CN101245461A - Method of producing (FeAl+Cr7C3)/(gamma Fe, Ni) composite coating - Google Patents

Abstract

The invention provides a preparation method of (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating. Low-carbon steel is placed on the plasma cladding workbench as the base material, and the distance from the plasma moment 27-30mm; on the basis of the iron-based alloy powder system, add Al ₂ O ₃ powder with a weight percentage of 10-15%, and ball mill the powder for 30-60 minutes to make the powder fully mixed to prepare the coating material; The material is loaded into the powder feeder of the plasma cladding equipment for the preparation of the plasma cladding coating. Set the plasma cladding process parameters as follows: working current 250-300A, scanning speed 350-400mm/min, powder feeding gas (Ar): 0.4-0.8m ³ /h, plasma gas (Ar): 0.4-0.8m ³ / h, protective gas (Ar): 0.4-0.8m ³ /h. The coating prepared by the invention has fine crystal grains, uniform composition, high coating hardness, and excellent wear resistance and high temperature oxidation resistance.

Description

A preparation method of (FeAl+Cr7C3)/γ-(Fe, Ni) composite coating

technical field

The invention belongs to the technical field of surface coatings, and relates to an intermetallic compound composite coating and a preparation method thereof.

Background technique

FeAl intermetallic compounds have many excellent properties, including high melting point, low density, good thermal conductivity, and excellent oxidation resistance, and are potential high-temperature structural materials. However, there are still the following problems in its wide industrial application. One is room temperature brittleness and low yield strength, which limit the processability of FeAl intermetallic compounds at room temperature. Many researchers have carried out research work in this area. According to the report of the Journal of Materials Heat Treatment (2007, Vol.28, No.4, P16-21), the room temperature mechanical properties of FeAl intermetallic compounds were improved by hot pressing and sintering. ; Journal of Tsinghua University (Natural Science Edition) (2004, Vol.44, No.5, P 585-588) reported that pure Al powder was pre-coated on the surface of 45 steel, and a layered alloy with layered characteristics was synthesized by beam alloying. The Fe/Al compound coating has the characteristics of organizational gradient transition, thus improving its comprehensive mechanical properties. Liu Anqiang of Kunming University of Technology (Thermal Processing Technology, 2006, Vol.35, No.20, P26-42) prepared FeAl alloy by mechanical alloying and vacuum sintering, and obtained good mechanical properties at room temperature. There are still many researches on this aspect, but the fruitful ones are relatively few, and the common point of the methods used is that the preparation conditions are relatively harsh, the equipment is complicated, the energy consumption is high, and the production cycle is long. These higher costs cannot meet the industrialization needs of FeAl materials. In addition, most of the current research is on the preparation of FeAl monolithic materials, and there are few studies on the preparation of FeAl intermetallic compound coatings, and this monolithic material often cannot meet the requirements of use, because under many working conditions, it is necessary to The combination of high surface hardness and internal toughness of the material. This has accelerated the development of coating technology to a certain extent. At present, the coating technologies for preparing FeAl intermetallic compounds mainly include thermal spraying and laser cladding. Thermal spraying coatings have poor adhesion and large coating porosity; however, large lasers for laser cladding are expensive and are not conducive to industrial applications.

Plasma cladding technology is a surface coating technology developed in recent years. The high-energy plasma beam has high energy and good stability. It can be operated in the atmosphere. The compatibility, melting point, density and other properties of the composition are limited, and the alloy layer that cannot be obtained by the usual metallurgical method is obtained by using any powder ratio, that is, the material is A→B before and after the metallurgical reaction, or A+B→C, Or A+B→C+D, etc. (of course also including A→A, or A+B→A+B), which provides sufficient conditions for the in-situ generation of intermetallic compounds, and under the action of high-energy beams, the powder and The surface layer of the substrate is melted at the same time, and the metallurgical layer and the substrate reach a metallurgical bonding state. Plasma cladding equipment does not need a vacuum system, and the cost is only 1/5 to 1/10 of that of laser cladding equipment with the same power. It has high production efficiency and is easy to operate and maintain. However, the preparation and development of plasma cladding coatings are still far from enough. The preparation of plasma cladding technology is limited to conventional coatings such as Fe-based and Ni-based coatings, and it is difficult to expand its application fields.

Contents of the invention

The object of the present invention is to provide a kind of preparation method of (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating, FeAl intermetallic compound and Cr ₇ C ₃ hard phases are introduced in the coating, and Composite with ductile phase γ-(Fe, Ni), effectively improve the mechanical properties of intermetallic compound composite materials, and broaden the application field of intermetallic compound. The plasma cladding technology adopted can overcome the disadvantages of the original intermetallic compound coating technology, such as large thermal stress of the coating, poor bonding force with the substrate, and high cost.

The preparation process of the (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating of the present invention is as follows: the base material is placed on the plasma cladding workbench, and the distance from the plasma moment is 27-30 mm; On the basis of the base alloy powder system, add Al ₂ O ₃ powder with a weight percentage of 10-15%, and ball mill the powder for 30-60 minutes, so that the powder is fully mixed to prepare a coating material; put the coating material into the plasma cladding equipment In the powder feeder, the plasma cladding process parameters are set as follows: working current 250-300A, scanning speed 350-400mm/min, powder feeding gas (Ar): 0.4-0.8m ³ /h, plasma gas (Ar): 0.4～0.8m ³ /h, protective gas (Ar): 0.4～0.8m ³ /h. Start the switch to prepare the plasma cladding coating. After the coating is cooled, the grinding wheel grinds away impurities such as surface scale to obtain a non-porous, crack-free, bright and dense (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating.

The base material is low carbon steel with a thickness of 5-10 mm.

The alloying element weight percent of the iron-based alloy powder is: Cr 30.0-35.0%, Ni 4.5-5.5%, Mo 3.0-4.5%, B 2.0-3.5%, Si 3.5-5.0%, Fe balance.

The particle size of the powder ranges from 106 to 180 microns.

The present invention starts from the coating material. When preparing the FeAl intermetallic compound, a certain amount of Al ₂ O ₃ powder is added to the iron-based alloy powder system and uniformly mixed as the coating material. During the plasma cladding process, Al ₂ O ₃ reacts with alloying elements to form FeAl intermetallic compound, hard phase Cr ₇ C ₃ and good ductility γ-(Fe, Ni) in situ, as shown in Figure 1 According to the results, a rapid solidification structure with fine grains and uniform composition can be obtained; the coating has high hardness, excellent wear resistance and high temperature oxidation resistance.

The microstructure analysis of the coating found that the coating microstructure is a rapid solidification structure with fine grains, uniform composition, dispersed distribution of FeAl and Cr ₇ C ₃ , in which FeAl intermetallic compound and carbide Cr ₇ C ₃ grow side by side. The microhardness of the coating is about HV _0.2 900-1100. Wear tests at room temperature and 500°C were carried out on the SRV high-temperature friction and wear testing machine. The friction coefficients at room temperature and high temperature are about 0.35 and 0.3 respectively. High temperature has excellent wear resistance. Carry out high-temperature cycle oxidation at 700°C in a high-temperature resistance furnace, take it out and weigh it every 10 hours, the test shows that in the first 10 hours, the oxidation weight gain is relatively fast, and the weight gain rate is 0.0152～0.0203mg·cm ^-2 ·h ^{- 1.} A dense oxide film is formed on the surface of the coating, which hinders the further oxidation of the coating, and then the oxidation weight gain is relatively slow, and the weight gain rate is 0.0040-0.0086 mg·cm ^-2 ·h ^-1 . Excellent resistance to high temperature oxidation.

Description of drawings

Figure 1 (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating XRD pattern;

Figure 2 Example 1 (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating morphology;

Figure 3 Example 2 (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating morphology;

Fig. 4 Microstructure of (FeAl+Cr ₇ C ₃ )/γ-(Fe, Ni) composite coating in Example 3.

Detailed ways

Example 1. Weigh 200g of the coating material, wherein the content of each component is 60g of Cr, 10g of Ni, 8g of Mo, 6g of B, 8g of Si, 88g of Fe and 20g of Al ₂ O ₃ . The alloy powder is put into a low-temperature ball mill and ball-milled for 30 minutes. The particle size range of the powder is 106-180 microns, and it is fully mixed to prepare a coating material. Put the coating material into the powder feeder of the plasma cladding equipment, set the plasma cladding process parameters as follows: working current 280A, scanning speed 380mm/min, powder feeding gas (Ar): 0.6m ³ /h, plasma gas (Ar): 0.6m ³ /h, shielding gas (Ar): 0.6m ³ /h; cut the low-carbon steel plate into a 150mm×100mm test block with a thickness of 6mm as the substrate, and place it 30mm directly below the plasma torch on the workbench; when ready, start the plasma cladding equipment to prepare a composite coating. After the cladding is completed, after the coating is cooled, use a grinding wheel to grind off the scale and slag on the surface of the coating to obtain a smooth, bright and defect-free coating. The grains in the coating are fine, the composition is uniform, and it is a rapidly solidified structure with dispersed distribution of FeAl and Cr ₇ C ₃ , as shown in Figure 2; the composition (percentage by weight) of the composite coating is analyzed by energy spectrum: Cr 31.5%-Fe 44.2 %-Ni 5.2%-Mo 3.4%-Si 3.5%-Al 12.2%.

The microhardness of the coating is about HV _0.2 1000, and its coefficient of friction at room temperature and high temperature is about 0.35 and 0.3, respectively, and has excellent wear resistance. The high-temperature cyclic oxidation test at 700°C shows that in the first 10 hours of oxidation, the oxidation weight gain rate is 0.018 mg·cm ^-2 ·h ^-1 , and a dense oxide film is formed on the surface of the coating. The rate is 0.005 mg·cm ^-2 ·h ^-1 . Excellent resistance to high temperature oxidation.

Example 2. Weigh 200g of the coating material, wherein the content of each component is 65g of Cr, 10g of Ni, 8g of Mo, 6g of B, 8g of Si, 73g of Fe and 30g of Al ₂ O ₃ . Put the alloy powder into a low-temperature ball mill and mill it for 40 minutes to make it fully mixed and prepare the coating material. Put the uniformly mixed coating material into the powder feeder of the plasma cladding equipment, set the plasma cladding process parameters as follows: working current 300A, scanning speed 400mm/min, powder feeding gas (Ar): 0.5m ³ /h , plasma gas (Ar): 0.5m ³ /h, shielding gas (Ar): 0.5m ³ /h; cut the Q235 steel plate into 150mm×100mm, 8mm thick test piece, as the substrate, put it in the plasma torch On the workbench 30mm below; when ready, start the plasma cladding equipment to prepare composite coating. After the cladding is completed, after the coating is cooled, use a grinding wheel to grind off the scale and slag on the surface of the coating to obtain a bright coating. The coating structure is a rapid solidification structure with fine grains, uniform composition, and dispersed distribution of FeAl and Cr ₇ C ₃ , as shown in Figure 3; the composition (weight percentage) of the composite coating is: Cr 32.5%-Fe 41.2 The microhardness of %-Ni 4.5%-Mo3.2%-Si 3.4%-Al 15.2% coating can reach HV _0.2 1100, and its coefficient of friction at room temperature and high temperature is about 0.35 and 0.3 respectively, with excellent wear resistance performance. The high-temperature cycle oxidation test at 700°C shows that in the first 10 hours of oxidation, the oxidation weight gain rate is 0.015 mg·cm ^-2 ·h ^-1 , and a dense oxide film is formed on the surface of the coating. It is 0.004 mg·cm ^-2 ·h ^-1 . Excellent resistance to high temperature oxidation.

Example 3. Weigh 200g of the coating material, wherein the content of each component is 65g of Cr, 10g of Ni, 8g of Mo, 6g of B, 8g of Si, 79g of Fe and 24g of Al ₂ O ₃ . Put the alloy powder into a low-temperature ball mill and mill it for 60 minutes to make it fully mixed. Put the coating material into the powder feeder of the plasma cladding equipment, set the plasma cladding process parameters as follows: working current 300A, scanning speed 400mm/min, powder feeding gas (Ar): 0.6m ³ /h, plasma gas (Ar): 0.6m ³ /h, shielding gas (Ar): 0.6m ³ /h; cut the Q235 steel plate into a test piece with a size of 150mm×100mm and a thickness of 9mm, as the matrix material of the intermetallic compound composite coating, Put it on the workbench 30mm directly below the plasma torch; when ready, start the plasma cladding equipment to prepare a composite coating. After the cladding is completed, after the coating is cooled, use a grinding wheel to grind off the scale and slag on the surface of the coating to obtain a bright coating. The coating structure is a rapid solidification structure with fine grains, uniform composition, and dispersed distribution of FeAl and Cr ₇ C ₃ , as shown in Figure 4; the composition (weight percentage) of the composite coating is: Cr 31.5%-Fe 43.2 %-Ni 4.8%-Mo 3.4%-Si 3.5%-Al 13.5%. The microhardness of the coating is about HV _0.2 980, and its coefficient of friction at room temperature and high temperature is about 0.35 and 0.3, respectively, and has excellent wear resistance. The high-temperature cycle oxidation test at 700°C shows that in the first 10 hours of oxidation, the oxidation weight gain rate is 0.020 mg·cm ^-2 ·h ^-1 , and a dense oxide film is formed on the surface of the coating. It is 0.007 mg·cm ^-2 ·h ^-1 . Excellent resistance to high temperature oxidation.

Claims (5)

1, a kind of (FeAl+Cr ₇C ₃)/γ-(Fe, the Ni) preparation method of compound coating is characterized in that: body material is positioned on the plasma cladding worktable, with the distance of plasma square be 27～30mm; On the basis of iron(-)base powder system, the interpolation weight percent is 10～15% Al ₂O ₃Powder with powder ball milling 30～60min, makes the powder thorough mixing be mixed with coated material; Coated material is packed in the powder feeder of plasma melting coating equipment into plasma cladding working current 250～300A, sweep velocity 350～400mm/min, powder feeding gas 0.4～0.8m ³/ h, plasma (orifice) gas 0.4～0.8m ³/ h, protection gas 0.4～0.8m ³/ h.

2, preparation method as claimed in claim 1 is characterized in that, described body material is a soft steel, and thickness is 5～10mm.

3, preparation method as claimed in claim 1, it is characterized in that the alloying element weight percent of described iron(-)base powder is: Cr 30.0～35.0%, Ni 4.5～5.5%, Mo 3.0～4.5%, B 2.0～3.5%, Si 3.5～5.0%, Fe surplus.

4, preparation method as claimed in claim 1 is characterized in that, described powder size scope is 106～180 microns.

5, preparation method as claimed in claim 1 is characterized in that, powder feeding gas, plasma (orifice) gas, protection gas all use argon gas.

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