A steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a shale mining cutter

Abstract

The present application relates to a kind of steel bonding hard alloy ball particle reinforced hard surface coating applied to mudstone mining cutter protection, belong to the technical field of special coating design preparation.The coating is prepared by the following steps: (1) high-temperature spheroidization steel bonding hard alloy ball particle;High-temperature spheroidization process parameters are as follows: gap voltage is 45V-55V, discharge current is 500A, pulse width 2000 μs, pulse interval 200 μs, electrode rotating speed 3000 r / min;(2) hard surface coating;Its operation is that after the surface of steel base is polished and rusted, it is ultrasonically cleaned in acetone and anhydrous ethanol, surface grease is removed and dried, and laser cladding process parameters are as follows: laser power 1400W, scanning speed is 600mm / min, powder feeding rate is 1r / min, and lap spacing is 48%.The hardness of the coating obtained by the present application can be 61.5-61.9HRC, and the volume wear rate is less than or equal to 8.28×10 ‑7 mm 3 / N·m.The preparation process of the present application is simple and controllable, and the performance of the obtained product is far superior to that of the same product in the prior art, and is convenient for industrial application.

Description

TECHNICAL FIELD

[0001] The application relates to a steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a mudstone mining cutter, and belongs to the technical field of special coating design and preparation. BACKGROUND

[0002] Mudstone strata contain a large number of fine mineral particles (particle size less than 0.0039 mm), such as quartz, mica and silicon dioxide. When a shield machine excavates in the strata, cutter wear is prone to occur due to abrasive wear. In order to realize high-efficiency tunneling of the mudstone strata, the cutters such as the rolling cutter, the tearing cutter and the side cutter need to have high hardness and high wear resistance. The existing forged high-strength alloy steel with surface carburizing cannot meet the requirements, and therefore, a wear-resistant coating needs to be prepared on the surface of the shield cutter by using surface technology.

[0003] Traditional hard surface materials (represented by Co-based and Ni-based self-fluxing alloy binder phase + WC reinforcing phase) are often used for cutter surface protection due to corrosion resistance, wear resistance and impact resistance. Taking the Ni60+WC system as an example, the reinforcing phase of the existing coating is mostly large-particle cast tungsten carbide, and the difference between the thermal expansion coefficients of the large-particle WC and the Ni60 is large, which easily accumulates thermal stress and produces cracks in the laser cladding process, which seriously limits the content of the reinforcing phase in the coating and affects the wear resistance of the coating.

[0004] In addition, in the laser cladding process, the specific gravities of the large-particle reinforcing phase and the binder phase are inconsistent, which easily leads to uneven powder feeding and affects the deposition rate of the reinforcing phase. Specifically, 1) in the powder feeding process, the high-specific-gravity reinforcing phase (such as WC) has a serious lag phenomenon; and 2) the low-specific-gravity reinforcing phase (such as TiC) is easily scattered due to the backwash effect when being transported to the substrate by the carrier gas, which will limit the content of the reinforcing phase entering the molten pool. This is one of the main reasons why laser cladding is rarely used to prepare steel-bonded hard alloy with a reinforcing phase content greater than 55V% so far. SUMMARY

[0005] The application designs and first uses laser cladding technology to prepare a composite hard surface coating rich in steel-bonded hard alloy ball particles.

[0006] The application improves the structural stability of the existing mudstone mining cutter coating, further improves the wear resistance of the coating, and prolongs the service life of the cutter. Meanwhile, the cost of the application is significantly lower than that of the prior art.

[0007] The application takes high-temperature spheroidized steel binder ball as raw material, and prepares high-performance hard surface coating through improved laser cladding technology. Small size strengthening phase will experience the process of "dissolution-reprecipitation" under the action of high-temperature heat source of laser cladding, which can improve the wettability of the strengthening phase and steel, and effectively avoid the cracks in the hard surface coating. The high-temperature spheroidized steel binder ball has high sphericity, good fluidity and uniform distribution of strengthening phase, so that the uniformity of powder feeding in the laser cladding process can be improved, the deposition rate of the strengthening phase can be improved, and the wear resistance of the hard surface coating can be improved.

[0008] The application relates to a steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a shale mining cutter.

[0009] (1) high-temperature spheroidized steel-bonded hard alloy ball particle

[0010] The cleaned steel-bonded hard alloy powder is subjected to high-temperature spheroidization treatment. In the process, the powder particles absorb a large amount of heat in the high-temperature plasma, the surface is rapidly melted, and then the steel binder ball is formed by cooling in the inert gas under the action of surface tension. The powder has good uniformity of the strengthening phase, high sphericity and good fluidity. The high-temperature spheroidization process parameters are as follows: gap voltage is 45V-55V, discharge current is 500A, pulse width is 2000us, pulse interval is 200us, and electrode rotating speed is 3000r / min.

[0011] (2) hard surface coating

[0012] After the steel base surface is polished and rusted, the surface is cleaned in acetone and anhydrous ethanol, the surface grease is removed, and the surface is dried. The laser cladding process parameters are as follows: laser power is 1400W, scanning speed is 600mm / min, powder feeding rate is 1r / min, and overlapping distance is 48%.

[0013] The application relates to a steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a shale mining cutter.

[0014] As a preferred scheme, the application relates to a steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a shale mining cutter.

[0015] As a further preferred scheme, the application relates to a steel-bonded hard alloy ball particle reinforced hard surface coating applied to the protection of a shale mining cutter. The D10 of the spheroidized TM52 hard alloy particle is 50-51.5um, the D50 is 90-91um, and the D90 is 140-141um.

[0016] As a further preferred embodiment, the application provides a steel-bonded hard metal ball particle reinforced hard facing coating for protection of a shale mining tool, wherein the TM52 hard metal particles after spheroidization have a loose bulk density of 2.27 g / cm3 and a tapped density of 2.44 g / cm3.

[0017] The application provides a steel-bonded hard metal ball particle reinforced hard facing coating for protection of a shale mining tool, wherein the content of the reinforcing phase in the coating is 60-65 vol%. The reinforcing phase is TiC. Preferably, the TiC in the coating is composed of TiC particles with a particle size D1 of 50 nm-2 microns and TiC particles with a particle size D2 of 4 microns-20 microns. The inventors have found that such a distribution of TiC particles in the coating is conducive to enhancing the stability of the friction performance of the product, especially the stability of the friction coefficient after a period of friction (e.g. 10 min).

[0018] The application provides a steel-bonded hard metal ball particle reinforced hard facing coating for protection of a shale mining tool, wherein the hardness of the coating is 61.5-61.9 HRC.

[0019] The application provides a steel-bonded hard metal ball particle reinforced hard facing coating for protection of a shale mining tool, wherein the wear performance of the hard facing coating is tested by using HT-1000, and the selected parameters are as follows: a Si3N4 ball with a diameter of 2 mm is used as a friction pair (hardness is about 1700 HV), the selected load is 19.8 N, the total test time is 30 min, the rotation speed of the grinding ball is 560 r / min, and the friction path radius is 2 mm. The volume wear rate of the coating is (8.25-8.28) x 10 -7 mm 3 / N·m.

[0020] Principles and advantages of the application

[0021] Under the action of a high-energy heat source such as laser cladding, the reinforcing phase forms an interface reaction layer with a certain thickness between the steel through a "dissolution-reprecipitation" process, and has good wettability. At the same time, the particle size distribution of the reinforcing phase after the "dissolution-reprecipitation" process has a clear bimodal distribution, which is conducive to enhancing the stability of the friction performance of the product, especially the stability of the friction coefficient of the product after a period of friction.

[0022] The coating obtained by the application has a high reinforcing phase content (about 65 vol%), which is much higher than that of the existing Ni60 / WC coating without macroscopic defects (35 vol%). Therefore, the hardness (about 61.9 HRC) of the coating is relatively higher than that of the Ni60 / WC coating (54 HRC).

[0023] The application solves the problem of low hard phase content and insufficient wear resistance of WC / Ni60 hard face coating in industry due to mismatch of thermal expansion coefficient and uneven powder feeding. The obtained product has high strengthening phase deposition rate, high content and uniform distribution of strengthening phase in the hard face coating, and stable and excellent wear resistance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a morphology diagram of the hard face coating of the steel-bonded carbide pellets obtained in Example 1; Figure 1

[0025] Figure 2 is a morphology diagram of the hard face coating of the steel-bonded carbide pellets obtained in Example 1; Figure 2

[0026] Figure 3 is a morphology photograph of the Ni60 / WC hard face coating of the mudstone mining cutter currently used in industry; Figure 3

[0027] Figure 4 is a friction and wear coefficient curve diagram of the hard face coating obtained in Example 1; Figure 4

[0028] Figure 5 is a morphology diagram of the interface between the coating and the substrate in the product obtained in Example 1; Figure 5

[0029] Figure 6 is a morphology diagram of the product obtained in Comparative Example 1. Figure 6

[0030] Figure 7 is a microstructure diagram of the product obtained in Comparative Example 2; Figure 7

[0031] Figure 8 is a friction and wear coefficient curve diagram of the hard face coating obtained in Comparative Example 3; Figure 8

[0032] Figure 9 is a morphology diagram of the hard face coating obtained in Comparative Example 3. Figure 9 DETAILED DESCRIPTION Example 1

[0033] TM52 hard alloy steel powder was used as raw material, which was placed in a plasma spheroidizing device for high-temperature plasma spheroidizing to obtain spheroidized TM52 hard alloy particles. The D10 of the spheroidized TM52 hard alloy particles was 50.9 μm, the D50 was 90.4 μm, and the D90 was 140.3 μm. The loose bulk density was 2.27 g / cm3, and the tap density was 2.44 g / cm3.

[0034] The high-temperature spheroidizing process parameters were as follows: gap voltage was 45-55 V, discharge current was 500 A, pulse width was 2000 μs, pulse interval was 200 μs, and electrode rotation speed was 3000 r / min.

[0035]

[0036] ​​​​​​​​​After the steel base surface is polished and rusted, it is ultrasonically cleaned in acetone and anhydrous ethanol to remove surface grease and dried, and the spheroidized TM52 hard alloy particles prepared in the previous step are used as raw materials. Without adding any additives, the spheroidized TM52 hard alloy particles are cladded on the steel base surface by laser cladding process, and a hard-facing coating is obtained after cooling; the laser cladding process parameters are: laser power 1400W, scanning speed 600mm / min, powder feeding motor speed 1r / min, and overlap distance 48%.

[0037] In the obtained coating, the content of the strengthening phase is about 65vol% (the strengthening phase consists of TiC), and the hardness of the coating is 61.9HRC;

[0038] The wear-resistant coating detection method is: the wear resistance of the hard-facing coating is tested by HT-1000, and the selected parameters are: a 2mm diameter Si3N4 ball is used as the friction pair (hardness about 1700HV), the selected load is 19.8N, the total test time is 30min, the grinding ball rotation speed is 560r / min, and the friction path radius is 2mm. The wear-resistant coating detection result: the volume wear rate is 8.27x10 -7 mm 3 / N·m.

[0039] Comparative Example 1

[0040] Other conditions are the same as in Example 1, except that the laser power is 1200W and the scanning speed is 400mm / min. The obtained product has an uneven surface cladding layer, and there are obvious unmelted particles (as shown in Figure 6 ).

[0041] Comparative Example 2

[0042] Reference: Zhou D, Guo J, Xiong D, et al. Effect of TiC content on the properties of laser cladding Fe-based coating [J]. Applied Laser, 2021, 41(6): 7.

[0043] Using the technology of the reference, coarse particle TiC and Fe-based powder are used as raw materials, and the coating prepared by laser cladding technology has a TiC volume fraction of 30%, which has obvious cracks. The volume fraction of the strengthening phase in the hard-facing coating is only 40t%, and there is no obvious reaction interface between TiC and the binder phase, and the wettability of TiC and the binder phase is poor, and its morphology is as shown in Figure 7 .

[0044] Comparative Example 3: Hard-facing coating strengthened by spray-dried steel-bonded hard alloy powder

[0045] The steel powder with purity of 99.9% or above and TiC were accurately weighed according to the formula (the specific ratio is the same as and completely equal to that in Example 1), then a proper amount of alcohol was added into the mixed powder, and then the powder was put into a ball mill for wet grinding for 8-12 hours, then a certain amount of binder and dispersant were added to prepare a slurry, and then the slurry was put into the ball mill for wet mixing for a period of time, so that a uniform and stable slurry was obtained; then a powder with a particle size of 100-300 mesh was prepared through a spray drying tower. The process parameters of the spray drying are as follows: the temperature of the inlet / outlet of the spray tower is 165℃ / 100℃, the motor speed of the spray disc is 20Hz (the rotating speed is 6000rpm), and the rotating speed of the feeding pump is 50rpm. Finally, the slurry was degreased and sintered at 800-1000℃ to obtain an agglomerated powder. The D10 of the spray-dried TM52 cemented carbide particles is 49.7μm; the D50 is 100.4μm, and the D90 is 150.3μm. The loose bulk density is 1.86g / cm 3 , and the tap density is 1.97g / cm 3 .

[0046] After the steel base surface was polished and rusted, it was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface grease and dried. The spray-dried TM52 cemented carbide powder prepared in the previous step was used as the raw material, and the spray-dried TM52 cemented carbide powder was cladded on the steel base surface by laser cladding without adding any additives. After cooling, a hard-facing coating was obtained. The process parameters of the laser cladding are as follows: the laser power is 1400W, the scanning speed is 600mm / min, the rotating speed of the powder feeding motor is 1r / min, and the overlapping distance is 48%.

[0047] In the obtained coating, the content of the strengthening phase is 52vol% (the strengthening phase consists of TiC), and the hardness of the coating is 55HRC.

[0048] The wear-resistant coating detection method is as follows: the HT-1000 was selected to test the wear resistance of the hard-facing coating, the selected parameters are as follows: a Si3N4 ball with a diameter of 2mm was selected as the friction pair (the hardness is about 1700HV), the selected load is 19.8N, the total test time is 30min, the rotating speed of the grinding ball is 560r / min, and the friction path radius is 2mm.

[0049] The friction and wear coefficient of the coating is unstable, and the characterization diagram is shown in Figure 8 . The morphology of the coating is shown in Figure 9 .

Claims

1. A steel-bonded hard metal pelletized hardfacing coating for use in the protection of shale mining tools, characterized in that; Prepared by the following steps: (1) High temperature spheroidized steel bonded carbide pellets The cleaned steel-bonded cemented carbide powder is subjected to high-temperature spheroidization treatment, and the high-temperature spheroidization process parameters are: gap voltage of 45V-55V, discharge current of 500A, pulse width of 2000μs, pulse interval of 200μs, and electrode speed of 3000r / min; the steel-bonded cemented carbide is selected from TM52 steel-bonded cemented carbide; The D10 of TM52 cemented carbide particles after spheroidization is 50-51.5μm, D50 is 90-91μm, and D90 is 140-141μm; The bulk density of the spheroidized TM52 cemented carbide particles was 2.27 g / cm 3 , and the tap density was 2.44 g / cm 3 ; (2) Hard surface coating After the steel base surface was polished and derusted, it was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface grease and dried. The laser cladding process parameters were: laser power 1400W, scanning rate 600mm / min, powder feeding rate 1r / min, and overlap spacing 48%.

2. A steel-bonded hard metal bead reinforced hardfacing coating for use in the protection of a shale excavating tool according to claim 1, characterized in that: In the coating, the content of the reinforcement phase is 60-65 vol%.

3. A steel-bonded hard-metal bead reinforced hard-facing coating for use in the protection of a shale-mining cutter, according to claim 2, characterized in that: The strengthening phase is TiC.

4. A steel-bonded carbide ball particle reinforced hardfacing coating applied to the protection of a shale excavating cutter according to claim 2, characterized in that: The TiC in the coating consists of TiC particles with a particle size of D1 and TiC particles with a particle size of D2. The value of D1 is 50nm-2 microns; the value of D2 is 4 microns-20 microns.

5. A steel-bonded hard metal bead reinforced hardfacing coating for use in the protection of a shale excavating tool according to claim 3, characterized in that: The hardness of the coating is 61.5-61.9HRC.

6. A steel-bonded carbide ball particle reinforced hardfacing coating applied to the protection of a shale excavating cutter according to claim 3, characterized in that: The wear performance of the hard-facing coating is tested by using HT-1000, and the selected parameters are as follows: the Si3N4 ball with a diameter of 2 mm is used as a friction pair, the selected load is 19.8 N, the total test time is 30 min, the rotation speed of the grinding ball is 560 r / min, the friction path radius is 2 mm, and the volume wear rate of the coating is (8.25~8.28)×10 -7 mm 3 / N·m.

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