Co: 0%, Ni: 0%, Cr: 20%, and the balance is Cr3C2.

[0119] The preparation process is the same as that of Example 1. For the obtained self-lubricating cemented carbide coating, the average wear rate and average friction coefficient are tested. The results are: the average wear rate is 14.7×10 -9 mm 3 ·N -1 ·m -1 , and the average friction coefficient is 0.56.

[0120] After the friction and wear experiment, based on the wear volume, the experimental analysis is carried out to find the best formula. As shown in Table 13, according to the experimental results of the orthogonal experiment with 4 factors and 3 levels, the best coating composition formula is explored. In Table 12, A, B, C, and D respectively represent WC, TiC, Co, and Ni, and 1, 2, and 3 respectively represent the corresponding composition levels of WC, TiC, Co, and Ni.

[0121]

[0122]

[0123] First, we calculated the sum of the average wear rates of each factor (A, B, C, D) at three different levels, denoted as K1, K2, and K3 respectively. Through comparison and calculation, considering only the average wear rate, the minimum arithmetic mean of A corresponds to level 1, the minimum arithmetic mean of B corresponds to level 1, the minimum arithmetic mean of C corresponds to level 1, and the minimum arithmetic mean of D corresponds to level 3. Therefore, the best wear-resistant component combination is A1B1C1D3, and the ratio of the best components is shown in Table 14. Since there is no such formula ratio in the experimental group, verification tests need to be carried out to verify the results.

[0124]

[0125] According to Table 14, the composition of the best coating with an average wear rate after orthogonal analysis is 20WC - 59Cr3C2 - Co - 5Cr - 14Ni. Prepare the coating (verification group) according to this coating formula, and test its various properties as shown in Table 15 below;

[0126]

[0127] It can be seen that the average friction coefficient of the verification group is 0.42. The average wear area of the cross-section of the verification group is 1113.38μm 2 , which is less than 1160.08μm of the coating of Example 1 with the smallest cross-sectional average wear area in the experimental group 2 . The wear rate of the verification group is 1.84×10 -9 mm 3 ·N -1 ·m -1 , which is less than 1.92×10 -9 mm 3 ·N -1 ·m -1 of the coating of Example 1 with the smallest wear rate in the experimental group, and the wear rate has decreased by 4.20% compared with the coating of Example 1.

[0128] Example 10

[0129] For the self-lubricating cemented carbide coating, the h-BN phase is selected as the self-lubricating phase, listed as s-1 coating, s-2 coating, and s-3 coating; among them, 1%, 2%, and 3% are doped into the cemented carbide coating for the s-1 coating, s-2 coating, and s-3 coating respectively to improve the wear resistance of the coating. The preparation processes of the s-1 coating, s-2 coating, and s-3 coating are the same as those of Example 1;

[0130] The raw material ratios of the s-1 coating, s-2 coating, and s-3 coating are shown in Table 16 below:

[0131]

[0132] Figure 20 They are the SEM morphology images and partial enlarged images of the s-1 coating, s-2 coating, and s-3 coating at 1000 times magnification. It can be found that obvious defects such as pores and cracks can be seen in both the 1000-fold magnification morphology image and the partial enlarged image, especially more obvious in the morphology image of the s-3 coating. And it can be found that pores and cracks are generally located at the junction of the hard phase and the binder phase, which will have an adverse impact on the hardness, toughness, wear resistance, and corrosion resistance of the coating.

[0133] Figures 21 - 23 They are the porosity images of the s-1 coating, s-2 coating, and s-3 coating after being processed by ImageJ software. From the distribution of the porosity of the self-lubricating coating, the porosity of the s-1 coating is the lowest, which is 0.25%, being at a relatively low level compared to the coating without adding the self-lubricating phase. The porosity of the s-2 coating increases to 0.55%, while the porosity of the s-3 coating increases significantly to 1.55%, being at a relatively high level compared to the coating without adding the self-lubricating phase. It verifies that the doping of h-BN has an important impact on the denseness of the coating, and with the increase of the content of the lubricating phase, the porosity of the coating will also increase.

[0134] Regarding the microhardness of the coating, the microhardness of the s-1 coating is 1163.12 HV, which is greater than 1110.67 HV of the coating without the lubricating phase for verification. However, the microhardness of the s-2 coating shows a decrease to varying degrees compared to the s-1 coating and s-3 coating. This is mainly because the s-2 coating and s-3 coating have more porosity, which affects the microhardness of the coating.

[0135] Figure 24 It is the real-time curve of the friction coefficient of the self-lubricating coating. The abscissa is time, with the unit of min, and the ordinate is the friction coefficient. From the real-time curve of the friction coefficient of the self-lubricating coating, it can be seen that its fluctuation trend is consistent with the law of the friction coefficient in the previous experiment. When friction occurs, the friction coefficient rapidly increases to a certain order of magnitude, then has a small drop, continues to fluctuate for about 5 minutes, and then fluctuates slightly within a certain range. It can be seen from the real-time curve that the friction coefficient of the s-1 coating is the largest, the s-3 coating is the second, and the s-2 coating is the smallest. From the average friction coefficient, the s-1 coating is 0.32, the s-2 coating is 0.27, and the s-3 coating is 0.29. Compared with the average friction coefficient range of the coating without the lubricating phase being between 0.30 - 0.61, the lubricating phase will reduce the friction coefficient to a certain extent. The average wear area of the cross-section of the s-3 coating is 1299.21 μm 2 , and the wear rate is 2.03 * 10 -9 mm 3 ·N -1 ·m -1The average cross-sectional wear area of the s-2 coating is 890.29 μm 2 , and the wear rate is 1.47×10 - 9 mm 3 ·N -1 ·m -1 The average cross-sectional wear area of the s-1 coating is 1025.69 μm 2 , and the wear rate is 1.69×10 -9 mm 3 ·N -1 ·m -1 The wear rate of the s-2 coating decreased by 20.10% compared with the non-lubricating phase verification coating, and the wear rate of the s-2 coating decreased by 8.15% compared with the non-lubricating phase verification coating. The wear rate of the s-3 coating increased slightly compared with the non-lubricating phase verification coating.

[0136] Figure 25 The polarization curve of the self-lubricating coating, the abscissa is the current, the unit is A, and the ordinate is the voltage, the unit is V; the self-corrosion potential of the s-1 coating is -0.54 V, and the corrosion current density is 1.73 μA·cm -2 , the self-corrosion potential of the s-2 coating is -0.48 V, and the corrosion current density is 1.86 μA·cm -2 , the self-corrosion potential of the s-3 coating is -0.71 V, and the corrosion current density is 5.25 μA·cm -2 The corrosion current density of the s-3 coating is the largest, mainly because it has more pores and cracks.

[0137] (1) The doping of h-BN will have an adverse effect on the densification of the coating. As the doping ratio increases, the porosity and cracks in the coating will increase.

[0138] (2) The reason why the self-lubricating phase can reduce the friction coefficient and wear rate is that it can form a lubricating film between the friction pair and the coating surface, so that the wear process can only exist in the form of abrasive wear, greatly reducing the friction coefficient and wear rate.

[0139] (3) Due to the high melting point of h-BN, after being burned by the high temperature of supersonic flame spraying, h-BN can still partially exist in the sprayed coating.

[0140] (4) The h-BN doped with 2% has the lowest wear rate, the average cross-sectional wear area is 890.29 μm 2 , and the wear rate is 1.47×10 -9 mm 3 ·N -1 ·m -1 , and the wear rate of the coating decreased by 20.10% compared with the non-lubricating phase verification coating.

[0141] The present invention optimizes process parameters through orthogonal experiments, selects the best process parameters under different criteria, and conducts verification tests on the process parameters with the best comprehensive score. The verification experiments prove that the coating has better performance under the process parameters of this application. The relevant summary is as follows:

[0142] (1) The order of the influence of process parameters on the score is: air flow rate > propane pressure > spraying distance > powder feeding efficiency. The order of the influence of process parameters on the particle temperature is: propane > air > spraying distance > powder feeding efficiency. The order of the influence of process parameters on the particle velocity is: spraying distance > air > powder feeding efficiency > propane.

[0143] (2) Taking the comprehensive score as the main evaluation criterion, the best process parameters are: air flow rate 104 psi, propane flow rate 97 psi, spraying distance 220 mm, and powder feeding efficiency 7.4. Taking the particle temperature score as the main evaluation criterion, the best process parameters are: air flow rate 104 psi, propane flow rate 97 psi, spraying distance 180 mm, and powder feeding efficiency 7.4. Taking the particle velocity score as the main evaluation criterion, the best process parameters are: air flow rate 107 psi, propane flow rate 91 psi, spraying distance 220 mm, and powder feeding efficiency 7.4.

[0144] (3) Under the preparation process of this application, taking the score as the main evaluation criterion, the score calculated from the particle temperature and velocity is 832.70, which is greater than the maximum of 824.57 in the orthogonal experiment. Taking the particle temperature as the main evaluation criterion, the measured particle temperature is 1500 °C, which is greater than the maximum of 1470 °C in the orthogonal experiment. When taking the particle velocity as the main evaluation criterion, the measured particle velocity is 1021 m / s, which is also greater than the maximum particle velocity of 1000 m / s in the orthogonal experiment.

[0145] (4) In the verification test of the process parameters with the best score, the coating has very good densification, and the porosity is only 0.11%, which is reduced by 47.61%.

[0146] (5) The hardness of the coating verified by the process parameters has also increased slightly. Compared with the highest hardness without parameter optimization, it reaches 1192.63 HV, an increase of 2.54%.

[0147] (6) The average friction coefficient of the coating verified by the process is 0.25, which is reduced by 7.40%. The average wear area of the cross-section is 792.56 μm 2 , and the wear rate is 1.31×10 -9 mm 3 ·N -1 ·m -1, compared with the wear rate of the s-2 coating without parameter optimization, which is 1.47*10 -9 mm 3 ·N -1 ·m -1 , the wear rate has decreased by 10.75%.

[0148] (7) The self-corrosion potential of the coating verified by process parameters is -0.46V, and the corrosion current density is 0.72 μA·cm -2 . Compared with the minimum of 0.90 μA·cm in the coating without process optimization -2 , it has decreased by 20.00%.

[0149] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims described above.

Claims

1. A self-lubricating cemented carbide coating, characterized in that: Its composition includes an alloy coating arranged on the surface of a steel material, wherein the alloy coating includes a hard alloy phase and a cobalt-chromium-nickel bonding phase, and the cobalt-chromium-nickel bonding phase surrounds the hard alloy phase in a network shape; the alloy coating includes the following elements in percentage by mass: WC: 20%, h-BN: 2%, Co: 1%, Ni: 14%, Cr: 5%, and the remainder is Cr3C2.

Images