CN102773473B - Iron nickel chrome molybdenum base powder for laser cladding and method for preparing same - Google Patents

Abstract

An iron-nickel-chromium-molybdenum-based powder material for laser cladding and a preparation method thereof belong to the technical field of surface engineering. The weight percentage of each component of the powder is: titanium powder: 10-18wt.%; graphite carbon powder: 2-4.5wt.%; niobium carbide powder: 6-15%; iron-nickel-chromium-molybdenum alloy powder: The balance; wherein, the composition of the iron-nickel-chromium-molybdenum alloy powder is: nickel: 20-26wt.%, chromium: 23-26wt.%, molybdenum: 6-15wt.%, iron: balance. The advantages are: using a high-energy-density laser beam to melt the mixed powder, forming a wear-resistant and corrosion-resistant cladding layer on the surface of the steel substrate with iron-nickel-chromium-molybdenum alloy as the continuous phase and carbide ceramics as the reinforcing phase. It achieves metallurgical combination with the matrix and low dilution rate. The method of the invention has the advantages of low preparation cost, long wear-resistant and corrosion-resistant life of the cladding layer, simple process, etc., and can significantly prolong the wear-resistant and corrosion-resistant life of components such as agitators, slurry circulation pumps and seawater circulation pumps.

Description

Iron-nickel-chromium-molybdenum-based powder material for laser cladding and preparation method thereof

technical field

The invention belongs to the technical field of surface engineering, and in particular provides an iron-nickel-chromium-molybdenum-based powder material for laser cladding and a preparation method thereof.

Background technique

The agitator and the slurry circulation pump are one of the key equipment in the desulfurization system of the thermal power plant, and their wear and corrosion problems are important reasons that affect the safe and economical operation of the desulfurization system.

The agitator consists of a stirring mechanism, a shaft and a drive system equipped with a drive motor. The agitator generally uses three-blade propeller blades, and the blade material is stainless steel. The function of installing the agitator is: (1) prevent solid particles from settling in the slurry tank, and ensure that the slurry can be evenly transported to the next process; (2) strengthen the diffusion of oxidizing air, and promote the oxidation of calcium sulfite and gypsum Crystal growth and dissolution of limestone.

The slurry in the absorption tower is acidic, and the slurry contains solid particles such as CaCO ₃ and a large amount of highly corrosive chloride ions, the concentration of which can reach 1-2%. Therefore, the reasons for the failure of the hub and blade of the agitator are wear and corrosion. As the wear and corrosion of the agitator blades increase, it will cause uneven stirring of the slurry, resulting in local deposition of solid particles at the bottom of the tank and deposition at the pump inlet; this problem will cause increased wear of the slurry circulating pump. The agitator hub is generally made of 1.4529 alloy with good corrosion resistance or other corrosion-resistant alloys. Due to the high speed of the agitator impeller, the blade material is required to have higher wear and corrosion resistance than the hub material.

The slurry circulating pump is a large flow centrifugal pump, which is used to circulate the slurry in the absorption tower. The slurry in the absorption tower is a solid-liquid two-phase flow medium, and the solid components in the slurry are limestone and gypsum, and the weight concentration is generally about 20%. Depending on the installed capacity of the unit and the sulfur content of the coal fired, the slurry circulation flow rate of the desulfurization absorption tower is usually between 4000 and 12000m ³ /h, and the lift is between 16 and 30m. In the flue gas desulfurization capacity, the power consumption of the slurry circulating pump accounts for more than one-third of the power consumption of the entire desulfurization island. Therefore, large flow and high efficiency are the technical requirements for the pump. Flue gas will form sulfuric acid, hydrochloric acid and other acidic mixtures during the cycle absorption process, and gradually enrich with the prolongation of the cycle time, the chloride ion concentration of the slurry is in the range of 20000-60000 mg/L, and the pH value is generally between 4.5-6 . Slurry circulating pumps work in the above-mentioned complex media containing solids and corrosive high-speed flows, and the problems of corrosion and wear of the materials of the flow-passing parts are particularly prominent. Wear and corrosion will cause problems such as continuous reduction of pump efficiency and vibration. Therefore, the corrosion and wear resistance of the material of the slurry circulation pump's flow parts is an important indicator that determines the service life and energy consumption of the pump. The circumferential velocity at any point of the blade of the slurry circulation pump is proportional to the rotational speed and diameter, so the velocity reaches the maximum at the outer diameter of the impeller, which intensifies the wear of the particles in the slurry and the blade, resulting in the most serious wear at the corresponding position. There are two kinds of anti-corrosion and wear-resistant technologies for the flow parts of the slurry circulation pump in the world. One is to use the cast iron shell and rubber lining technology, that is, the rubber-lined pump; the other is to use the anti-corrosion and wear-resistant alloy to make the pump. Flow parts, namely alloy pumps. The manufacturing cost of the alloy pump is higher, but the operation reliability and life of the pump device are better than that of the rubber-lined pump.

The components of the slurry circulation pump are usually made of high-chromium corrosion-resistant and wear-resistant alloys and duplex stainless steel, which are F30%CrMo (enterprise brand Cr30) and Z3CNUD2605M (enterprise brand 2605). In view of the high content of chloride ions in the flue gas desulfurization slurry, domestic and foreign manufacturers added appropriate amounts of Ni and Cu elements to the original composition of Cr30 to improve its resistance to chloride ion corrosion. The company code of the improved material is Cr30A, Cr30A is used to manufacture the impeller of the rotating part in the slurry pump and the front and rear guard plates matched with it. Its microstructure is austenite + carbide + a small amount of ferrite, and the microhardness is in the range of 450-560HV. Although the above materials have good wear and corrosion resistance, their wear and corrosion resistance still cannot meet the requirements of long-life and efficient operation of thermal power plants. The maintenance cycle of the impeller of the slurry circulation pump is generally 4000-8000 hours. For cast parts of Cr30 and Cr30A materials, due to their high chromium content (chromium content 35-40wt.%) and poor fracture toughness, such as arc welding, argon arc, and plasma cladding methods are used to prepare cladding layers on the surface of such materials , Due to the large heat-affected zone and high thermal stress in the heat-affected zone, it is very easy to cause penetrating macroscopic cracks on the surface of Cr30 and CR30A materials and make the components scrapped. Therefore, for the slurry circulating pump impeller and other flow-passing parts with less serious wear and corrosion, cold repair is often used to prolong their life. For example, Metaline ceramic-glue composite materials can be used to repair pits, or spray such materials The impeller and the inner wall of the pump form a wear-resistant and corrosion-resistant layer. Due to the low bonding strength (generally less than 20MPa) of this type of wear-resistant coating, its service life generally does not exceed 4500 hours.

Contents of the invention

The object of the present invention is to provide a kind of iron-nickel-chromium-molybdenum-based powder material and preparation method thereof for laser cladding; Utilize laser beam cladding powder material described in the present invention, can be used in thermal power plant agitator blade, pump and The wear-resistant and corrosion-resistant cladding layer is formed in the severely worn part of the impeller flow parts, which is suitable for the wear-resistant and corrosion-resistant surface treatment of the agitator for the desulfurization system of the thermal power plant, the slurry circulation pump and the flow parts of the seawater circulation pump used in various power plants.

The surface microhardness of the cladding layer formed by cladding the powder material described in the present invention by laser beam is in the range of 500-1000HV. The advantage of the laser cladding method is that the heat-affected zone on the surface of the workpiece is extremely small, which can effectively avoid the deformation or cracking of the base material due to the thermal stress generated during the cladding process. The invention breaks through the limitations of low bonding strength and short service life of the existing wear-resistant and corrosion-resistant coating or rubber-lined layer, and enables the wear-resistant and corrosion-resistant cladding layer to achieve metallurgical bonding with the substrate.

The present invention is realized through the following steps.

The weight percentage of each component of powder material of the present invention is:

Titanium powder (particle size -140+325 mesh, purity ≥99.5%, where "-140+325 mesh" means the powder particle size ranges from 325 mesh to 140 mesh): 10-18%; graphite carbon powder (purity ≥99%) : 2-4.5%; niobium carbide (NbC) powder (particle size -140+325 mesh, purity ≥99.5%): 6-15%; iron-nickel-chromium-molybdenum alloy powder (particle size-140+325 mesh): more than Amount; Wherein, the composition of iron-nickel-chromium-molybdenum alloy powder is: nickel: 20-26%, chromium: 23-26%, molybdenum: 6-15%, iron: balance.

The preparation method of the iron-nickel-chromium-molybdenum alloy powder is an existing mature process, that is, the principle of its production is: melting the alloy in a furnace, passing through a tundish, and injecting the melt into the gas atomization zone for atomization The iron-nickel-chromium-molybdenum alloy powder is obtained, and the powder is sieved to obtain the iron-nickel-chromium-molybdenum alloy powder with the required particle size.

The preparation technology of powder material of the present invention is as follows:

(1) Weigh various powder raw materials according to the weight percentage of each component of the powder;

(2) Put the weighed various powder raw materials into a drying oven for drying, the temperature of the drying oven is 100-150°C, and the drying time is 2-3 hours;

(3) Use dry powder mixing equipment (such as V-type mixer) to mix powder raw materials to form mixed powder materials, and the mixing time is 3-5 hours;

(4) Put the mixed powder material into a plastic bucket for sealed storage.

After cladding the above-mentioned powder materials by laser, a ceramic-metal composite material cladding layer is formed. Among them, iron-nickel-chromium-molybdenum alloy is the continuous phase with high corrosion resistance in the cladding layer, and NbC and TiC _x (x in the range of 0.5-1) synthesized by reaction in the cladding process are the reinforcing phases in the cladding layer ; The ceramic-metal composite cladding layer has high wear resistance and corrosion resistance.

3. Preparation process of cladding layer

The invention can be used to prepare wear-resistant and corrosion-resistant cladding layers on new agitator blades, slurry circulating pumps and seawater circulating water pump flow parts, and can also be used to repair worn and corroded parts. Since the entire blade is protected by a cladding layer, the material of the blade and hub can be replaced by stainless steel with good toughness (such as 316 stainless steel) for materials with poor toughness such as Cr30 and CR30A. The steps to make are:

(1) According to the design size, the blades and hubs are made of stainless steel

According to the design size, stainless steel blades, hubs and other components required by the agitator or the slurry circulation pump are made by forging or casting.

(2) Prepare wear-resistant and corrosion-resistant cladding layers on the surface of the blade and hub respectively

Laser cladding process is an existing mature technology, such as Nd:YAG lamp-pumped solid-state laser with a wavelength of 1064nm, fiber coupling, and power of 700-1500W; if a semiconductor direct output laser is selected, its output power is 2-4kW . During laser cladding, the laser head is controlled by the numerical control mechanical arm, and lap cladding is carried out on the wear-resistant and corrosion-resistant areas of the blades and hubs (the area where the blades are welded on the hubs is not clad), and the single-layer cladding layer The thickness is 200-1000 μm. The thickness of the cladding layer can reach 600-3000 μm by adopting the multi-layer cladding method.

(3) Weld the blade with cladding layer to the hub and other components

Weld cladding blades to hubs and other components to form complete impellers for agitators or slurry circulation pumps.

The advantages of the present invention are: using a high-energy-density laser beam to melt the mixed powder, and form a wear-resistant and corrosion-resistant material with iron-nickel-chromium-molybdenum alloy as the continuous phase (matrix phase) and carbide ceramics as the reinforcing phase on the surface of the steel matrix. The cladding layer, the cladding layer and the substrate achieve metallurgical bonding, and the dilution rate is low. The method of the invention has the advantages of low preparation cost, wear-resistant cladding layer, long corrosion-resistant life, simple process, etc., and can significantly prolong the wear-resistant and corrosion-resistant life of components such as agitators, slurry circulation pumps and seawater circulation pumps.

Description of drawings

Figure 1 is a schematic diagram of the mixer.

FIG. 2 is a schematic diagram of a slurry circulating pump, with a blade 1 and a hub 2 .

Figure 3 is a scanning electron microscope photo of the cladding layer section, in which the small polygonal or round white particles are ceramic phases.

Fig. 4 is the variation curve of the microhardness of the cladding layer section with thickness.

Detailed ways

Example 1: Preparation of a wear-resistant and corrosion-resistant cladding layer on the surface of the agitator blade

1. Preparation of powder materials

1. Preparation of powder raw materials: the weight percentage range of the powder raw materials is as follows:

Titanium powder (particle size-140+325 mesh, purity 99.5%): 12wt.%; graphite carbon powder (purity 99%): 3 wt.%; niobium carbide powder (particle size-140+325 mesh, purity 99.5%): 8 wt.%; iron-nickel-chromium-molybdenum alloy powder (grain size-140+325 mesh): balance; wherein, the composition of iron-nickel-chromium-molybdenum alloy powder is: nickel: 20wt.%, chromium: 23wt. %, molybdenum: 8wt.%, iron: balance.

Iron-nickel-chromium-molybdenum alloy powder is prepared by the existing mature gas atomization method.

2. Mixing process of powder raw materials

(1) According to the various powder ratios described in step 1, weigh the various powders required for the powder raw materials;

(2) Put the powder raw material into a drying oven for drying, the temperature of the drying oven is 120°C, and the drying time is 3 hours;

(3) Use a ball mill to mix the powder raw materials to form a mixed powder material, and the mixing time is 3 hours;

(4) Seal and store the mixed powder materials in plastic bags.

2. Preparation process of cladding layer

A wear-resistant and corrosion-resistant cladding layer was prepared on the surface of a 300MW agitator blade in the desulfurization system of a thermal power plant, and the number of blades was 3.

The process steps of making the cladding layer on the surface of the blade are:

(1) Stainless steel is used to make blades and hub materials

The material of the blade and the hub is 316L stainless steel, which has good corrosion resistance.

(2) Preparation of wear-resistant and corrosion-resistant cladding layer on the blade surface

The equipment for preparing the cladding layer is mainly composed of a Nd:YAG lamp-pumped solid-state laser with an output power of 700W, a screw-type synchronous powder feeder, a numerically controlled manipulator, and a cladding workbench. Fix the blade on the cladding workbench by spot welding before cladding. During cladding, the powder material is placed in the storage tank of the screw-type powder feeder, and the laser head is controlled by the numerical control mechanical arm to perform lap cladding on the area where the blade requires wear and corrosion protection. During cladding, the output power of the laser is 600kW, the relative horizontal moving speed of the laser head and the workpiece is 4mm/s, and the vertical distance between the exit of the laser head and the surface of the workpiece is controlled by the numerical control mechanical arm (30mm), and the obtained single-layer cladding layer The average thickness is 300 μm. Using the two-layer cladding method, the average thickness of the cladding layer reaches 600 μm, and the minimum microhardness of the obtained cladding layer surface is 550 HV.

(3) Weld the blade with cladding layer to the hub

Weld the blade with the cladding layer to the hub to form a complete agitator (see Figure 1 for its shape).

Example 2: Preparation of wear-resistant and corrosion-resistant cladding layer on the surface of the impeller of the slurry circulation pump

1. Preparation of powder materials

1. Preparation of powder raw materials: the weight percentage range of the powder raw materials is as follows:

Titanium powder (particle size-140+325 mesh, purity 99.5%): 15 wt.%; graphite carbon powder (purity 99%): 3.7wt.%; niobium carbide (NbC) powder (particle size-140+325 mesh, purity 99.5 %): 10 wt.%; iron-nickel-chromium-molybdenum alloy powder (grain size-140+325 mesh): balance; wherein, the composition of iron-nickel-chromium-molybdenum alloy powder is: nickel: 26wt.%, Chromium: 25wt.%, molybdenum: 10wt.%, iron: balance.

2. Mixing process of powder raw materials

(1) According to the various powder ratios described in step 1, weigh the various powders required for the powder raw materials;

(2) Put the powder raw material into a drying oven for drying, the temperature of the drying oven is 120°C, and the drying time is 3 hours;

(3) Use a ball mill to mix the powder raw materials to form a mixed powder material, and the mixing time is 3 hours;

(4) Seal and store the mixed powder materials in plastic bags.

2. Preparation process of cladding layer

The wear-resistant and corrosion-resistant cladding layer was prepared with a 300MW mixed-flow slurry circulation pump impeller in the desulfurization system of a thermal power plant. The impeller type is semi-open and the number of blades is 5.

The manufacturing process steps of the impeller are:

(1) The blades and hubs are made of stainless steel according to the design size

According to the design size, 316L stainless steel is selected as the blade and hub material, the blade is made by forging, and the hub is made by casting.

(2) Prepare wear-resistant and corrosion-resistant cladding layers on the surface of the blade and hub respectively

The equipment for preparing the cladding layer is mainly composed of a semiconductor direct output laser with an output power of 3kW, a screw-type synchronous powder feeder, a numerically controlled manipulator, and a cladding workbench. During cladding, the powder material is placed in the storage tank of the screw type powder feeder, and the laser head is controlled by the numerical control mechanical arm, and the wear-resistant and corrosion-resistant protection areas of the blade and the hub are respectively placed on the hub The area where the blade is welded is not clad) for lap cladding. The output power of the laser during cladding is 2.5kW, the relative horizontal moving speed of the laser head and the workpiece is 10mm/s, and the vertical distance between the exit of the laser head and the surface of the workpiece is controlled by the numerical control mechanical arm (30mm), and the obtained single-layer cladding layer The average thickness is 800μm. Using the 2-layer cladding method, the average thickness of the cladding layer reaches 1600 μm, and the minimum surface hardness of the obtained cladding layer is 650HV.

(3) Weld the blade with cladding layer to the hub

The blades with cladding layer are welded to the hub to form a complete impeller.

Claims (2)

1. iron Ni-Cr-Mo based powdered material that is used for laser melting coating is characterized in that the weight percentage of each component of dusty material is:

Titanium valve: 10-18 %; Graphite carbon dust: 2-4.5 %; Niobium carbide powder: 6-15 %; Fe-Ni-Cr--molybdenum alloy powder: surplus; Wherein, the composition of Fe-Ni-Cr--molybdenum alloy powder is: nickel: 20-26%, chromium: 23-26%, molybdenum: 6-15%, iron: surplus.

2. the preparation method of the iron Ni-Cr-Mo based powdered material for laser melting coating claimed in claim 1 is characterized in that; Technique is as follows:

(1) presses the weight percentage of each component of powder, take by weighing various powder stocks;

The weight percentage of described each component of powder stock is: titanium valve: 10-18 %; Graphite carbon dust: 2-4.5 %; Niobium carbide powder: 6-15 %; Fe-Ni-Cr--molybdenum alloy powder: surplus;

It is dry that the various powder stocks that (2) will take by weighing are put into drying box, and the drying box temperature is 100-150 ℃, and be 2-3 hour drying time;

(3) utilize dry powder mixing equipment mixed-powder raw material, form mixed dusty material, mixing time is 3-5 hour;

(4) mixed dusty material is packed into Plastic Drum sealed storage.

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