CN107035412B - A low-inertia, fast-response metal-ceramic composite turbine shaft - Google Patents

Abstract

The invention discloses a low-inertia, fast-response metal-ceramic composite material turbine rotating shaft, which includes a turbine and a rotating shaft. The turbine is divided into a three-layer structure from the inside to the outside, which are the inner main body, the transition layer and the blade layer. The internal body is made of traditional nickel-based alloy steel, which is a uniform rotator manufactured by casting. The transition layer is superalloy powder, sintered to the inner body. The blade layer is made of silicon nitride and zirconia mixed ceramic material; the blade layer has the surface layer of the hub and the turbine blades arranged circumferentially on the outer wall of the wheel shaft. The rotating shaft is made of high temperature resistant steel, and one end is coaxially connected with the composite material wheel by hollow friction welding. The invention adopts nickel-based alloy steel-high temperature alloy powder-ceramic composite materials to reduce the quality of the turbine so that the turbine can withstand a high-temperature working environment of 1050°C, and the rotating shaft of the same material high-temperature resistant steel is connected by traditional friction welding technology. Reliable, low manufacturing cost, achieve the purpose of improving engine responsiveness.

Description

A low-inertia, fast-response metal-ceramic composite turbine shaft

technical field

The invention relates to the technical field of turbocharging, in particular to a low-inertia, fast-response metal-ceramic composite turbine rotating shaft of a turbocharger.

Background technique

The turbocharger is installed on the exhaust pipe of the engine, and the turbine casing is directly connected to the exhaust pipe. It is under high temperature and high pressure working conditions, especially in aviation piston engines and passenger car gasoline engines, where the exhaust temperature is as high as 950 °C ~1050°C, which is much higher than the maximum exhaust temperature of a diesel engine at 850°C, and the traditional nickel-based alloy turbine can no longer meet its performance requirements. Moreover, the density of the nickel-based alloy is high, and the mass of the turbine is heavy, which causes the response delay of the turbocharger to be obvious. Therefore, around the two major problems of high temperature resistance and low quality, a variety of supercharger turbines have been developed to solve the material, mainly two types: one is titanium aluminum alloy turbine; the other is ceramic turbine.

Titanium-aluminum alloy has excellent mechanical properties, low density, only 1/2 of nickel-based alloys, and still has good oxidation resistance and corrosion resistance when the temperature exceeds 600 °C. The turbocharger replaces the nickel-based alloy turbine with a titanium-aluminum turbine, which can effectively reduce the mass of the turbine, reduce the inertia of the turbine rotor, weaken the response lag of the turbine shaft, and improve the engine power response. However, like nickel-based alloys, titanium-aluminum turbines are only suitable for engine exhaust temperatures below 850°C, and their application to gasoline engines is limited.

Due to the advantages of high temperature resistance, corrosion resistance and wear resistance, ceramics can fully adapt to the high temperature working environment of the turbine, and can replace the traditional turbine material nickel-based alloy, becoming an ideal material for making turbocharger turbine rotors. In particular, silicon nitride ceramics have the advantage of low density compared to nickel-based alloys. The density of ceramic turbines is only 0.4 times that of nickel-based alloys, which can effectively reduce the mass of the turbine, reduce the inertia of the turbine rotor, and weaken the response lag of the turbine shaft. Improved engine power responsiveness. Patent CN201480023248 also provides a process method of "additive manufacturing of ceramic turbine parts bonded by partial instantaneous liquid phase using metal adhesive". However, the application of ceramic turbines is mainly restricted by two aspects: one is that due to its high brittleness and low ductility, it faces the problem of thermal shock damage under extremely harsh service conditions, and the formed thermal shock damage is in the structure under long-term high temperature and responsible load Due to the problems of evolutionary damage and sharp performance attenuation, the reliability of silicon nitride turbine rotors is severely challenged. On the other hand, due to its high melting point, the connection between the silicon nitride ceramic turbine and the high-temperature steel 42CrMo shaft has become a major problem restricting its application.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies in the above-mentioned prior art, and provide a low-inertia, fast-response metal-ceramic composite material turbine shaft. The quality of the turbine is reduced so that the turbine can withstand a high temperature working environment of 1050°C. The traditional friction welding process is adopted with the rotating shaft of the same material and high temperature resistant steel, which is reliable in connection and low in manufacturing cost, achieving the purpose of improving the responsiveness of the engine.

A low-inertia, fast-response metal-ceramic composite material turbine shaft, characterized in that: the turbine and the shaft are welded;

The turbine is divided into a three-layer structure from the inside to the outside, which are the inner main body, the transition layer and the blade layer; wherein, the inner main body is made of traditional nickel-based alloy steel, which is a uniform rotator manufactured by casting; the nickel-based alloy steel Nickel-based alloy steel K418 is selected; the transition layer is made of superalloy powder, which is sintered to the inner body; the blade layer is made of silicon nitride and zirconia mixed ceramic materials; the blade layer has the hub surface layer and the turbine blades arranged circumferentially on the outer wall of the wheel shaft; The rotating shaft is made of high temperature resistant steel, the material is 42CrMo, and one end is coaxially connected with the composite material wheel by hollow friction welding.

The advantages of the present invention are:

(1) The low-inertia, fast-response metal-ceramic composite turbine shaft of the present invention is made of nickel-based alloy steel-superalloy powder-ceramic composite material, which has light weight, low inertia, and improves the transient response of the turbocharger The advantages.

(2) The low-inertia, fast-response metal-ceramic composite turbine rotating shaft of the present invention adopts a nickel-based alloy steel-superalloy powder-ceramic composite turbine, which has the advantages of high temperature resistance and corrosion resistance;

(3) The low-inertia, fast-response metal-ceramic composite turbine shaft of the present invention adopts nickel-based alloy steel-superalloy powder-ceramic composite material turbine, and the hollow friction welding process of nickel-based alloy steel K418 in the middle body of the turbine and the rotating shaft 42CrMo is mature and reliable , to solve the problem of difficult connection between the pure ceramic turbine and the shaft.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the turbine shaft of the present invention.

Fig. 2 is a cross-sectional view of the structure of the turbine part of the present invention.

In the picture:

1-turbine 2-rotating shaft 101-inner body 102-transition layer

103-blade layer 102a-annular groove 102b-annular step 103a-hub surface

103b-turbine blade

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

The low-inertia, fast-response metal-ceramic composite turbine shaft includes two parts welded by a composite turbine 1 and a high-temperature-resistant steel shaft 2, as shown in FIG. 1 .

The composite material turbine 1 is divided into a three-layer structure from the inside to the outside, which are respectively an inner body 101 , a transition layer 102 and a blade layer 103 , as shown in FIG. 2 . Wherein, the inner body 101 is made of traditional nickel-based alloy steel, which is a uniform rotator manufactured by casting. Specifically: the nickel-based alloy steel is nickel-based alloy steel K418, with a density of 8.0kg/cm^3, a linear expansion coefficient of 12.6e-6/°C, a thermal conductivity of 10.15W/m.°C, and a heat resistance of 800°C.

The transition layer 102 is a superalloy powder sintered to the inner body. Before sintering, the transition layer 102 is positioned through the annular groove 101a designed in the circumferential direction of the inner body 101 and the annular step 101b structure designed in the circumferential direction of the front end, and the end of the inner body 101 has a part that does not cover the transition layer 102, thus, through The annular groove 101a prevents the transition layer 102 from deforming, and the transition layer 101a has a uniform thickness through the annular step 101b structure, preventing the transition layer 102 from cracking. Specifically: the material of the transition layer 102 is DOS superalloy powder, which is based on martensitic steel and ferritic steel. It is an ideal nuclear cladding material that can withstand high neutron flux. Due to its own crystal structure , the steel matrix at the center of the volume cube can form a diffused Coriolis gas cluster, forming an ultra-stable strengthened state, which has the characteristics of high temperature creep resistance. The material properties of the transition layer 102 are between K418 and ceramics, which plays a good transitional role and effectively avoids failure problems such as cracks on the ceramic surface caused by differences in linear expansion coefficients.

The blade layer 103 is made of silicon nitride and zirconia mixed ceramic material. Specifically: the density of silicon nitride and zirconia mixed ceramic material is 3.2kg/cm^3, the coefficient of linear expansion is 3.2e-6/℃, the thermal conductivity is 29.3W/m.℃, and the heat resistance is 1000℃; and the high temperature exceeds 900℃ When the gas passes through the surface of the composite material turbine of the present invention, the oxidation resistance and corrosion resistance of the ceramic coating are still good, and the temperature transmitted to the internal body drops below 700°C, which meets the heat resistance limit of K418 and also has good mechanical properties. The blade layer 103 has a hub surface layer 103a and turbine blades 103b arranged circumferentially on the outer wall of the wheel shaft. The thickness of the hub surface layer 103a is 1-3 mm. The turbine blades 103b are all made of silicon nitride and zirconia mixed ceramic materials, which are made by instant liquid phase bonding technology. , its density is only 0.4 times that of nickel-based alloys, which can reduce the total mass of the turbine by about 40%, and greatly reduce the mass radius of the turbine's rotational inertia, which is conducive to reducing the rotational inertia of the turbine shaft and improving its transient response.

The material of the high-temperature-resistant steel shaft 2 is 42CrMo, and one end is coaxially connected with the composite material turbine 1 by hollow friction welding method 3. The welding is reliable, and the problem of high brittleness of the simple ceramic turbine and difficult connection with the shaft is solved.

The low-inertia, fast-response metal-ceramic composite turbine shaft of the present invention is formed through the following steps:

Step 1: casting the inner body 101;

a. The investment casting process is adopted, and the low-temperature wax CP200 is selected as the investment material, and the wax mold of the internal main body is formed by standing for dewatering treatment.

b. Using silica sol adhesive to pour the internal main body wax mold, the process is coating, sanding and drying; wherein, the coating is made by mixing powder and silica sol in a certain proportion, including surface coating and transition coating and backcoat. The surface coating is in contact with the molten metal and does not react with the molten metal to ensure the quality of the inner surface of the mold shell, and 70 mesh zircon sand is used as the surface layer for sanding; the transition layer coating is sanded with 30-60 mesh coal gangue; the back layer Coal gangue powder of 270-320 mesh is used as the powder of the coating, and the refractoriness is greater than 1450°C to ensure the strength of the mold shell at high and low temperatures, the non-deformation and dimensional accuracy of the casting, and the sand is 16-24 mesh gangue; finally, the sealing is completed.

The mixing ratio of powder and silica sol for the above top coat is 3.7:1. The mixing ratio of powder and silica sol for transitional coating is 2.0:1. The mixing ratio of powder and silica sol for the back coat is 1.4:1. The content of the silica sol is mainly SiO ₂ : 30-31% (mass percentage), Na ₂ O≤0.3% (mass percentage); density (25°C): 1.195-1.215g/cm ³ ; viscosity (20℃)≤7.0Pa.S×10 ^-1 ; PH value 8.5~10.0; average particle size 10~20nm; appearance: milky white translucent; stable period: one year.

The powders of the above surface coating and transition coating are both 325-mesh zircon powder, and the zircon powder contains the following components in mass percentage: ZrO ₂ content ≥ 65%, Fe ₂ O ₃ content ≤ 0.1%, TiO ₂ content ≤ 0.5%, P ₂ O ₅ content ≤ 0.1%, Al ₂ O ₃ content ≤ 0.3%, SiO ₂ content <33%; density 4.6-4.78g/cm ³ ; refractoriness >1500°C; hardness 7.5 Mo Hardness; coefficient of expansion: 4.6×10 ^-3 (l/°C).

c. Dewaxing the wax mold of the inner main body cast in step b to obtain the inner main body shell;

d. Roasting the internal theme formwork;

e. Alloy melting and pouring;

The austenitic heat-resistant cast steel is smelted through an intermediate frequency vacuum induction furnace, and the inner main formwork is poured by a vacuum casting process.

f. Shell vibration and shot blasting;

Step 2: Injection molding the transition layer 102 by superalloy powder.

Mix the DOS superalloy powder and the adhesive silica sol in a ratio of 1:1.5 by weight, stir for about 40 minutes to make a paste; then add it to the storage tank of the injection machine, and after standing for 30 minutes, put the paste Inject into the transition layer mold with the inner body 101, the mold needs to be preheated to 300°C, and pressurized; put the formed inner body and transition layer into a drying oven for finalization and drying, the temperature is 120°C-200°C, and the time is 24～30h.

Step 3: forming the blade layer 103 by instantaneous liquid phase bonding.

1) The starting powder is prepared by mixing ceramic powder and inorganic binder powder at a weight ratio of 1:1.5; the ceramic powder is a mixed ceramic powder of silicon nitride and zirconia; the inorganic binder powder is metal powder.

2) Forming the blade layer 103 from the starting powder on the transition layer 102 using an additive manufacturing process. The additive manufacturing process may adopt one of direct laser sintering, direct laser melting, selective laser sintering, selective laser melting or electron beam melting.

3) Partial instantaneous liquid phase sintering is used to densify the formed blade layer.

Step 4: Friction welding of turbine 1 and shaft 2.

The welding parameters are slightly different for different diameters of the shaft 2. For a turbine shaft with a diameter of about 19mm, the welding speed is 850rpm, the upsetting pressure is 2.2-2.4MPa, the pressure needs to be maintained for 10s, and then tempering is required. The tempering temperature is 200°C , time 30s.

Claims (7)

1. the ceramic-metal composite turbine shaft of a kind of low inertia, quick response, it is characterised in that: including turbine and shaft Two parts are welded；

The turbine is divided into three-decker, respectively inside subject, transition zone and blade layer from the inside to the outside；Wherein, inside subject Using traditional Nickel-Based Steel, for the uniform revolving body manufactured by casting and molding method；Transition zone uses DOS high temperature alloy powder End is based on the basis of martensite steel and ferritic steel, a kind of ideal core involucrum with receiving highneutronflux of formation Material, due to the crystal structure of itself, the steel matrix at body cube center can form the Ke Shi gas group with disperse, transition zone Material property circle is sintered in inside subject between K418 and ceramics；Blade layer uses silicon nitride and zirconium oxide hybrid ceramic Material；Blade layer has the turbo blade of wheel hub surface layer and wheel shaft outer wall circumferential array；Blade layer is bonded using transient liquid phase Molding, the specific steps are as follows:

1) ceramic powders are mixed by weight 1: 1.5 with inorganic binder powder to prepare initial powder；

2) using increasing material manufacturing technique by initial powder the formed blades layer on transition zone；

3) it is sintered using partial transient liquid phase densify molding blade layer；

Described shaft one end is coaxially connected using hollow friction welding mode with turbine.

2. the ceramic-metal composite turbine shaft of a kind of low inertia as described in claim 1, quick response, feature exist Nickel-Based Steel K418, density 8.0kg/cm^3 are selected in: Nickel-Based Steel, 12.6e-6/ DEG C of linear expansion coefficient, thermal conductivity 10.15W/m. DEG C, 800 DEG C of heat resistance.

3. the ceramic-metal composite turbine shaft of a kind of low inertia as described in claim 1, quick response, feature exist In: silicon nitride and zirconium oxide hybrid ceramic density of material 3.2kg/cm^3,3.2e-6/ DEG C of linear expansion coefficient, thermal conductivity 29.3W/ M. DEG C, 1000 DEG C of heat resistance.

4. the ceramic-metal composite turbine shaft of a kind of low inertia as described in claim 1, quick response, feature exist In: rotating shaft material 42CrMo.

5. the ceramic-metal composite turbine shaft of a kind of low inertia as described in claim 1, quick response, feature exist In: the forging type of inside subject are as follows:

A, it using solvent casting technique, selects low-temperature wax CP200 as expendable pattern material, stands and remove water process, shaped inner main body Wax-pattern；

B, inside subject wax-pattern is poured using silica solution bonding agent system, technical process be coat, stucco and drying；

C, it dewaxes to the inside subject wax-pattern fusible pattern after being poured in step b, obtains inside subject formwork；

D, inside subject formwork is roasted；

E, alloy melting, and it is poured main body formwork；

F, shake shell and the clear shell of ball blast.

6. the ceramic-metal composite turbine shaft of a kind of low inertia as claimed in claim 5, quick response, feature exist In: in step b: coating is mixed by powder and silica solution, including investment precoat, transition coating and backing layer coating；Surface layer Coating is using 70 mesh zircon sands as surface layer stucco；Transition coating uses 30~60 mesh gangue stuccos；Backing layer coating uses 16~24 mesh gangue stuccos；The powder and silica solution mixed proportion of investment precoat are 3.7: 1；The powder and silicon of transition coating Colloidal sol mixed proportion is 2.0: 1；The powder and silica solution mixed proportion of backing layer coating are 1.4: 1；Investment precoat and transition zone apply The powder of material is 325 mesh zirconium English powder；The powder of backing layer coating uses the coal gangue powder of 270~320 mesh, and refractoriness is greater than 1450 ℃。

7. the ceramic-metal composite turbine shaft of a kind of low inertia as described in claim 1, quick response, feature exist In: transition zone is injection moulded by superalloy powder；

DOS superalloy powder and bonding agent silica solution are matched by weight 1: 1.5 ratio, after stir about 40min Paste is made；Then it is added in injector holding vessel, after standing 30min, paste injection is had to the transition of inside subject In layer mold, mold need to be preheated to 300 DEG C, extrusion forming；It is default that the inside subject of forming and transition zone are put into drying oven Type is dry, and 120 DEG C~200 DEG C of temperature, 24~30h of time.