CN1295377C - Process for producing metal carbonide hard face coating and application thereof - Google Patents

Abstract

The present invention relates to a method for preparing a metal carbide hard surface coating layer and applications thereof, which belongs to the technical field of chemical thermal processing of surfaces of steel and iron material. The present invention is characterized in that in molten borax salt bath, B4C powder is used to reduce flue dust (in which vanadium oxide, chromium oxide, titanium oxide or niobium oxide achieves 83% to 87%) from a ferroalloy work so as to generate a metal carbide (vanadium carbide, chromium carbide, titanium carbide or niobium carbide) is formed on a steel and iron base material piece which is heated in the salt bath. The coating layer is firmly bonded with base material; the thickness of the coating layer is 15 mu m to 25 mu m; the hardness of the coating layer is HV1600 to HV3200. The hard surface coating layer has the advantages of favorable abrasion resistance, corrosion resistance, prominent economic benefits, etc. The metal carbide hard surface coating layer which is prepared by the method of the present invention is especially suitable for being used as the hard surface coating layer of a work piece or component which has high requirements on abrasion resistance and corrosion resistance. The continuous working service life of the working piece which is provided with the hard surface coating layer is extended by one to eight times.

Description

A kind of method and application thereof for preparing metal carbonide hard face coating

Technical field:

The present invention relates to a kind of method and application thereof for preparing metal carbonide hard face coating, belong to the surface chemical and heat treatment technical field.

Background technology:

Since the high rigidity of carbide coating and good resistance to wearing and resistance to corrosion, and cause numerous investigators' interest, at first be that the researchist of Japan has reported with TD method (TD-processing) preparation metal-carbide coating, this method is at Na ₂B ₄O ₇In the molten salt bath, make for the vanadium agent preparation vanadium carbide coating with vanadium iron (or ferrochrome, ferrotianium, ferro-niobium) powdered alloy ^[1,2]Zhong Guo some investigator has also reported the VC coating with the preparation of TD method subsequently, and this coating technology is used for Mould Machining ^[3,4]But, author's the test according to the present invention, the TD method has some following shortcomings: (1) is because the long-range too salt bath of the proportion proportion of vanadium iron (or ferrochrome, ferrotianium and ferro-niobium) alloy, processed workpiece surface is stranded this ferro-vanadium powder and can not in salt bath, spares distribution, so can not obtain uniform coating; (2) fragmentation of the iron alloy of vanadium, chromium, titanium, niobium and grinding are very difficult; (3) ferroalloy powder of vanadium, chromium, titanium, niobium is easy to oxidation (under the high temperature), and along with the repetition of coating procedure, constantly collection is tired in salt bath for the oxide compound of vanadium and iron, and this can cause the fusing point and the viscosity increased of salt bath.Because above-mentioned shortcoming, to the eighties in 20th century, some Chinese investigator proposes the method that another prepares vanadium carbide coating again, and Here it is uses aluminum reduction V in molten salt bath ₂O ₅The preparation vanadium carbide coating ^[5,6,7]

Yet author's of the present invention test shows that it also is unfavorable being equipped with carbide coating with the aluminum reduction legal system.Therefore there is following shortcoming in method: (1) on the surface of molten salt bath, and aluminium powder is because of having high activity oxidation and fierce burning easily, so when aluminium powder is added into salt bath, can cause that operator's is dangerous; (2) because the scaling loss of aluminium powder causes the add-on of aluminium powder accurately not control; (3) along with the repetition of process, AL ₂O ₃Constantly accumulation in salt bath, this will cause the fusing point of salt bath and viscosity constantly to increase; (4) with the VC coating of aluminum reduction method preparation, its corrosion resistance and wear resistance are not as the height of TD method VC coating.

Reference:

[1] institute of Toyota central authorities: new well thoroughly, Tian Xingfu too: No. the 5th, " thermal treatment " (Japanese) the 18th volume, clear and in October, 53.

[2] No. the 2nd, saturating " thermal treatment " (Japanese) the 27th volume of new well, clear and in April, 62.

[3] Lei Tingquan: " 300 kinds of thermal treatment process " (M), China Machine Press (1993 years).

[4] Shi Zhanfu: " metal heat treatmet " No.6 (1986);

[5] Cui Chaoling, Wang Peijie, Hu Baozhang etc.: " metal heat treatmet " No.5 (1985).

[6] Lin Songzhen: " metal heat treatmet " No.8 (1988).

[7] first Yongxin, Li Musen, Xu Ying etc.: " metal heat treatmet " No.7 (1999).

[8] U.D.Veriadin, V.P.Mashirev.N.G.Riavtsev.etal: " HanebookofThermodynamicProperties of Inorganic substances " (M) ATOMIZDAT, Moscov. (1976) (the Russian edition).

[9]Wang Biao，Zhan Zi Hua，Yuan SengKong：“Proc on 5th Inter cong of Heat Treatment of Materials”，oct 1986 Budapest Hungary。

[10] Hui Weijun, Dong Han, Wang Maoqiu etc.: " metal heat treatmet " 2002 the 27th the 1st phases of volume.

Summary of the invention:

The objective of the invention is to overcome the above-mentioned shortcoming that TD method and aluminum reduction legal system are got carbide coating, proposed a kind of method for preparing carbide coating, promptly in the vitrified borax salt bath, use B ₄The C reducing metal oxide is prepared resistance to abrasion and the higher carbide coating of erosion resistance, and this method has B ₄C can not burn B when adding salt bath ₄C and oxide compound not segregation in salt bath, energy uniform distribution, and B ₄Advantages such as the C pulverizing and jevigating is easy, the life cycle of salt bath is long.The hard-surface coating of this method preparation is especially suitable for use as the hard-surface coating of resistance to abrasion and demanding workpiece of erosion resistance or member.

The method of production of the present invention and test and principle: in the borax salt bath, use B ₄C reduces V ₂O ₅(or Cr ₂O ₃Or TiO ₂Or Nb ₂O ₅) form metal carbonide hard face coating mechanism as follows: at first be by following reaction, in salt bath, form active vanadium (or chromium, titanium, niobium) atom:

………………(1)

………………(2)

………………………(3)(M＝V.Cr.Ti.Nb)

………………………(4)(M＝V.Cr.Ti.Nb)

According to the relation of free energy among Fig. 1 and temperature as can be known: in the temperature range of 300-2500K, because of (Δ G) arranged ⁰ _B2O3＜(Δ G) ⁰ _V2O5(Δ G) ⁰ _B2O3＜(Δ G) ⁰ _Cr2O3, and (Δ G) ⁰ _B3O3＜(Δ G) ⁰ _Nb2O5, therefore in salt bath, B is arranged ₄C and V ₂O ₅(or Cr ₂O ₃Or Nb ₂O ₅) when existing, reaction (2) and (3) is to carry out and form active vanadium atom or chromium niobium atom to the right.Simultaneously, in temperature is the scope of 1500-2500K.Because of (Δ G) arranged ⁰ _B2O3＜(Δ G) ⁰ _TiO2, therefore in salt bath, B is arranged ₄C and TiO ₂When existing, reaction (2) and (3) can be carried out to the right.In addition, it can also be seen that, when temperature is higher than 12500K, because of (Δ G) arranged from Fig. 1 ⁰ _CO2(Δ G) ⁰ _V2O5, therefore reaction (4) also can be carried out to the right when M=V.

Secondly, reactive metal (vanadium, chromium, titanium, the niobium) atom that is generated by above-mentioned reaction combines by the surface adsorption of steel mother metal and with the carbon atom that outwards diffuses out in the steel of base metal, forms the nucleus of metallic carbide, this nucleus is grown up along with the progress of process, and forms carbide coating.Can think: because larger-size vanadium atom is difficult to internal diffusion, and the less carbon atom of size passes established VC coating easily and to external diffusion, so the VC coating is surperficial abducent from the steel mother metal.Cr ₃C ₂, the formation mechanism of TiC or NbC coating and VC coating mechanism similar.

The preparation method of metal carbonide hard face coating of the present invention is: in the molten salt bath of being made up of 85% heavy industrial borax and 15% industrial Sodium Fluoride heavily, use technical pure B ₄The C powder, reduction contains ferroalloy works' flue dust of 83-87% metal oxide respectively, and the metal oxide in the flue dust is V ₂O ₅Or Cr ₂O ₃Or TiO ₂Or Nb ₂O ₅, in salt bath on the heated iron and steel mother metal, obtain hardness and reach HV1600～3200, thickness be 15-22 μ m contain VC or Cr ₃C ₂Or the hard-surface coating of TiC or NbC; Wherein:

1.1, the reductive agent that forms carbide coating is technical pure B ₄The C powder, B ₄The C powder size is less than 60 orders;

1.2, the processing condition of metal-carbide coating are; Workpiece is heated to temperature 920-950 ℃, be incubated after 6-8 hour, the temperature of salt bath adjusted to steel of base metal is quenched under the necessary austenite transformation temperature, look workpiece and vary in size, kept 5 to 15 minutes, then workpiece is taken out from salt bath and the oil of quenching in, treat that workpiece cools off in oil after, put into boiling water and boil, remove the salt bath residue on the workpiece, then, again workpiece is put into the box-type furnace tempering; If steel of base metal is a carbon content less than in 0.9% or soft steel, then steel of base metal needs through carburizing in advance, to guarantee to form the required carbon content of carbide;

1.3, B ₄C powder and oxidiferous flue dust constitute the active additive of preparation metal-carbide coating, the add-on that forms the required active additive of metal-carbide coating is: the add-on of metal oxide be the borax fusion salt bath heavy 10%, the content of metal oxide in the add-on of flue dust=10% salt bath weight/flue dust; B ₄The C add-on is difference with the difference of producing the carbide coating kind, when the coating of producing is respectively VC, Cr ₃C ₂, when NbC and TiC, B ₄The add-on of C is respectively 17.0%, 16.6%, 15.5% and 20.7%.

Metal carbonide hard face coating of the present invention is as the hard-surface coating of resistance to abrasion and demanding workpiece of erosion resistance or member.

Implementation process of the present invention is:

1, the composition of blank salt bath

Blank salt bath consist of Na ₂B ₄O ₇: NaF=85%: 15% (weight).B ₄C powder and contain vanadium or contain chromium or titaniferous or the powder of oxide compound between 83-87% that contain niobium can be used as the active additive that forms metal-carbide coating.In the method for the present invention, both can use to contain vanadium or contain chromium or titaniferous or the Industrial Metal oxide compound that contains niobium are made the metal-carbide coating active additive, also can use respectively: the flue dust from ferro-vanadium factory is made V ₂O ₅Surrogate, with the flue dust of producing ferrochrome as Cr ₂O ₃Surrogate, make Nb with the flue dust of producing ferro-niobium or ferro-titanium ₂O ₅Or TiO ₂Surrogate, make the metal-carbide coating active additive.The embodiment of the invention is all used the surrogate of making metal oxide from the flue dust of ferroalloy works.

2, the add-on of metal-carbide coating active additive

According to Theoretical Calculation and experiment experience, the add-on of active metal oxide is 10% of a blank salt bath gross weight, if activating oxide is V ₂O ₅, B then ₄The add-on of C powder is V ₂O ₅17% of dosage.If activating oxide is Cr ₂O ₃, B then ₄The C dosage is Cr ₂O ₃16.6% of dosage.If activating oxide is Nb ₂O ₅, B then ₄The C dosage is Nb ₂O ₅15.5%.If activating oxide is TiO ₂, B then ₄The C dosage is TiO ₂20.7%.

Use when making the surrogate of oxide compound from the flue dust of ferroalloy works, the add-on of flue dust need convert by oxide content in the flue dust.That is: the flue dust of ferro-vanadium production contains V ₂O ₅Be 86.4%, then contain V ₂O ₅The add-on of flue dust should be 10% heavy/0.864=11.58% of blank salt bath.The flue dust of ferrochrome exothermic contains Cr ₂O ₃Be 85.2%, then the flue dust dosage is 10% heavy/0.852=11.74% of blank salt bath; And the flue dust in the ferrotianium production contains TiO ₂Be 84.7%, then the add-on of flue dust should be 10% heavy/0.847=11.81% of blank salt bath.Ferrocolumbium flue dust contains Nb ₂O ₅Be 82.9%, then the flue dust dosage is 10% heavy/0.82.9=12.1% of blank salt bath.

3, the schedule of operation of preparation carbide coating

Be to save cost, the present invention adopts from the flue dust of the ferroalloy works surrogate as metal oxide.

At first, each composition of above-mentioned blank salt bath is mixed, and in the stainless steel crucible, melt, then oxidiferous flue dust and B ₄The C powder mixes, and join in the blank salt of fused, and stirring makes the salt bath homogenizing, be heated to 920 to 950 ℃ temperature when salt bath after, workpiece through polishing and preheating is joined in the salt bath, and 920 to 950 ℃ of maintenances 6-8 hour, then the temperature of salt bath being adjusted to quenches under the necessary austenite transformation temperature steel of base metal, and keep 5 to 15 minutes (deciding) on workpiece size, then workpiece is taken out from salt bath and the oil of quenching in, treat that workpiece cools off in oil after, put into boiling water and boil, so that the salt bath residue on the removing workpiece, then, again workpiece is put into the box-type furnace tempering, can make and obtain thickness on the heated iron and steel mother metal in salt bath is 15-22 μ m, hardness is the metal carbonide hard face layer of HV1600-3200.

Beneficial effect of the present invention:

Its non-stop run life-span of workpiece that the present invention has abrasion resistance and erosion resistance height, handled with the present invention is improved 1-8 doubly, advantages such as remarkable in economical benefits.

B ₄The C reduction method is produced the reduction temperature of metal-carbide coating and soaking time has decisive influence to the thickness of coating, and table 1 and table 2 provide respectively uses B ₄The temperature and time of C reduced oxide is to the influence of coat-thickness.

Table 1, different reduction temperature to thick coating kilsyth basalt 2, reduction soaking time to thick coating

The influence (920 ℃, the Gcr15 mother metal) of influence (being incubated 6 hours, the Gcr15 mother metal) degree

Temperature ℃	The thickness (μ m) of different carbide coatings
						VC	Cr 2C 3	TiC	NbC
950	19	21	25	20
					920	15	18	20	17
860	11	12	16	13

Soaking time (h)	The thickness (μ m) of different carbide coatings
						VC	Cr 3C 3	TiC	NbC
4	8	9	16	11
					6	15	19	20	17
8	18	22	25	19

Can find out from the result of table 1 and table 2, for producing VC, Cr ₃C ₂, NbC and TiC coating adopt 920-950 ℃ temperature and 6 to cause 8 hours hold-time, can reach the coat-thickness that satisfies service requirements.Too high temperature will increase the grain fineness number and the quenching strain of workpiece, and too low temperature or too short soaking time will can not get the carbide coating of desired thickness.

Fig. 2 is given on the Gcr15 steel mother metal, carries out 6 hours insulation under 920 ℃, uses B ₄C reduces V ₂O ₅The VC coating displaing micro picture that (being contained in the flue dust) obtained, Fig. 3 then are on the 40cr steel of base metal through solid carburizing in advance, keep 6 hours at 920 ℃, use B ₄C reduces Cr ₂O ₃The Cr that (being contained in the flue dust) obtained ₃C ₂The coating displaing micro picture.Must be pointed out that 40Cr belongs to medium carbon steel, must could obtain the Cr of Fig. 3 through carburizing in advance 2 hours ₃O ₂Coat-thickness (20 μ m).Experiment points out that the 40Cr steel is not if carburizing in advance directly enters B ₄C reduction coating is handled, same time and temperature, and coat-thickness only reaches 4-5 μ m.A, B, three sections of C are respectively base material, carbide coating and gas cloud in Fig. 2 and Fig. 3.

Fig. 4 and Fig. 5 are respectively elemental vanadium and the electron probe microanalysis result of carbon on the VC of GCr15 steel coating transverse section.As can be seen from Figure 4 and Figure 5, elemental vanadium and carbon are all concentrated and are distributed in the white area band of VC coating, and simultaneously, in the narrow VC coating transitional zone, the concentration of vanadium drops to zero soon, and the concentration of carbon then just drops to the mean concns of mother metal carbon content.These analytical resultss that drawn are consistent coincideing with the formation mechanism of above-mentioned carbide coating, and the VC coating has also been carried out the diffraction facies analysis of X ray, and its result shows that the main phase composite of three kinds of VC coatings all is V ₈C ₇

For three kinds of different VC coating samples are made Electron probe quantitative analysis, process the thickness that grinds off 5 μ m from the sample of each VC coating with grinding machine, then Electron probe quantitative analysis is carried out on the new surface that grinds, the gained result is as shown in table 3.

Table 3: the Electron probe quantitative analysis result of the vanadium carbide coating of different methods preparation

Element	Aluminium reducing	The TD method	B 4The C reduction	V 8C 7Theoretical amount
					C％	22.51	25.67	30.79	17.09
V％	76.13	73.23	67.99	82.9
					C/V	0.29	0.35	0.45	0.206
Free C％	5.42	8.58	13.7	0.0

From the result of table 3 as can be seen, in three kinds of different VC coatings, the size order of free carbon content is: (B ₄C) _{Free C}＞(TD) _{Free C}＞(AL) _{Free C}(1)

The wearing resistance of different coating:

On M200 type wear testing machine, finished the skimming wear drag test of four kinds of different coating, four kinds of tested samples are respectively: by TD method, aluminum reduction method and B ₄Three kinds of VC coating samples that the C reduction method is made and the coating sample of a kind of SCN that in salt bath, prepares ^[9], each tested sample all with identical reference coupon match grinding, reference coupon is a high speed steel W ₆Mo5Cr4V ₂AL, through after quenching back, this rapid steel has the hardness of HRC63-64.Reference coupon is a fixed, tested coating sample then under the load of 180kg with 20 hours (adding the water cooling sample) of 200 rev/mins rotating speed rotation, in examine for wear before and after, tested sample is all weighed analyzing on the Libra.The abrasion detection result of four kinds of various sample as shown in Figure 6, as can be seen from Figure 6, the wear resistance descending order of four kinds of different coating samples is: (B ₄C) _WR＞(TD) _WR＞(AL) _WR＞(SCN) _WR(2)

Relatively behind the inequality (1) and (2), can find: the wear resistance of three kinds of different VC coatings is not only relevant with the free carbon content in the VC coating nearly, but also increases with the rising of the free carbon content in the coating.

The corrosion resistance of VC coating:

VC coating sample and 2Cr13 stainless steel mother metal that three kinds of different methods are prepared all are fixed in the rotating shaft, the hydrochloric acid liquid of putting into 20% concentration stands 15 hours mobile corrosion test, before the corrosion test and after, being verified sample all weighs on the analysis Libra, the test-results of gained as shown in Figure 7, as can be seen from Figure 7, the corrosion resistance of various VC coating is significantly more superior than 2Cr13 Martensite Stainless Steel, simultaneously, the corrosion resistance of three kinds of different VC coatings also is significantly different, and the size order of the corrosion resistance of various VC coating is:

(B ₄C) _CR＞(TD) _CR＞(AL) _CR……(3)

Relatively inequality (1) and (3) it can also be seen that the corrosion resistance of VC coating not only depends on the content of free carbon in the coating, but also increases with the increase of the free carbon content in the coating.

Description of drawings:

The free energy of Fig. 1, oxide compound and the relation of temperature.

B on Fig. 2, the GCr15 steel ₄The VC coating displaing micro picture (X250) that the C reduction is produced.

B on Fig. 3, the 40Cr steel ₄The Cr that the C reduction is produced ₃C ₂Coating displaing micro picture (X250, carburizing in advance).

Fig. 4, B ₄Elemental vanadium distribution (X1000, GCr15 steel mother metal, VK α electronic probe face scintigram) on the VC coating transverse section that the C reduction is produced.

Fig. 5, B ₄Elemental carbon distribution (X1000, GCr15 steel mother metal, CK α electronic probe face scintigram) on the VC coating transverse section that the C reduction is produced.

Fig. 6, four kinds of different coating (B ₄C reduction VC coating, TD method VC coating, AL reduction VC coating, SCN co-osmosized coating) skimming wear speed.

Fig. 7, four kinds of differing materials (B ₄C reduction VC coating, TD method VC coating, AL reduction VC coating and 2Cr13 stainless steel) mobile corrosion speed in 20% hydrochloric acid soln.

Embodiment:

Embodiment 1:

Cigarette tongue (pressure glossal canal) in the import high-speed cigarette machine of 12000 of per minute product cigarettes is gone up preparation vanadium carbide hard-surface coating.

The composition Na of blank salt bath ₂B ₄O ₇: NaF=85%: 15% (weight).After blank salt bath becomes fractional melting, add B ₄C powder and contain V ₂O ₅Be ferroalloy works' flue dust of 86.4%, V ₂O ₅Add-on be blank salt bath heavy 10%, and contain V ₂O ₅The dosage of flue dust be blank salt bath heavy 11.58%, B ₄The add-on of C is V ₂O ₅Heavy by 17%, B ₄C with contain V ₂O ₅The flue dust powder mixes after add in the molten salt bath and stir, and be warmed up to 920 ℃ of insulations.After adding salt bath through 2 hours 40Cr steel cigarette tongue mother metal of ordinary method carburizing in advance, be incubated after 6 hours, adjust the austenite transformation temperature (850 ℃) of salt temperature to the 40Cr steel, and the cigarette tongue was taken out in insulation in 10 minutes then under one temperature of back, quench immediately under the condition of high temperature and cool off in the machine oil, change over to boil in the ebullient soda water after cooling finishes and boil 5 minutes, to remove the residual salt that adheres on the workpiece, boil the cigarette tongue of finishing, change in the box-type furnace, 180 ℃ of following tempering two hours, take out behind the furnace cooling then, thickness is that the preparation procedure of the VC coating of 15 μ m all finishes, and its matrix hardness reaches HRC63～64, and coating hardness reaches HV2900～3200.This cigarette tongue is installed on Britain or the German import high-speed cigarette machine and uses, and its non-stop run life-span reaches 140～150 days, and the working life of this cigarette tongue is higher than the cigarette tongue of Britain or German import, but its price only be Britain or German import the cigarette tongue 18%.

Embodiment 2:

Cigarette (stalk) the silk cutter (cutter of cutting cigarette bone) of cutting in the tobacco leaf cutting of production of cigarettes factory is gone up preparation titanium carbide hard-surface coating.

The composition Na of blank salt bath ₂B ₄O ₇: NaF=85%: 15% (weight).After blank salt bath composition melts, add the B that mixes in the stainless steel crucible ₄C powder and contain TiO ₂Flue dust, TiO wherein ₂Add-on be that 10% of blank salt bath (is converted into and contains TiO ₂84.7% flue dust is 11.81%), B ₄The add-on of C is TiO ₂20.7% of dosage stirs salt bath then, and insulation after being warmed up to 950 ℃, waits for the adding of blade.By high speed steel W ₆Mo5Cr4V ₂AL is preheating in box-type furnace after 600 ℃ as cigarette (stalk) the silk blade of cutting of mother metal, changes over to fast in the ready above-mentioned salt bath, and blade hangs in the salt bath, and the preparation process of coating was finished in insulation in 6 hours under 950 ℃ temperature.After this, again blade is transferred in the electric pole type heating High Temperature Salt Bath Furnace that is heated to 1220 ℃, and under 1220 ℃, be incubated 5 minutes, so that allowing the rapid steel mother metal finish austenite transforms, then blade is taken out from high-temperature salt furnace, in the biplate of the quenching cooling punching block, absorb the purpose that the blade heat reaches chilling by plump punching block, because the length and width size of blade is bigger more than 100 to 200 times than thickness, such sheet-like workpieces cools off in oil or in the water and is easy to produce big distortion, and cool off in the biplate cooling punching block of quenching, the be cooled big weight of upper and lower mould of quenching strain is corrected, mould is cold finish after, blade takes out to enter and boils in the soda boiling water eliminating the salt residue on the blade, then quench in entry cooling and dry up and treat to use next time of punching block.After boiling end, blade changes over to and keeps in the box-type furnace carrying out tempering in two hours under 560 ℃ temperature, and tempering need repeat twice.Through the blade after coating like this and the thermal treatment, matrix hardness reaches HRC63～64, and coating hardness reaches HV2900～3200, and the TiC coat-thickness reaches 20 μ m.This blade input is cut in the production of tobacco leaf and is used, and its non-stop run life-span reached about 70～75 hours, improve more than 1 times than the import tobacco cutter, but price only is about 25% of import cutting knife.

Embodiment 3:

The Cr of the cold-heading drawing of producing at standardized component (screw and nut) ₁₂Preparation chromium carbide hard surface coating on the MoV upper punch.

The composition Na of blank salt bath ₂B ₄O ₇: NaF=85%: 15% (weight).After blank salt bath composition melts in the stainless steel crucible, Cr ₂O ₃Add-on be 10% (dosage that is converted into flue dust is 11.74%) of blank salt weight, B ₄The add-on of C is Cr ₂O ₃16.6% of dosage, B ₄Add the blank salt bath that has melted behind C powder and the flue dust mixing, after stirring, be warmed up to the adding of 935 ℃ of wait drifts.Finish after the machining and be preheating to 600 ℃ Cr ₁₂The MoV upper punch joins in the above-mentioned molten salt bath, and keeps 6 hours down at 935 ℃, is warmed up to 960 ℃ then and keeps 10 minutes, transforms so that the drift base material is finished austenite, after this drift is quenched and is cooled off in the machine oil, enters after cold to contain Na ₂CO ₃Boiling water in boil and remove residual salt, then 180 ℃ of following tempering two hours.This moment, the hardness of drift base material reached about HRC58, and the hardness of coating is HV1600～1800, Cr ₃C ₂The thickness of coating is 19 μ m.Cr ₃C ₂The non-stop run life-span of coating upper punch is brought up to and can produce 40,000 nuts, improves 5 times than the upper punch of handling without coating.

Embodiment 4:

The Cr of cold-heading drawing in standardized component (screw and nut) is produced ₁₂Preparation niobium carbide hard-surface coating on the MoV lower punch.

The composition Na of blank salt bath ₂B ₄O ₇: NaF=85%: 15% (weight).Nb ₂O ₅By heavy 10% the adding of blank salt bath, be converted into and contain Nb ₂O ₅82.9% iron closes factory's flue dust, then the add-on of flue dust be blank salt bath heavy 12.1%, B ₄The add-on of C powder is Nb ₂O ₅15.5% of dosage.After blank salt bath melts in the stainless steel crucible, containing Nb ₂O ₅Flue dust and B ₄After the C powder mixes, add in the molten salt bath, and stir.Then, salt temperature is raised to 950 ℃, waits for that workpiece adds.And machining is finished, and through the Cr of preheating under 600 ℃ the temperature ₁₂The MoV lower punch, be added in the above-mentioned salt bath after, 950 ℃ of down insulations 8 hours, adjust salt temperature to 960 then and ℃ kept 10 minutes transform so that finish austenite, after this, drift is taken out, cool off in the machine oil of quenching, enter after cold and contain Na ₂CO ₃Boil in the boiling water and remove salt residue, then 180 ℃ of following tempering two hours.Through the lower punch of above-mentioned processing, the thickness of NbC coating reaches 20 μ m, and base material hardness reaches HRC58, and the NbC coating hardness reaches HV2600～2800.Through the M12 nut lower punch of above-mentioned NbC coating, a product surplus its non-stop run life-span Danone produces 36000 improves 5.5 times than the lower punch of handling without coating.

Claims (2)

1, a kind of method for preparing metal carbonide hard face coating is characterized in that using technical pure B in the molten salt bath of being made up of 85% heavy industrial borax and 15% industrial Sodium Fluoride heavily ₄The C powder, reduction contains ferroalloy works' flue dust of 83-87% metal oxide respectively, and the metal oxide in the flue dust is V ₂O ₅Or Cr ₂O ₃Or TiO ₂Or Nb ₂O ₅, in salt bath on the heated iron and steel mother metal, obtain hardness and reach HV1600～3200, thickness be 15-22 μ m contain VC or Cr ₃C ₂Or the hard-surface coating of TiC or NbC; Wherein:

1.1, the reductive agent that forms carbide coating is technical pure B ₄The C powder, B ₄The C powder size is less than 60 orders;

1.2, the processing condition of metal-carbide coating are; Workpiece is heated to temperature 920-950 ℃, be incubated after 6-8 hour, then the temperature of salt bath is adjusted to steel of base metal is quenched under the necessary austenite transformation temperature, look workpiece and vary in size, kept 5 to 15 minutes, then workpiece is taken out from salt bath and the oil of quenching in, treat that workpiece cools off in oil after, put into boiling water and boil, remove the salt bath residue on the workpiece, then, again workpiece is put into the box-type furnace tempering; If steel of base metal is a carbon content less than in 0.9% or soft steel, then steel of base metal needs through carburizing in advance, to guarantee to form the required carbon content of carbide;

1.3, B ₄C powder and oxidiferous flue dust constitute the active additive of preparation metal-carbide coating, the add-on that forms the required active additive of metal-carbide coating is: the add-on of metal oxide be the borax fusion salt bath heavy 10%, the content of metal oxide in the add-on of flue dust=10% salt bath weight/flue dust; B ₄The C add-on is difference with the difference of producing the carbide coating kind, when the coating of producing is respectively VC, Cr ₃C ₂, when NbC and TiC, B ₄The add-on of C is respectively 17.0%, 16.6%, 15.5% and 20.7%.

2, method according to claim 1 is characterized in that the hard-surface coating of this hard-surface coating as resistance to abrasion and demanding workpiece of erosion resistance or member.

Images