CN103537702B - The preparation method of high-flexural strength nano WC-Co alloy powder and WC-Co alloy product - Google Patents
The preparation method of high-flexural strength nano WC-Co alloy powder and WC-Co alloy product Download PDFInfo
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Abstract
The present invention relates to a kind of preparation method of high-flexural strength nano WC-Co alloy powder, the method is: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder.The invention also discloses the preparation method of WC-Co alloy product.The stage of WC-Co alloy powder is prepared at high-energy ball milling; prepare burden under vacuum; under the protection of argon gas, carrying out wet-milling by adding a certain amount of alcohol as liquid medium, effectively can prevent Powder Oxidation, improving uniformity and the dispersiveness of powdered ingredients.By adding oxide nano rare earth modification, suppressing growing up of the crystal grain of WC-Co hard alloy material, greatly improving Cemented Carbide Properties.
Description
Technical field:
The present invention relates to Hardmetal materials technical field, refer in particular to a kind of preparation method of high-flexural strength nano WC-Co alloy powder and the preparation method of WC-Co alloy product.
Background technology:
Carbide alloy forms composite carbide for hard phase with WC, TiC or the two, take Co as Binder Phase, by a kind of alloy material of powder metallurgical technique high-temperature liquid-phase sintering.Carbide alloy has that hardness is high, wear-resisting, intensity and a series of premium properties such as toughness is better, heat-resisting, corrosion-resistant, and particularly its high rigidity and wearability, even if also substantially remain unchanged at the temperature of 500 DEG C, still have very high hardness 1000 DEG C time.
When manufacturing carbide alloy, select raw material powder particle size between 1 ~ 2 micron, and purity is very high.Raw material is prepared burden in composition requirement ratio, adds alcohol or the wet-milling in wet ball mill of other media, makes them fully mix, pulverizes, drying, sieve after add the forming agent of class such as wax or glue, then through super-dry, sieve obtained compound.Mixture granulation, die mould, when being heated to close to binding metal fusing point (1300 ~ 1500 DEG C), sclerosis just forms eutectic alloy with binding metal.Through supercooling, in the grid that sclerosis Entropy density deviation form at binding metal, closely link together each other, form a firmly entirety.The hardness of carbide alloy depends on sclerosis phase content and crystallite size, and namely hardening, phase content is higher, crystal grain is thinner, then hardness is also larger.The toughness that junction temperature reduces carbide alloy is determined by binding metal, and binding metal content is higher, and bending strength is larger.
The preparation method that WC-Co hard alloy is traditional generates WC by W powder and C powder in 1400 ~ 1600 solid phase reactions, then with Co powder mixing and ball milling, cold moudling, densified finally by liquid-phase sintering.Generally at 1um ~ 10um, there is the problems such as fragility is large, work softening in the alloy grain that this preparation method obtains.Though adjustment WC/Co component can improve some performance of final part, such as, increase hardness increase wearability and corrosion resistance that WC content can improve part; Increase Co content can improve strength and toughness and improve processing characteristics.But be difficult to for a long time, while raising hardness, improve intensity and toughness always.
Carbide alloy has become its development trend from traditional to ultra-fine, nano level conversion at present, and in the more than ten years in the past, in high-performance carbide field, the research of ultra-fine cemented carbide and nanoscale carbide alloy is a hot issue always.But undue pursuit prepares nanometer or ultra-fine cemented carbide, cost is increased sharply, the effect obtained not is very obvious, and be difficult to control the grain growth in sintering process with this traditional handicraft production of powder metallurgy carbide alloy, cause the carbide alloy obtaining small grains very difficult.
At present, the production technology of the large complicated different in nature goods of carbide alloy mainly contains two kinds:
One is suppressed by compound, comprises mold pressing and cold isostatic compaction, then through oversintering, produce hard alloy blank, and sintering aft-loaded airfoil surplus is large especially, and difficulty of processing is large, length consuming time, extremely uneconomical; Another kind is contained in graphite jig by compound, suppresses and sinter one step completed heat pressing process.The feature of heat pressing process is that extrudate density is high, performance good, pressing pressure is little, can produces massive article.But the shape of goods is restricted, can only prepare the goods of simple shape, and this technique is only suitable for single-piece or small lot batch manufacture, productivity ratio is low, cost is high.Injection moulding is widely applied in the preparation of small size cemented carbide with complicated shape parts as a kind of near-net-shape technique, but injection molding technology also exists a lot of shortcoming, such as degumming tech is loaded down with trivial details, the percent defective that comes unstuck is high, product strength is low, and require higher to equipment and mold, fact proved that injection moulding can only prepare small size parts.
Gel casting (gelcasting) equals early 1990s invention by U.S. Oak Ridge National Laboratory professor M.A.Janney, is the solidify in place manufacturing process of a kind of complicated shape pottery or the metal parts near net-shape in recent years received much attention.Gel casting technology is the combination of conventional colloidal forming technology and chemical theory, compared with traditional wet-formed technique, there is the complicated shape that is easily shaped, large-scale part, die cost is cheap, shaping body composition is even, even density, defect is few, intensity is high, do not need special degreasing process, be applicable to the unique advantages such as various metals powder, the base substrate of what is more important gel casting can carry out common turnery processing, decrease the fine finishining amount of end article to greatest extent, for the precision form preparation of metallic article provides a kind of low cost, the process means of high reliability.
Summary of the invention:
The object of the invention is to overcome the deficiencies in the prior art part, a kind of preparation method of high-flexural strength nano WC-Co alloy powder and the preparation method of WC-Co alloy are provided.
The technical scheme that the present invention realizes the employing of its object is: a kind of preparation method of high-flexural strength nano WC-Co alloy powder, the method is: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder.
In the method, the weight of oxide nano rare earth is 1% of WC, Co grain weight amount.
In the method, the liquid-solid ratio of the alcohol added and original WC, Co powder (i.e. the ratio of the weight of alcohol and the weight of WC, Co powder) is 1:1.
In the method, the ratio of grinding media to material of grinding (i.e. the ratio of the weight of mill ball and the weight of WC, Co powder) is 10:1-12:1.
In the method, the rotating speed of ball milling is 180r/min-200r/min, and Ball-milling Time is 24h-48h.
The present invention also provides the WC-Co hard alloy production technology of a kind of preparation method based on above-mentioned high-flexural strength nano WC-Co alloy powder, and this production technology comprises:
A. vacuum strengthening grinding preparation WC-Co hard alloy powder: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder;
B. premixed liquid is prepared: by HEMA(hydroxyethyl methacrylate) be dissolved in toluene, be mixed with premixed liquid;
C. WC-Co alloy pulp is prepared: weigh high-flexural strength nano WC-Co cemented carbide powder and premixed liquid input ball mill mix and blend by certain solid content, and drop into appropriate dispersant;
D. mould molding: adopt gel injection-moulding equipment that the WC-Co alloy pulp prepared is injected silica gel mould, and add initator and catalyst, to control the slurry curing time when injecting;
E. the demoulding, drying, the shaping WC-Co hard alloy goods of low pressure sintering.
In above-mentioned production technology, during preparation WC-Co alloy pulp, better solid content is 50-60vol.%, and best solid content is 55vol.%, and best mixing time is 10h-12h.
In above-mentioned production technology, in described premixed liquid, the weight percentage of HEMA is 30%-40%, and the consumption of HEMA accounts for 1.7% of cemented carbide powder quality.
In above-mentioned production technology, described dispersant is hyper-dispersant Solsperse-6000, and content accounts for 0.3% of cemented carbide powder quality, and described initator is benzoyl peroxide (BPO), and its consumption is 0.7% of the consumption of HEMA.
In above-mentioned production technology, described low pressure sintering comprises following steps:
1. alloy base substrate is heated to 400 DEG C through 2h, dewaxes after insulation 1h;
2. make furnace temperature be elevated to 1320 DEG C with the speed of 10 DEG C/min, carry out solid-phase sintering, sintering time is 40min;
3. be heated to more than liquidus temperature and carry out liquid-phase sintering, sintering time is also 40min;
4., after liquid-phase sintering, apply the pressure of 4.5MPa, pressure carrier is common pure Ar gas, and compression rate is 0.3MPa/min, is incubated 15min again after pressurization, and pressure remains to furnace temperature lower than less than 900 DEG C always;
5. finally cool, cooldown rate when temperature is more than 900 DEG C is 8 DEG C/min, and cooldown rate when temperature is below 900 DEG C is 10 DEG C/min.
The present invention is in the preparation technology preparing WC-Co alloy powder and WC-Co alloy product; the stage of WC-Co alloy powder is prepared at high-energy ball milling; prepare burden under vacuum; under the protection of argon gas, wet-milling is carried out by adding a certain amount of alcohol as liquid medium; effectively Powder Oxidation be can prevent, uniformity and the dispersiveness of powdered ingredients improved simultaneously.In this preparation method, can obtain BET powder size is 59.4rim, and specific surface is the nanometer WC-Co composite powder of 6.82m/g, and in powder, Co element is uniformly dispersed.And, by adding oxide nano rare earth modification, suppressing growing up of the crystal grain of WC-Co hard alloy material, greatly improving Cemented Carbide Properties.
Accompanying drawing illustrates:
Fig. 1 is preparation technology's flow chart of WC-Co hard alloy goods in the present invention;
Fig. 2-1 adopts oxide nano rare earth to WC-Co hard alloy powder modification effect contrast figure in the present invention;
Fig. 2-2 be in the present invention WC-Co alloy pulp viscosity with the change curve of shear rate and monomer concentration;
Fig. 2-3 be in the present invention content of monomer to the influence curve figure of dry base substrate intensity and sintered body fracture strength;
Fig. 2-4 is the influence curve figure of different dispersant to WC-Co alloy pulp viscosity;
Fig. 2-5 is the densogram of cemented carbide sintered body under different sintering temperature in the present invention;
Fig. 2-6 is the firmness change curve map of cemented carbide powder after different temperatures sintering in the present invention;
Detailed description of the invention:
Below in conjunction with specific embodiments and the drawings, the present invention is further described.
The preparation method of high-flexural strength nano WC-Co alloy powder of the present invention is: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder.
In the method, the liquid-solid ratio of the alcohol added and original WC, Co powder (i.e. the ratio of the weight of alcohol and the weight of WC, Co powder) is 1:1.In Process During High Energy Ball Milling, carrying out wet-milling by adding a certain amount of alcohol as liquid medium medium, effectively can prevent Powder Oxidation, improve uniformity and the dispersiveness of powdered ingredients simultaneously.Under wet-milling condition, the addition of liquid medium has a great impact the uniformity of ball-milled powder composition and dispersiveness.There is a critical condition in the addition of liquid alcohol medium and liquid-solid ratio, when liquid-solid ratio very little time, liquid fully can not soak each powder particle, and in ball grinding cylinder, viscosity of sludge is larger, viscosity flow resistance in mechanical milling process is comparatively large, and ball and feed liquid effective motion can not occur with the rotation of ball grinding cylinder; In addition, Elements C o has less density, and its effect of inertia is less, and Co powder can not mix fully with WC powder, and thus, powder can not be disperseed and refinement effectively.Along with liquid-solid ratio increases, viscosity of sludge reduces, and the viscosity flow resistance of ball and powder particles reduces, and liquid is also gradually evenly coated on powder particle surface and between ball and powder, forms the very thin liquid film of one deck.Liquid film can reduce on the one hand the direct contact of ball grinding cylinder effectively and the ball milling that produces is mingled with, and meanwhile, can stop the gathering of powder particle, the chemical composition now in powder is more even.Along with the further increase of liquid-solid ratio, now, liquid medium is too much. and the collision mean free path degree between powder particle increases, effective collision effect reduces greatly, meanwhile, the density contrast due to liquid medium and powder is excessive and produce two-phase laminated flow, causes powder can not Homogeneous phase mixing and refinement effectively.
When liquid-solid ratio is 1:1, in powder, the chemical composition of Co phase is closest to the mixing match of starting powder, and Co can be dispersed in WC powder preferably, and now mixed effect is best.
In the method, the ratio of grinding media to material of grinding (i.e. the ratio of the weight of mill ball and the weight of WC, Co powder) is 10:1-12:1.
The BET granularity of powder reduces with the increase of ratio of grinding media to material.When ratio of grinding media to material is 4:l, after ball milling, the BET granularity of powder is higher, for 103.4nm, along with ratio of grinding media to material increases, abrading-ball quantity in unit volume increases, in mechanical milling process, in the unit interval, the collision frequency of abrading-ball and powder particle increases, and the grinding area of abrading-ball to powder is added, and fragmentation and the thinning effect of powder obviously increase.When ratio of grinding media to material is 10:1, the fragmentation of powder and thinning effect are more remarkable, and now powder BET granularity is only 69.3nm.And ratio of grinding media to material between 10:1-12:1 time, fragmentation and the refinement trend of powder become mild, and when ratio of grinding media to material is 12:1, powder BET granularity is 67.8nm, this is because suitable ratio of grinding media to material can promote fragmentation and the thinning effect of powder.But, after increasing ratio of grinding media to material further, although add the collision opportunity of abrading-ball and powder particle in mechanical milling process, the process of increase powder fragmentation, tearing, because abrading-ball collision is too fierce, the rising of ball milling temperature certainly will be caused, add the cold welding of powder and the process of reply, make powder fragmentation be tending towards dynamic equilibrium with reply, make powder particle change of granularity little, in mechanical milling process, energy ezpenditure sharply increases simultaneously, and wearing and tearing and the consumption of abrading-ball increase, and are unfavorable for the carrying out of ball milling.Therefore, when best ratio of grinding media to material 12:1, fragmentation and the refinement of powder bestly can be promoted.
In the method, the rotating speed of ball milling is 180r/min-200r/min, and Ball-milling Time is 24h-48h.
Along with rotational speed of ball-mill increases, powder BET granularity reduces gradually.When rotating speed is at 140 ~ 160r/rain, powder BET granularity sharply declines, this is because under the speed of 140r/min ball milling, ball milling speed is lower, abrading-ball and powder are roll at the bottom of tank or simple translation substantially, enough centripetal force can not be produced abrading-ball and powder particles are taken up effectively do parabolic motion, thus reduce the process of powder fragmentation.And rotating speed is when rising to 160r/min. some abrading-ball does incomplete throwing in tank.Ball milling effect has clear improvement, therefore the decline of powder BET granularity is very fast.When rotating speed changes between 160 ~ 200r/min, abrading-ball all has throwing in various degree, the ratio that increase abrading-ball with rotating speed does parabolic motion increases. urge the thinning process of powder, the BET granularity of powder decreases: when rotational speed of ball-mill reaches 200r/min, abrading-ball is more effective does parabolic motion, the throwing that now abrading-ball is frequent and violent in tank, impact, powder is constantly torn, broken, make the further refinement of powder BET granularity, under this state, ball milling effect is better.If but improve rotating speed further, for abrading-ball and powder particle provide larger possibility along with spherical tank revolves round the sun, cause the decline of thinning effect.
In addition, the impact of Ball-milling Time.Powder BET granularity to ball milling 12h is higher, for 102.1nm, along with Ball-milling Time extends, powder BET granularity significantly declines, when after ball milling 36h, there is minimum (<60nm) in powder BET granularity, and when Ball-milling Time is long, the ET change of granularity of powder tends towards stability.This is because in suitable Ball-milling Time, along with the prolongation of Ball-milling Time, abrading-ball increases powder particle collision frequency, increases the thinning process of powder particle.And along with the further prolongation of Ball-milling Time, powder fining to a certain extent after, the refinement of particle and reunion trend towards dynamic equilibrium, and particle size trends towards limiting value.When Ball-milling Time is 48h, the BET granularity of powder is compared with ball milling 36h, and powder does not obtain further refinement.Simultaneously long Ball-milling Time can increase the degree that abrading-ball and grinding jar are worn and torn, and introduce more impurity, the performance of alloy has larger impact.Show that ball milling 36h is one of optimum condition of the ultra-fine or nanometer WC-Co composite powder of preparation.
To sum up, high-energy-milling parameter is very important to the nanometer WC-Co powder obtaining uniform composition.In the application, well suitedly prepare nanometer WC powder and nanometer WC-Co composite powder technological parameter is in this project vacuum Intensive ball mill: liquid-solid ratio is 1:l, ratio of grinding media to material is 10:1, rotational speed of ball-mill is 180-200r/min, Ball-milling Time is 36h.At the process conditions, can obtain BET powder size is 59.4rim, and specific surface is the nanometer WC-Co composite powder of 6.82m/g, and in powder, Co element is uniformly dispersed.
In the method, the weight of oxide nano rare earth is 1% of WC, Co grain weight amount.
Oxide nano rare earth can well fine and close being adsorbed in Hardmetal materials particle, thus well can carry out modification to WC-Co hard alloy material, lifting Cemented Carbide Properties, and its effect is mainly reflected in:
1. growing up of crystal grain is suppressed.In sintering process, WC particle mainly contains two kinds of growth patterns: one is noncontinuity growth, and another kind is continuity growth.
Noncontinuity growth and tiny hard phase WC contact with each other by crystal grain, and polymerization is grown up, and are unified into thick WC or thick WC annexes tiny WC.Add nano rare earth material modified after, now because the nano particle pinning of nanometer additive is in WC grain border, its aggregation growth is hindered, inhibits grain growth.Continuity grows, namely after in WC-Co hard alloy sintering process, liquid phase generates, the atom on solid phase WC particle surface is dissolved in liquid phase gradually, liquid phase has larger saturation solubility to WC granule, lower to the oarse-grained saturation solubility of WC, thus WC granule first dissolves, and separates out on large WC particle surface, so bulky grain WC is tending towards growing up, Os-wald growing mechanism can be regarded as.Add nano rare earth modifier and can stablize liquid phase in hard alloy sintering process, delay the precipitation of WC, like this when WC separates out from the state that degree of supersaturation is larger, WC grain forming core speed is far longer than growth rate, thus reaches the object of crystal grain thinning.
2. carbide alloy toughness is improved.WC is the skeleton of carbide alloy, and it is more abundant that refinement WC can make this skeleton contact, and then can bear larger load, nano rare earth modifier add the hardness that can improve prepared carbide alloy.Therefore after adding nano rare earth modifier, sample fracture toughness mean value is improved, and improves reason relevant with grain size, also relevant with intercrystalline strengthening, solution strengthening etc.Because crystal grain thinning makes crystal boundary greatly increase, because WC intensity is very large, more tiny crystal grain is conducive to the defect reducing single crystal grain, such fracture mainly occurs in crystal boundary, crackle is formed at crystal boundary and expands at crystal boundary, and simultaneously due to solution strengthening crystal boundary, the resistance of such Crack Extension increases, expansion need consume more multi-energy, therefore makes the toughness of Hardmetal materials be able to good raising.
Therefore, add nano rare earth as modification, hardness and fracture toughness can be improved simultaneously, reduce coefficient of friction and improve wearability.Find in test, the hard alloy wear resistance adding nano rare earth improves, and increasing along with nano rare earth addition, wear volume presents the trend first declining and raise afterwards.Due to nano rare earth addition little time, often do not reach crystal grain thinning, purification boundary, improve the effect of W, C solid solubility in Binder Phase.And add too much, then possibility segregation is on interface, reduces its mechanical property thus indirectly have impact on wearability.Namely there is an optimum value in nano rare earth addition, the too low or too high wearability that all can reduce carbide alloy.In the application, by oxide nano rare earth addition about 1% of WC, Co grain weight amount, optimum efficiency can be reached.
By aforementioned known, adopt vacuum to strengthen the WC-Co hard alloy powder of grinding preparation in the present invention, performance is splendid, prepares WC-Co hard alloy goods further on this basis.WC-Co hard alloy production technology comprises:
A. vacuum strengthening grinding preparation WC-Co hard alloy powder: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder;
B. premixed liquid is prepared: by HEMA(hydroxyethyl methacrylate) be dissolved in toluene, be mixed with premixed liquid;
C. WC-Co alloy pulp is prepared: weigh high-flexural strength nano WC-Co cemented carbide powder and premixed liquid input ball mill mix and blend by certain solid content, and drop into appropriate dispersant;
D. mould molding: adopt gel injection-moulding equipment that the WC-Co alloy pulp prepared is injected silica gel mould, and add initator and catalyst, to control the slurry curing time when injecting;
E. the demoulding, drying, the shaping WC-Co hard alloy goods of low pressure sintering.
In above-mentioned production technology, during preparation WC-Co alloy pulp, better solid content is 50-60vol.%, and best solid content is 55vol.%, and best mixing time is 10h-12h.In described premixed liquid, the weight percentage of HEMA is 30%-40%, and the consumption of HEMA accounts for 1.7% of cemented carbide powder quality.Described dispersant adopts hyper-dispersant Solsperse-6000, and content accounts for 0.3% of cemented carbide powder quality.
The key of the shaping of gel injection-moulding is that to prepare solid content high, good fluidity, the suspended nitride of good stability.The viscosity number of slurry when shear rate 20s-1 lower than 1Pas guarantee its fully not filling mould by when external force.As shown in Fig. 2-2, WC-Co alloy pulp viscosity is with the change curve of shear rate and monomer concentration.
The Forming Theory of gel injection-moulding is exactly rely on the polymerization of monomer in premixed liquid to connect to form a three-dimensional net structure metal dust to be wrapped in a inside formation overall structure.So the performance of content to end article of monomer is most important in premixed liquid.Content of monomer in premixed liquid is too low, namely the content of monomer in shaping base substrate is too low, will cause base substrate without intensity or intensity low, this is important is because too low content of monomer polymerization is by formation incomplete network structure, all powders can not be wrapped up completely, so cause blank strength low.In the mixed system of gel and powder, monomer connects coated metal powder, so a balance will be kept between content of monomer and the volume fraction of metal-powder, just there will be local monomer polymerization form organic matter caking when the content of monomer exceedes this equilibrium valve, have the place of caking to be formed after sintering inside that cavity remains in sintered body.
The key of content of monomer in the gel casting technique of carbide alloy, hydroxyethyl methacrylate (HEMA) is selected to be organic monomer in the present invention, because HEMA has hydroxyl-OH, in toluene, it can be adsorbed on the surface of the cemented carbide powder particle with water-wet behavior, serve as surfactant, improve the wetability of toluene and cemented carbide powder particle to a certain extent, powder particle is better disperseed, therefore the increase along with HEMA addition reduces by the viscosity of slurry.
As shown in Fig. 2-2, organic monomer content is higher, then the organic three-dimensional net structure formed after gel is more complete, and powder consolidation is more firm, and thus blank strength is also higher.Although increase the intensity that HEMA content is conducive to improving dry base substrate, also can find from Fig. 2-3, the fracture strength of sintered body when the content of HEMA is too much, can be caused to reduce.Therefore, the organic monomer of the best of the present invention and HEMA content are account for cemented carbide powder quality 1.7%.
Shown in composition graphs 2-4, dispersant selects and controls the solid content raising of addition to gel injection-moulding have great role.Dispersant of the present invention adopts hyper-dispersant Solsperse-6000, and content: 0.3wt%(accounts for the quality of formed powder); Compared with traditional dispersant, hyper-dispersant has following advantage: (1) forms multi-point-anchoring at particle surface, improves absorption fastness, not easily desorb; (2) carbon chain lengths of General Decentralized agent is at most containing 18 carbon, and the solvent chain of hyper-dispersant is than traditional dispersant lipophilic group regimental commander, can play effective Steric stabilization.
In above-mentioned production technology, described initator is benzoyl peroxide (BPO), and its consumption is 0.7% of the consumption of HEMA.
In gel casting, the addition of initator is the principal element affecting induction period.Induction period is exactly slip hardening time, and induction period is too short, and the experimental implementation time is short, can not well pour into a mould, and slurry well can not fill type; Induction period is long, and the easy sedimentation of the powder in slurry, can not ensure the uniformity of base substrate.In order to extend the hardening time of slurry, usually reduce the interpolation content of initator, but too low initator by cause slurry do not solidify or solidification intensity low.In gel casting hard alloy process, because article shape is complicated, so bring difficulty to the demoulding of goods, so the intensity of shaping base substrate must be ensured.The blank strength of goods and the content of initator have much relations, and along with the raising of initiator content, the intensity level of goods increases, so must select suitable amount of initiator, find the equalization point that of the hardening time of slurry and base substrate suitable.In the present invention, selection initator is benzoyl peroxide (BPO), and content: 0.7wt%(accounts for the quality of organic monomer), can well realize the controllable cured of slurry.
In above-mentioned production technology, described low pressure sintering comprises following steps:
1. alloy base substrate is heated to 400 DEG C through 2h, dewaxes after insulation 1h;
2. make furnace temperature be elevated to 1320 DEG C with the speed of 10 DEG C/min, carry out solid-phase sintering, sintering time is 40min;
3. be heated to more than liquidus temperature and carry out liquid-phase sintering, sintering time is also 40min;
4., after liquid-phase sintering, apply the pressure of 4.5MPa, pressure carrier is common pure Ar gas, and compression rate is 0.3MPa/min, is incubated 15min again after pressurization, and pressure remains to furnace temperature lower than less than 900 DEG C always;
5. finally cool, cooldown rate when temperature is more than 900 DEG C is 8 DEG C/min, and cooldown rate when temperature is below 900 DEG C is 10 DEG C/min.
In low pressure sintering, sintering temperature mainly has considerable influence to sintered body grain size, sintered density and sintered body hardness, is mainly reflected in:
(1) impact of sintering temperature on sintered body grain size found through experiments, and the crystal grain of WC is grown up along with the rising of sintering temperature.The main method solving grain growth in sintering process adds inhibitor, and the inhibitor that this project adopts is oxide nano rare earth, can well suppress growing up of crystal grain.In general, when sintering at a lower temperature, add a small amount of inhibitor and just can suppress growing up of WC grain; When sintering at a higher temperature, just must increase the addition of inhibitor, the discontinuous of crystal grain could be suppressed to grow up.In the present invention, when sintering at 1320 DEG C, the crystal grain of WC is more tiny, major part crystal grain is about 200nm, the phenomenon of individual crystalline grains abnormal growth is not had to occur, when sintering at 1400 DEG C, grain growth is to more than 2um, although the addition of inhibitor reaches 1.0%, the phenomenon of abnormal grain growth is also had to occur. therefore, can learn: along with the rising of sintering temperature, WC grain has the trend of growing up, also the discontinuous of crystal grain cannot be suppressed to grow up even if add sintering grain inhibitor, but when sintering at 1320 DEG C, tiny WC grain can be obtained.
(2) sintering temperature on the impact of sintered density in general, and along with the rising of sintering temperature, the density of sintered body can increase, and this is due to the rising along with temperature, and the liquid content in sintered body increases, and is conducive to the diffusive migration of material.Figure below 2-5 is the density of cemented carbide powder powder sintered compact under different sintering temperature, and from Fig. 2-5, along with the rising of sintering temperature, the density of sintered body is not increase, but diminishes gradually.By carrying out zero-G test to the sample after sintering, the sintered body weightlessness under discovery high temperature sintering is always greater than the weightlessness of the sintered body under low-temperature sintering, so the reason causing sintered density to decline along with the rising of sintering temperature is exactly the evaporation of Co.By known to the analysis of sintered density, the sintering temperature of 1320 DEG C is enough to make nanometer powder carbide alloy completely densified.
(3) sintering temperature on sintered body hardness to affect WC grain size less, the mean free path of Co phase is shorter, and the hardness of alloy is higher, but along with the rising of sintering temperature, WC grain size is grown up thereupon, and the hardness of carbide alloy can decline thereupon.From Fig. 2-6, when sintering temperature is lower than 1360 DEG C, the hardness of carbide alloy is all higher, and far away higher than conventional cemented carbide, 1320 DEG C time, the hardness of sintered body is maximum, reaches HRA94.6, this be conventional cemented carbide incomparable.When sintering temperature is higher than 1360 DEG C, the hardness of sintered body sharply declines, its hardness is almost suitable with conventional carbide alloy, this mainly because the evaporation of Co causes sintered body inside to occur hole, thus affects the hardness of sintered body, and WC grain is sharply grown up, its crystallite dimension is almost suitable with conventional cemented carbide, and WC grain size is larger, the mean free path of Co phase is longer, thus causes the hardness of alloy corresponding lower.Therefore, when sintering temperature is at 1320 DEG C, the hardness of sintered body is maximum.To sum up, the present invention adopts low pressure sintering mode to sinter base substrate, and sintering temperature is arranged on 1320 DEG C, can reach best sintering effect, ensures to obtain tiny WC grain, the highest hardness and good compactness.
In sum; the present invention is in the preparation technology preparing WC-Co alloy powder and WC-Co alloy product; the stage of WC-Co alloy powder is prepared at high-energy ball milling; prepare burden under vacuum; under the protection of argon gas, wet-milling is carried out by adding a certain amount of alcohol as liquid medium; effectively Powder Oxidation be can prevent, uniformity and the dispersiveness of powdered ingredients improved simultaneously.In this preparation method, can obtain BET powder size is 59.4rim, and specific surface is the nanometer WC-Co composite powder of 6.82m/g, and in powder, Co element is uniformly dispersed.And, by adding oxide nano rare earth modification, suppressing growing up of the crystal grain of WC-Co hard alloy material, greatly improving Cemented Carbide Properties.
Experimental data surface, is undertaken modified by adding oxide nano rare earth, and Cemented Carbide Hardness is than unmodified raising more than 30%, and coefficient of elasticity improves more than 10%, and Fracture Toughness improves more than 73%.The key technical indexes that the WC-Co hard alloy adopting the inventive method to prepare can reach is as follows:
(1) hart metal product is containing Co content 10%, and grain size 6 μm, density 14.4g/cm3, hardness is greater than 92.5HRA, and bending strength reaches 4000Mpa, and bending strength is high, and combination property is outstanding.
(2) by the hard metal article that gel casting process is made, key property be density at 11-15g/cm3, bending strength >=1270, hardness >=90HRA.
Claims (1)
1. based on the WC-Co hard alloy production technology of vacuum Intensive ball mill preparation method, it is characterized in that: this production technology comprises:
A. vacuum strengthening grinding preparation WC-Co hard alloy powder: under vacuum, the composition ratio of original WC, Co powder according to carbide alloy is prepared burden, using alcohol as ball milling liquid medium, protective gas during using argon gas as ball milling, adopt carbide alloy mill ball to carry out ball milling preparation, and add oxide nano rare earth in process of lapping; By drying, sieving obtains high-flexural strength nano WC-Co cemented carbide powder;
B. prepare premixed liquid: HEMA is dissolved in toluene, be mixed with premixed liquid;
C. WC-Co alloy pulp is prepared: weigh high-flexural strength nano WC-Co cemented carbide powder and premixed liquid input ball mill mix and blend by certain solid content, and drop into appropriate dispersant;
D. mould molding: adopt gel injection-moulding equipment that the WC-Co alloy pulp prepared is injected silica gel mould, and add initator and catalyst, to control the slurry curing time when injecting;
E. the demoulding, drying, the shaping WC-Co hard alloy goods of low pressure sintering;
In above-mentioned steps, during preparation WC-Co alloy pulp, solid content is 50-60vol.%, and mixing time is 10h-12h;
In described premixed liquid, the weight percentage of HEMA is 30%-40%, and the consumption of HEMA accounts for 1.7% of cemented carbide powder quality;
Described dispersant is hyper-dispersant Solsperse-6000, and content accounts for 0.3% of cemented carbide powder quality; Described initator is benzoyl peroxide, and its consumption is 0.7% of the consumption of HEMA
Described low pressure sintering comprises following steps:
1. alloy base substrate is heated to 400 DEG C through 2h, dewaxes after insulation 1h;
2. make furnace temperature be elevated to 1320 DEG C with the speed of 10 DEG C/min, carry out solid-phase sintering, sintering time is 40min;
3. be heated to more than liquidus temperature and carry out liquid-phase sintering, sintering time is also 40min;
4., after liquid-phase sintering, apply the pressure of 4.5MPa, pressure carrier is common pure Ar gas, and compression rate is 0.3MPa/min, is incubated 15min again after pressurization, and pressure remains to furnace temperature lower than 900 DEG C always;
5. finally cool, cooldown rate when temperature is more than 900 DEG C is 8 DEG C/min, and cooldown rate when temperature is below 900 DEG C is 10 DEG C/min.
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