CN1031950C - Salt bath process for rare-earth-vanadium-boron co-diffusion - Google Patents
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Abstract
The present invention relates to a rare earth vanadoboriding technique. A fusion salt bath is used as a carrier; appropriate rare earth is added in the salt bath for co-penetration for four hours at 950 DEG C more or less. The penetration layer of the technique is thicker than the vanadizing and vanadoboriding layers, and the microhardness is higher than the hardness of a single boronising layer and a vanadoboriding layer. A rare earth vanadoboriding layer has the advantages of high hardness and compact structure and overcomes the defect of loose boride existing in a single boronising surface layer; the single boronising boron brittleness is effectively inhibited; the structure form is improved; the abrasion resistance of the penetration layer is improved, and the penetration layer has favorable comprehensive mechanical performance. Therefore, the technique centralizes the advantages of a single vanadizing technique and a single boronising technique and obtains perfect effect.
Description
The present invention relates to a kind of salt bath process for rare-earth-vanadium-boron co-diffusion.
Current application surface engineering is to improve the Technology of die life, be subjected to people's generally attention and research just day by day, wherein boronising and vanadinizing technology successfully are applied to obtain effect preferably on wearing piece and the tool and mould through the systematic study of two more than ten years.Though single boronising can obtain thicker infiltration layer, fragility is big, easily peels off, and compactness is poor.Though and single vanadinizing can obtain the infiltration layer of high rigidity, infiltration layer is thin, can not bear the service requirements of heavier load, thereby limit its range of application greatly.
The object of the present invention is to provide this technology of a kind of salt bath process for rare-earth-vanadium-boron co-diffusion that high rigidity, high abrasion, low brittle co-penetration layer tissue can be provided, to satisfy the requirement of the mould service condition that bears big load, enlarge the range of application of mould, the work-ing life of improving mould greatly.
The object of the invention is achieved through the following technical solutions:
One, salt bath rare-earth-vanadium-boron co-diffusion theoretical foundation:
As salt bath, the borax fusing point is 740 ℃ with borax, will be decomposed into sodium metaborate and boron trioxide after the fusion:
According to the free energy (Δ F) of boron, vanadium and aluminium generation oxide compound, as shown in Figure 1, as can be known, in 800-1200 ℃ of scopes, boron is defeated by vanadium, aluminium and is defeated by boron again, shown in aluminum ratio boron and vanadium all be easy to form oxide compound, and boron is than the easy formation oxide compound of vanadium, in vitrified borax is bathed, when adding V
2O
5Behind the AL powder, aluminium has abundant chance to meet B
2O
3And V
2O
5, as aluminium while and V
2O
5And B
2O
3When meeting, because the cause of thermodynamic condition, aluminium will at first displace vanadium, if aluminium elder generation and B
2O
3Meet, press thermodynamic condition, will displace element boron equally, but owing in the fused salt V is arranged
2O
5Exist, so boron is under sufficient dynamic conditions, the most at last with V
2O
5The effect and displace vanadium, work as V
2O
5After all effect finished, unnecessary aluminium just began to displace B
2O
3In boron, and under in fused salt, keeping.
Can calculate by chemical equation (1), work as V
2O
5With the weight ratio of AL be 1: 0.5 o'clock, V
2O
5All replaced, so in the borax salt bath, add V
2O
5With the weight ratio of AL be 1: 0.5 o'clock, when the carbon steel work-piece in the salt bath changes austenite on transformation temperature, strong carbide forming element vanadium just to part from table and in spread, in the basic material carbon to surface transport, thereby obtain the vanadium carbide coating at workpiece surface.When adding excessive reductant AL, i.e. V
2O
5With the weight ratio of AL greater than 1: 0.5 o'clock, the AL in the salt bath is with V
2O
5Vanadium all replace, so Yu Xia AL just displaces the B atom by formula (2), so workpiece surface begins boronising, just can realize vanadium-boron co-diffusion [Li Zhujun etc., Jinzhou Polytechnic College's journal, 1988 (4), 8-14; Liu Junli etc., boronising and metallic cementation in the borax fused salt, " thermal treatment association of Chinese Mechanical Engineering Society is nd Annual Meeting for the second time " 1979,2].
Because rare earth element has the 4f shell structure, its chemically reactive is big, with the avidity of oxygen stronger [I Barin and O Knacke " Thermochemicalprropcrties of inorgnic substances " New York.1973 than aluminium, 217] temperature is decomposed, thereby in fused salt active rare earth atom and V
2O
5And B
2O
3Carry out reduction reaction, thereby increase the reaction of penetration enhancer, produce more active vanadium atom and active boron atom, the active vanadium atom and the active boron atomic percent that are adsorbed on the steel surface are improved, cause vanadium atom and boron atomic percent gradient u/ x increase in the infiltration layer, vanadium atom and boron atom flux J=-D u/ x that surface diffusion is infiltrated increase [Chen Chongwei etc., rare earth, 1990 (3), 16-21], quickened the generation of vanadium-boron penetrating layer.
B
2O
3+ 2RE RE
2O
3+ 2[B] on the other hand,, in diffusion process, cause the additional distortion of lattice because the large scale rare-earth atom at first infiltrates, be beneficial to the transition [Peng Risheng etc. of carbon atom, heat processing technique 1991 (1), 13-16], in addition, the infiltration of rare earth atom produces vacancy atoms group around it, room and dislocation desity are increased, for vanadium atom and boron atomic diffusion provide more by all kinds of means [Wang Shiqing etc., metal heat treatmet, 1988 (3), 52-59].So in vanadium-boron co-diffusion, add an amount of rare earth, can play and urge effect of oozing and microalloying, thereby realize the salt bath rare-earth-vanadium-boron co-diffusion.
Fig. 1 is oxide compound standard free energy of formation Δ F and temperature relation curve.
Fig. 2 is salt bath composition proportion alloying layer thickness and a microhardness relation curve together.
Fig. 3 is for adding the resulting co-penetration layer metallographic structures of different rare earth contents (a～e five width of cloth figure).
Fig. 4 is alloying layer thickness, hardness and rare earth addition relation curve.
Fig. 5 is a co-penetration layer cross section Hardness Distribution curve.
Table 1 is for oozing the influence of temperature to alloying layer thickness and microhardness altogether.
Table 2 is for oozing the influence of time to alloying layer thickness and microhardness altogether.
Table 3 is different matrix steel co-penetration layer thickness, tissue morphology and a microhardness.
Table 4 is reused number of times and alloying layer thickness for salt bath.
Two, the concrete technology of salt bath rare-earth-vanadium-boron co-diffusion
1, salt bath composition proportion:
As salt bath, adding proportion is 1: 1～1: 1.6 V in salt bath with vitrified borax
2O
5: AL.
Work as V
2O
5: AL is 1: 1.3 o'clock, and it is fine and close continuously to obtain diffusion layer organization, and infiltration layer is also thicker, and microhardness value is also higher, and salt bath is better mobile.And work as V
2O
5: AL was less than 1: 1 o'clock, and the infiltration layer of acquisition mainly is the vanadinizing layer, and infiltration layer is thin.And work as V
2O
5: AL was greater than 1: 1.6 o'clock, and obtaining infiltration layer mainly is to ooze the B layer, though infiltration layer is thick, organize densification inadequately, and salt bath was mobile poor.Its result is (experiment condition is: material C r12MoV950 ℃ * 4 hV-B oozes altogether, and wherein I is that alloying layer thickness, II are microhardness) as shown in Figure 2.
2, the rare earth addition influences the co-penetration layer structure property:
The rare earth addition is advisable with 4～6% (salt bath total amounts).
Fig. 3 organizes metallograph for the rare earth addition from zero co-penetration layer that increases progressively successively.From these photographs, can observe, adding an amount of rare earth (4～6% salt bath total amount) obtains co-penetration layer thickness (60～75 μ m) and comes thickly than the co-penetration layer thickness that does not add rare earth (40～55 μ m), and layer surface hardness also increases, see Fig. 4 (processing condition: material C r12MoV950 ℃ * 4h RE-V-B oozes altogether, and wherein I is that alloying layer thickness, II are microhardness).
The micro-hardness testing result shows along the co-penetration layer cross section, add an amount of rare earth, make co-penetration layer come gently than the co-penetration layer that does not add rare earth along the cross section hardness gradient, be that the Hardness Distribution condition curve is more satisfactory, see that (processing condition: material C r12MoV950 ℃ * 4hRE-V-B oozes Fig. 5 altogether, wherein I is for adding an amount of RE, and II is not for adding RE).
3, ooze temperature, time altogether to co-penetration layer tissue, performance impact.
Oozing temperature altogether and be advisable with 920 ℃～1000 ℃, is the best with about 950 ℃ wherein.The time of oozing altogether is more suitable with about 4 hours.
Along with the variation of oozing temperature and time altogether, the thickness of co-penetration layer and hardness are also corresponding to change.Table 1 is under differing temps, and Cr12MoV steel sample oozes the situation of resultant infiltration layer after 4 hours altogether.By table 1 as seen, with the raising of oozing temperature altogether, co-penetration layer thickness increases.Metallographic structure is observed and is shown that also with the raising of oozing temperature altogether, the broach of infiltration layer front end shortens gradually, and the island structure of zone of transition obviously reduces, even disappears.The infiltration layer microhardness also rises to some extent with the raising of oozing temperature altogether, but this trend is being slowed down more than 950 ℃.
It is as shown in table 2 to diffusion layer organization, Effect on Performance that the Cr12MoV steel oozes the time altogether.With oozing time lengthening altogether, alloying layer thickness increases, but its tissue morphology and microhardness change not quite.From practical application consider RE-V-B altogether the time of oozing get 4 hours just enough.
From last visible employing method of the present invention, in salt bath, add an amount of rare earth, can play and significantly urge the effect of oozing, can improve infiltration rate about 30%, alloying layer thickness significantly increases under the condition oozing equally altogether, improves the diffusion layer organization form simultaneously, makes infiltration layer fine and close more, thereby the raising nitrided layer hardness, and improve infiltration layer cross section Hardness Distribution state.
Three, salt bath rare-earth-vanadium-boron co-diffusion layer thickness and The performance test results:
1, co-penetration layer thickness and microhardness: 950 ℃ * 4h of Cr12MoV steel salt bath list oozes V, singly oozes that B, V-B ooze altogether and RE-V-B co-penetration layer thickness and micro-hardness testing result such as table 3.
Test-results shows that under the same process condition, RE-V-B co-penetration layer thickness is much thicker than the thickness that singly oozes V, about the also thick 20 μ m of infiltration layer that ooze altogether than V-B, but than singly oozing the thin of B.RE-V-B co-penetration layer microhardness will be higher than the microhardness of singly oozing B and V-B co-penetration layer, singly oozes V but be lower than.From the diffusion layer organization density, the top layer of RE-V-B co-penetration layer is VC, and sublevel is (FeCr)
2B, Fe
2B has the compact structure of high rigidity, overcome to have avoided singly oozing the tissue that there is loose boride in the B upper layer, thereby the boron that has also suppressed singly to ooze B effectively crisp, improved tissue, improved the comprehensive mechanical performance of infiltration layer.Therefore, RE-V-B oozes and can concentrate the advantage of singly oozing V and singly oozing two kinds of technologies of B, obtains the effect of maximizing favourable factors and minimizing unfavourable ones.
2, co-penetration layer fragility comparative test result:
950 ℃ * 4h of Cr12MoV steel is oozed singly that B, v-B ooze altogether and RE-V-B oozes sample altogether and adopts the Vickers' hardness pressing in method, contrasted the fragility of three kinds of surperficial cementation process infiltration layers, test result such as table 4.
Test-results shows, RE-V-B oozes altogether or V-B oozes altogether and improved infiltration layer fragility significantly, that is to say, the boron that polynary boronising can suppress singly to ooze B effectively is crisp, and this result with document announcement is consistent, and [Russia and the U.S. holds etc., metal heat treatmet, 1991 (4), 26-31].
RE-V-brittle improvement of B co-penetration layer is because mainly there is fine and close VC and (FeCr) in the co-penetration layer top layer
2B, Fe
2B tissue, FeB is few for the fragility phase, and VC distributes with the particulate disperse state again on the co-penetration layer top layer, and this all plays useful effect to reducing infiltration layer fragility.
(3), co-penetration layer wear resistance comparative test result
The Cr12MoV steel is singly oozed B through 950 ℃ * 4h, and V-B oozes altogether and RE-V-B oozes altogether and handles back three kinds of surperficial cementation process samples and carry out wear resistance simultaneous test, result such as table 5, table 6.
Experimental result shows, RE-V-B oozes the sample wear resistance altogether and is higher than and singly oozes B and V-B oozes sample altogether.RE-V-B oozes wear resistance altogether and is about 2.4 times that singly ooze the B wear resistance, oozes 1.2 times of wear resistance altogether for V-B.
Why RE-V-B has higher wear resistance than boronising if oozing altogether, mainly be that VC is distributed in the infiltration layer top layer with superfine little granular form disperse like this owing to formed the carbide of the higher vanadium of hardness ratio FeB on the top layer of co-penetration layer.Secondly, the densification of co-penetration layer textura epidermoidea does not have the boronising top layer to be easy to occur tectorium, and decision has all played to the raising of wear resistance in these organizational factors of co-penetration layer.
Embodiment one
Carbon content and alloying element are to co-penetration layer tissue, performance impact.
Cr12MoV, Cr12,9CrSi, T
8Four kinds of steel capital are high carbon tool steels, and wherein Cr12MoV and Cr12 belong to the high-carbon high-alloy tool steel, and 9CrSi belongs to high-carbon low-alloy tool steel, T
8Belong to high carbon tool steel, these four kinds of steel are Cr12, Cr12MoV, 9CrSi, T by carbon content height order
8Steel is Cr12MoV by alloying element content height series arrangement.
Cr12,9CrSi, T
8(alloy-free element) steel.It the results are shown in Table 7.
Under 950 ℃ * 4h RE-V-B confusion technology condition same case, obtain co-penetration layer thickness, tissue morphology and microhardness are along with carbon in the steel matrix is different and different with alloying element content.Show relative low 9CrSi of carbon and T with alloying element content through metallographicobservation
8Steel, co-penetration layer are thicker relatively, and tissue is significantly broach shape.And the Cr12MoV of high-carbon high-alloy is relative thinner with Cr12 steel co-penetration layer, and does not have tangible broach shape, and the zone of transition island structure increases.But four kinds of steel ooze rear surface microhardness (HV altogether
0.1) difference is little.
Because dissolved carbon not in the boronising, thereby with the increase of matrix carbon content, boride layer thickness descends, and is unfavorable for boronising.But for vanadinizing, the carbon amount is higher, and the active atoms of carbon diffusion flux is also bigger in the matrix, forms the VC coating easily, helps vanadinizing.So the matrix carbon content is concerning RE-V-B oozes altogether, the two is to be among the contradiction of the unity of opposites.
The matrix alloy element the more, the obstacle that will get rid of when forming boride layer the more is unfavorable for boronising.But the diffusion flow ununiformity increases, and forms the hole and increases, and this is favourable to vanadinizing.Then to capture a part of carbon and form stable carbide if alloying element is strong carbide forming element such as W, Cr, Mo, V.This is unfavorable for vanadinizing [Zhang Suying etc., metal heat treatmet, 1986 (5), 29-34]; The two is taken all factors into consideration, alloying element the more, it is disadvantageous that RE-V-B is oozed altogether.
In sum, salt bath RE-V-B confusion technology is to a large amount of Cr12MoV, Cr12,9CrSi, GCr15, CrWMn, T commonly used
10, T
8Cold-work die steel can both obtain satisfied co-penetration layer tissue and performance.
Embodiment two
Salt bath is reused number of times to the co-penetration layer thickness effect
Cr12MoV steel sample is in same pincers crucible salt bath, in 950 ℃ * 4h rare-earth-vanadium-boron co-diffusion, reuse seven heats continuously, each alloying layer thickness of measuring changes, the results are shown in Table 8, co-diffused salt bath is not adding under any new dose situation, can use continuously 4～5 times, and alloying layer thickness can also keep 40～50um, when using the 6th, the 7th time, because non-stop run, the workpiece surface of at every turn coming out of the stove is taken out of and is adhered to the salt bath loss, and active V, the oxidized stable oxide that becomes of B atom in the salt bath, cause the salt bath activity to decay gradually, so slowly attenuation of alloying layer thickness.At this moment, after adding once a small amount of new salt and add that 1～2%AL powder adds 0.5% rare earth (accounting for the salt bath total amount) again and recovered the salt bath activity by former proportioning, reuse continuously again five times.Measure each alloying layer thickness and change recovery as before.Co-diffused salt bath stability is described better, can reuse 4～5 times continuously after, add once a small amount of new agent and activated, can use continuously again.
Table 1 oozes the influence of temperature to alloying layer thickness and microhardness altogether
Annotate: the sample hardness value is at least 3 mean values.Table 2 oozes the time altogether to alloying layer thickness and microhardness influence
| Ooze altogether temperature (℃) | Ooze the time (h) altogether | Alloying layer thickness (μ m) | Microhardness (HV 0.1) |
| 850 | 4 | 20—25 | 2031 |
| 900 | 4 | 25—30 | 2091 |
| 950 | 4 | 61—77 | 2195 |
| 1000 | 1 | 62—74 | 2138 |
| Ooze altogether temperature (℃) | Ooze the time (h) altogether | Alloying layer thickness (μ m) | Microhardness (HV 0.1) |
| 950 | 2 | 37—13 | 2136 |
| 950 | 4 | 61—77 | 2195 |
| 950 | 6 | 62—74 | 2183 |
| 950 | 8 | 62—79 | 2190 |
Four kinds of surperficial cementation process alloying layer thicknesses of table 3 and microhardness contrast
| The surface cementation process | Alloying layer thickness (μ m) | Microhardness (HV 0.1) | Remarks |
| Singly ooze V | 7—9 | 2400—2800 | Microhardness value is data [9] data |
| | 100 | 1500—1800 | ″ |
| V-B oozes altogether | 45 | 1854—1892 | Experimental data |
| RE-V-B oozes altogether | 65 | 1931—2195 | ″ |
Three kinds of surperficial cementation process infiltration layer fragility contrasts of table 4
| The surface cementation process | The impression state |
| Singly ooze B | Impression is cracked on one side, and impression sharp corner crack length is longer. |
| V-B oozes altogether | Impression does not occur cracked, and impression sharp corner crack length is shorter. |
| RE-V-B oozes altogether | Impression does not occur cracked, and impression sharp corner crack length is shorter. |
Table 8 salt bath is reused number of times and alloying layer thickness
| Access times |
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | |
| Alloying layer thickness (μ m) | 70～ 73 | 68～ 72 | 60～ 67 | 40～ 55 | 35～ 38 | 25～ 30 | 12～ 20 |
Table 5 oozes singly that B, V, B ooze altogether and RE-V-B oozes abrasion loss (g) altogether
| Treatment process | Wearing-in | ||||
| 1 | 2 | 3 | 4 | 5 | |
| Singly ooze the B+ Q-tempering | 0.0032 | 0.0064 | 0.0092 | 0.0123 | 0.0165 |
| V-B oozes+Q-tempering altogether | 0.0027 | 0.0047 | 0.0060 | 0.0070 | 0.0083 |
| RE-V-B oozes+Q-tempering altogether | 0.0020 | 0.0040 | 0.0048 | 0.0057 | 0.0068 |
Table 6 oozes singly that B, V-B ooze altogether and RE-V-B oozes relative wear resistance relatively altogether
Relative wear resistance
| Singly ooze B | V-B oozes altogether | RE-V-B oozes altogether |
| 1 | 1.99 | 2.43 |
Table 7 different matrix steel co-penetration layer thickness, tissue morphology and microhardness
| Steel grade | 950 ℃ * ooze altogether with h RE-V-B | ||
| Alloying layer thickness (μ m) | Tissue morphology | Microhardness (HV 0.1) | |
| | 60—75 | There is not obvious broach shape | 1971—2195 |
| Cr12 | 60—80 | There is not obvious broach shape | 1930—1970 |
| 9CrSi | 85—95 | Obviously broach shape is arranged | 1990—2032 |
| | 60—85 | Obviously broach shape is arranged | 1970—2054 |
Claims (1)
1, a kind of is the salt bath process for rare-earth-vanadium-boron co-diffusion of carrier with the vitrified borax, it is characterized in that: add V in salt bath
2O
5With AL powder, V
2O
5With the proportioning of AL powder be 1: 1～1: 1.6, in this salt bath, add the rare earth of 4～6% (accounting for the salt bath total amount) again; Oozing temperature altogether is between 920～1000 ℃, and the time of oozing got 4 hours altogether.
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|---|---|---|---|
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| CN101914749A (en) * | 2010-07-20 | 2010-12-15 | 阎逸飞 | New salt bath vanadatizing method and new salt bath vanadatizing agent |
| HUE051721T2 (en) * | 2013-02-06 | 2021-03-29 | Arcelormittal | Method of treatment of a running ferrous alloy sheet and treatment line for its implementation |
| CN103436893A (en) * | 2013-08-14 | 2013-12-11 | 徐州工程学院 | Rare earth boronizing process for roller |
| CN103589991B (en) * | 2013-10-25 | 2016-06-01 | 沈阳建筑大学 | The rare earth of a kind of stainless steel cold punching die oozes vanadium method |
| CN103692635A (en) * | 2013-12-18 | 2014-04-02 | 章鹏 | High-wear-resistance iron boride alloy screw element for double-screw machine, and manufacturing method of iron boride alloy screw element |
| CN104195573A (en) * | 2014-09-11 | 2014-12-10 | 东莞诚兴五金制品有限公司 | Surface treatment process of mould |
| CN105239037A (en) * | 2015-11-02 | 2016-01-13 | 杭州持正科技股份有限公司 | Chain pin shaft surface vanadinizing strengthening process |
| CN110218968B (en) * | 2019-06-21 | 2020-01-31 | 牡丹江师范学院 | Method for improving corrosion resistance of steel surface by low-temperature liquid-phase diffusion |
| CN113073290B (en) * | 2021-03-26 | 2021-11-02 | 长沙特耐金属材料科技有限公司 | Preparation method of metal-based material coated with multi-component composite coating |
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