usepowder metallurgyPorous, semi dense orFully dense material(including products).Powder metallurgy materials have unique chemical composition and physical properties that cannot be obtained by traditional melting and casting processesmechanical property , such as materialporosityControllable, uniform material structure, noMacrosegregation(After solidification of the alloy, different parts of its cross section are not caused by the macro flow of liquid alloychemical compositionNon-uniformity), canOne time formingEtc.
①Powder metallurgy antifriction material。Also called sinteringAntifriction material。It is prepared by dipping lubricating oil in the material pores or adding friction reducing agent or solid lubricant to the material composition.Between material surfacesfriction coefficientSmall, long service life and high reliability under limited lubricating oil conditions;At workFriction conditionNext, depending on the lubricant contained in itself or the surface layer, it has a self-lubricating effect.It is widely used to manufacture bearings, support bushings or face seals.
②Powder metallurgy porous material。It is also called porous sintering material.Made of spherical or irregularly shaped metal oralloy powder It is formed and sintered.The internal channels of the material are crisscross and interconnected, generally 30%~60% in volumeporosity, aperture 1~100 μ m.Good permeability, heat conduction and conductivity, high and low temperature resistance, thermal shock resistance and medium corrosion resistance.For manufacturing filtersPorous electrode、Fire extinguishing device, antifreeze device, etc.
⑥ Powder metallurgy electromagnetic materials.includeElectrical materialsandmagnetic material 。Among the electrical materials, the powder metallurgy materials used as power head materials include precious metals such as gold, silver and platinum, and the addition of tungsten, nickel, ironTungsten carbide, graphite and other powder metallurgy materials;Used as electrodeTungsten copper, tungsten nickel copper and other powder metallurgy materials;be used asbrushThere are metal graphite powder metallurgy materials;be used asElectrothermal alloyandThermocoupleThere are molybdenum, tantalum, tungsten and other powder metallurgy materials.
⑦ Powder metallurgyHigh-temperature material。includePowder metallurgy superalloy, refractory metals and alloyscermet, dispersion strengthening and fiber strengthening materials, etc.Used to manufacture turbine disks for use at high temperaturesinjector, blades and other high temperature resistant parts.
A powder metallurgy material consisting of a metal or alloy matrix phase and a highly dispersed metal or non-metallic phase that is essentially insoluble in the matrix.Its main characteristics are high temperature strength and good creep resistance.Strengthening mechanism andPrecipitation strengtheningsimilar.However, when the precipitation strengthening alloy is heated above the precipitation phase generation temperature, the precipitation phase will coarsen and re dissolve, so the use temperature is limited.
andDispersion strengtheningAlloy,Dispersion phaseIt can be stabilized to the solidus temperature of the matrix.The existence of dispersed particles changes theyield strength、Work hardeningCreep and fracture behavior.High temperature strength, especiallyCreep rateIt is affected by the geometric parameters of the dispersed phase (i.e. the spacing between particles in the matrix, the diameter of particles, and the shape (length width ratio)).
Modern Powder Metallurgy Technology
Its mechanism isdislocationThe influence of bypassing the second phase is also affected bygrain boundaryThere is no universally accepted creep model for the effect of slip.The general principle for the selection of dispersion phase is: high free energy of formation, high melting point, and nomutually dissolvable，Phase boundaryLow energy (good interface bonding), etc.The dispersion phase is usuallyoxide, or it can be stableIntermetallic compound, evenPure metal。
Typical materials
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Sintered aluminium powder
useSurface oxidation methodmanufacture.SAP has high high temperature strength and creep resistance, and its use temperature is up to 500 ℃, which is far superior to ordinary aluminum alloys.It is mainly used for:reactorInnuclear fuelCovers,Aircraft wingAnd fuselage,Compressor impeller, high-temperature piston, etc.
The earliest dispersion strengtheningNickel base alloyIt is ThO2 (2%) strengthened nickel (TD Ni).GeneralCoprecipitationLegal system.Ni strengthened by Th02 is also used for the wet process-Mo、Ni-Co、Ni-Cr-Al and other alloys.Mechanical alloyingAfter its emergence, a series of nickel based, iron based andCobalt base alloy。More than 10 have been used.The dispersion phase is generally ThO2 and Y203.Several typical alloys are listed in the table.
MA754 has better properties than ThO2 Ni Cr and has been successfully used asJet engineBlades.MA956E is a Fe Cr Al based material with superiorOxidation resistanceAnd corrosion resistance.MA6000E alloy, 1000hFracture stressAbove 800OC, it is far superior to TD Ni and IN792.
Powder metallurgy structural parts
At 1100 ℃, the 1000h fracture stress of TD Ni and IN792 is only 20-30MPa, while that of MA6000E is 160MPa.Therefore, MA6000E is a good blade material.
other
For example: dispersion strengtheninglead(DS-Pb) is the only example similar to SAP, and the dispersion phase is PbO, which is mainly used forsound fadeChemical appliances, radiation shielding and batteries;Aluminousmagnesium alloy(Both aluminum and zirconium are soluble in magnesium, but A1Zr4 dispersed phase is precipitated after dissolution);Intermetallic compoundFeAl3, FeNiAl9 strengthened Al Fe alloy, etc.
aviationAerospace industryThe more important powder metallurgy materials used in are brake pad materials, porous materials and high-strength powder alloys.
Brake pads
The brake pads are aircraftWheelBraking deviceThe core of.The landing speed of modern aircraft is more than 200 km/h, the brake load is very large, the instantaneous temperature of the brake pad surface can reach 800~1000 ° C, and no bonding is allowed, so as to avoid tire burst caused by brake failure.With iron powder orcopper powderThe powder metallurgy brake pads made of non-metallic powders added to the main components to prevent friction and adhesion can meet this requirement.
Powder metallurgy structural parts
mostMilitary aircraftandCivil aircraftAll adopt powder metallurgy brake pads.Because each brake will be worn, and the brake pad needs to be replaced after 100~500 times, it is the largest powder metallurgy material used on the aircraft.Powder metallurgy material
Some modern aircraft engines have been forgedPowder superalloyTurbine disk andcompressorDisc.In order to save raw materials and eliminate forging process, hot isostatic pressing can also be carried out directlyPrecision forming。useMechanical alloyingDispersion strengthened superalloy andRapid solidificationThe strength of powder superalloy above 1000~1050 ° C can exceed that of directionally solidified alloyGuide vaneandturbine blade Good materials.Powder aluminum alloyIt is mainly used as structural material of aircraft and engine.
The strength of mechanically alloyed aluminum alloy and rapidly solidified powder aluminum alloy can reach 700 MPa (about 70 kgf/mm).specific strengthReach titanium alloy andUltra high strength steelThe application temperature can reach 250~300 ° C, expanding the application range of existing aluminum alloys.Rapidly solidified aluminum lithium alloy andWrought aluminium alloycomparison,Specific stiffnessIt is 30% higher and twice the specific strength. If it replaces aluminum alloy, it can reduce the weight of aircraft by more than 30%.
