CN100587118C - Method for directly growing nano-crystal chromium nitride film on steel products - Google Patents

Method for directly growing nano-crystal chromium nitride film on steel products Download PDF

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CN100587118C
CN100587118C CN200710031163A CN200710031163A CN100587118C CN 100587118 C CN100587118 C CN 100587118C CN 200710031163 A CN200710031163 A CN 200710031163A CN 200710031163 A CN200710031163 A CN 200710031163A CN 100587118 C CN100587118 C CN 100587118C
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salt
powder
salt bath
basic salt
steel
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CN101148769A (en
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曹辉亮
伍翠兰
刘江文
邹敢锋
罗承萍
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South China University of Technology SCUT
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Abstract

The process of growing nanometer crystalline chromium nitride film directly on steel includes the first nitriding and the salt bath chromizing of the nitrided steel at 500-650 deg.c after being cooledto room temperature and surface washing. The salt bath fluid for salt bath chromizing has base salt comprising NaC l20-25 wt%,BaCl2 30-35 wt% and CaCl2 40-50 wt%; and effective components including Cr powder 10-20 wt% of the base salt, Fe powder 5-10 wt% of the base salt, CrCl3.6H2O 25-50 wt% of the base salt, and Si powder 5-10 wt% of the base salt. The process grows nanometer crystalline CrN film directly on steel, and the film has great base bonding force, effect of reducing friction, fast growing speed and high suitability of steel types.

Description

A kind of directly method of growing nano-crystal chromium nitride film on steel
Technical field:
The present invention relates to a kind of material surface treatment method, particularly a kind of steel surface method for making Nano, the i.e. direct method of growing nano-crystal chromium nitride film on steel.
Background technology:
Because most of inefficacy the (for example, fatigue, corrosion, wearing and tearing etc.) all occurs in the surface of material, so material surface modifying is subjected to investigators' extensive attention always.Nanostructured surface is owing to have good stretching, and antifatigue wear-resistantly undermines the focus that the corrosive performance is studied especially.Difference according to the nano material synthesis mechanism, the current material method for making Nano surface can be divided into three major types: the first kind is based on the nanometer of various top coats or deposition technique realization, physical/chemical gas deposition (PVD/CVD) for example, and plating etc., the key of these class methods is, guarantee between nanometer layer and the matrix, and the mortise between the nano particle in the nanometer layer; Second class methods are surface self nanometer of realizing under the constant situation of material surface chemical ingredients keeping, these class methods comprise steel brush technology sandblast technology, making Nano surface reinforcing process (SNH), impact technology, blasting technology, and surface mechanical attrition technology; The 3rd class is that hybrid mode combines the making Nano surface technology with chemical treatment, when the nanostructure top layer forms or after forming, material is carried out chemical treatment, top layer at material forms sosoloid or the compound different with the matrix composition, owing to produced a large amount of crystal boundaries in the making Nano surface process, this just provides the ideal passage for atomic diffusion, thereby promotes chemical treatment to carry out.
On the other hand, chromium nitride (CrN) is because its excellent physics and mechanical property also are subjected to extensive concern in recent years.The nowadays more common method for preparing chromium nitride film that can be used in, mainly be physical/chemical gas deposition (PVD/CVD), chemical vapor deposition often needs high processing temperature (700～1200 ℃), under high like this treatment temp, the matrix of processed workpiece is thick, and distortion is serious, though physical vapor deposition methods can be carried out under 200～500 ℃, but Elements Diffusion is few between film that this method obtains and matrix, thereby bonding force is not good.In recent years, a kind of compound thermal response deposition/diffusion (TRD) technology has received some investigators' concern, and this technology tentatively demonstrates the reduction treatment temp, reduces the advantage of workpiece deformation.But the TRD technology common characteristic of bibliographical information is exactly that speed of response is fast inadequately, obtain valuable chromium nitride layer, often needs to grow the treatment time of (tens hours).Bibliographical information is arranged, and 570 ℃ need be carried out the TRD processing just obtains 8 μ m after 50 hours chromium nitride down in fluidized-bed.Secondly, existing TRD technical finesse temperature is higher, and the visible minimum temperature of document is reported as 570 ℃.Under such treatment temp, if film growth rates is fast inadequately, processed workpiece still has the danger of distortion, thereby suitable steel grade is less; At the present situation of TRD technology, the author sets up and has developed a kind of new TRD treatment technology, and this technology has improved the speed of response of TRD greatly, shortened the treatment time, reduced treatment temp, and can be on steel direct growth nano silicon nitride chromium thin film, thereby have prospects for commercial application.In addition, though it is a lot of to have the method for preparing nano material now, most of method and technology complexity only rests on the laboratory study stage, and there is certain difficulty in industrialized mass production.The material surface method for making Nano so people begin one's study, but so far, directly the steel surface method for making Nano of growing nano-crystal chromium nitride film does not appear in the newspapers as yet on steel.Material surface nanometer research thinking has been enriched in the proposition of this method for making Nano surface.
Summary of the invention:
The objective of the invention is to overcome the shortcoming of prior art, provide a kind of scope of suitable steel grade big, control condition is simple relatively, the direct method of growing nano-crystal chromium nitride film on steel in large-temperature range.
Purpose of the present invention is achieved through the following technical solutions:
A kind of directly on steel the method for growing nano-crystal chromium nitride film comprise the steps:
(1) nitriding is handled, and steel is carried out nitriding handle after just handling;
(2) salt bath chromizing is handled, and the steel after step (1) is handled carry out 500 ℃～650 ℃ following salt bath chromizings again and handle after being chilled to room temperature and doing the surface and cleaning; Salt bath is made up of basic salt and effective constituent; By percentage to the quality, wherein basic salt is by NaCl20～25%, BaCl 230～35% and CaCl 240～50% form; In basic salt mass percent, effective constituent is: 200 order Cr powder 10～20%, Fe powder 5～10%, CrCl 36H 2O 25～50% and Si powder 5～10%;
Or salt bath chromizing be treated to steel after step (1) is handled be chilled to room temperature and do the surface clean after, under 580～650 ℃ of treatment temps, carry out chromising again and handle, salt bath is made up of basic salt and effective constituent; By percentage to the quality, wherein said basic salt is by CaCl 246～50%, NaCl 46～50% and KCl 0～8% form; In basic salt mass percent, effective constituent is: 200 order Cr powder 10～20%, Fe powder 5～10%, CrCl 36H 2O 25～50% and Si powder 5～10%.
For further realizing the object of the invention, described nitriding is treated to ionitriding or gas nitriding.
It is to carry out nitriding to handle under 540～650 ℃ of treatment temps that described nitriding is handled.
Described salt bath chromizing treatment process: the basic salt fusing that will mix in crucible furnace earlier adds CrCl in the basic salt that has melted 36H 2O treats CrCl 36H 2O is molten fully mutually with basic salt, and stirs; Temperature control is transferred to 580～650 ℃ then, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath carry out chromising and handle, subsequently processed workpiece is taken out from salt bath, water-cooled and to clean salt residual; By percentage to the quality, described basic salt is by CaCl 246～50%, NaCl 46～50% and KCl 0～8% form.
The described basic salt temperature of fusion that mixes is 600～620 ℃.
Described pending workpiece carries out the chromising treatment time in salt bath be 3～24h.
The reaction that nanometer CrN thin film growth process of the present invention relates to is as follows:
(a) Fe of nitriding formation 2N, Fe 4N phase decomposes is to provide required N atom:
Fe 2N → Fe4N+[N] (the N atom is provided)
Fe 4N → Fe+[N] (the N atom is provided)
(b) the salt bath reaction provides Cr atom process (basic salt is not participated in reaction, and effective constituent is participated in reaction):
CrCl 36H 2O → CrCl 3+ 6H 2O ↑ (thermal dehydration)
CrCl 3+ Cr (chromium powder of adding) → CrCl 2(obtaining direct effective constituent)
CrCl 2+ Fe (base material) → [Cr] (active Cr is provided)+FeCl 2(add Fe powder balance with it, promote reaction)
(c) adds the Si powder and quicken the salt bath reaction process, thereby acceleration CrN is grain formation:
2CrCl 2+ Si → SiCl 4+ 2[Cr] (more active Cr atom is provided)
(d) generate CrN
[Cr]+[N]→CrN。
The present invention has following advantage with respect to prior art:
(1) the present invention can directly grow on steel and obtain the CrN film of nanocrystal, has the frictional coefficient of reducing effect.
(2) chromium nitride film of the present invention preparation is directly grown on steel and is formed, and the bonding force of itself and matrix is good, Heat stability is good.
(3) to prepare the chromium nitride film temperature lower in the present invention, and the film formation speed is fast, can adopt no treatment temp and treatment time according to different steel grade needs (tempering temperature according to steel is selected), saves the energy, and the industrial application degree of freedom is good.
(4) the present invention can carry out salt bath chromizing under lesser temps (minimum can at 500 ℃), has guaranteed that processed workpiece is indeformable substantially.Chromising finishes, and the salt that can adopt the mode of direct water-cooling will remain on the workpiece cleans up, and has remedied the residual shortcoming of cleaning difficulty of salt when salt bath was handled in the past like this.
(5) the present invention, Applicable temperature a wider range can be 500～650 ℃ of methods that obtain the nano silicon nitride chromium thin film, and treatment temp can directly be selected on the tempering temperature of steel, make " tempering " and " chromising " to carry out simultaneously like this, simplified heat treatment step.
(6) the present invention uses the TRD technology and carries out the material surface nanometer and handle, and obtains the nano silicon nitride chromium thin film, has proposed a kind of new material surface nanometer thinking, has widened the industrial applications prospect of chromium nitride.
Description of drawings:
Fig. 1 is embodiment 1 650 ℃ of salt bath chromizing 3h on 20 steel, the transmission electron microscope bright field image (TEM/BF) of the nano-crystal chromium nitride film that direct growth obtains, and the selected diffraction style (as upper right corner illustration) of nano-crystal chromium nitride film, the chromising compound layer of the about 6.5 μ m of the thickness that is obtained, for by grain-size 60～80nm etc. axle CrN crystal grain form.
Fig. 2 a is among the embodiment 12 behind 500 ℃ of salt bath chromizing 24h of H13 steel, obtains to be about the CrN layer (shown in C layer among the figure) of 4 μ m and the microstructure cross-sectional scans Electronic Speculum back scattering picture (SEM/QBSD) of the diffusion layer (shown in D layer among the figure) that thickness is about 20 μ m;
Fig. 2 b is corresponding with Fig. 2 a, and the K α 1 of element Cr, Fe is along chromising depth direction characteristic X-ray count distribution figure.
Embodiment:
Below in conjunction with drawings and Examples the present invention is further described, but the scope of protection of present invention is not limited to the scope that embodiment represents.
Embodiment 1
20 steel, after the normalizing treatment, pretreating surface polishes again, deoils.Carry out 540 ℃ of following ionitriding 8h then,, bell-type furnace is used in ionitriding, adopts the 50Pa rough vacuum, and medium is 0.5m 3/ h ammonia.Be chilled to room temperature with stove, 650 ℃ of following salt bath chromizing 3h are carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier melts about 620 ℃ and (adds CrCl in this temperature 36H 2O can reduce volatilization), then gradually, a small amount of in the basic salt that has melted, add CrCl lentamente in batches 36H 2O; Treat that all desires add CrCl 36H 2O is incubated to CrCl after all joining in the basic salt that has melted 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 650 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 3h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: CaCl 248%, NaCl 48%, and KCl 4%; In basic salt mass percent, effective constituent is: 200 order Cr powder 20%, Fe powder 10%, CrCl 36H 2O 50%, Si powder 10%.As shown in Figure 1, present embodiment has obtained thickness and has been approximately 6.5 μ m (metallurgical analysis result), the chromium nitride layer of being made up of at the equi-axed crystal of 60～80nm grain-size.After adding a small amount of Si in the salt bath, chromising speed is obviously accelerated, thereby has obtained nanocrystalline infiltration layer within a short period of time.
Embodiment 2
20 steel, after the normalizing treatment, pretreating surface polishes again, deoils.Carry out 540 ℃ of following ionitriding 8h then,, bell-type furnace is used in ionitriding, adopts the 50Pa rough vacuum, and medium is 0.5m 3/ h ammonia.Be chilled to room temperature with stove, 650 ℃ of following salt bath chromizing 6h are carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier melts about 620 ℃ and (adds CrCl in this temperature 36H 2O can reduce volatilization), then gradually, a small amount of in the basic salt that has melted, add CrCl lentamente in batches 36H 2O; Treat that all desires add CrCl 36H 2O is incubated to CrCl after all joining in the basic salt that has melted 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 650 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 6h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: CaCl 250%, NaCl 50%; In basic salt mass percent, effective constituent is: 200 order Cr powder 20%, Fe powder 10%, CrCl 36H 2O 50%, Si powder 5%.Obtained thickness and be approximately 6.5 μ m (metallurgical analysis result), grain-size is the nano-crystal chromium nitride layer (XRD calculation result) of 90～110nm.
Embodiment 3
20 steel, after the normalizing treatment, pretreating surface polishes again, deoils.Carry out 540 ℃ of following ionitriding 8h then,, bell-type furnace is used in ionitriding, adopts the 50Pa rough vacuum, and medium is 0.5m 3/ h ammonia.Be chilled to room temperature with stove, 580 ℃ of following salt bath chromizing 12h are carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier (adds CrCl in this temperature 620 ℃ of fusings 36H 2O can reduce volatilization), then gradually, a small amount of in the basic salt that has melted, add CrCl lentamente in batches 36H 2O; Treat that all desires add CrCl 36H 2O is incubated to CrCl after all joining in the basic salt that has melted 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 580 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 12h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: CaCl 246%, NaCl 46%, and KCl 8%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 25%, Si powder 5%.Obtained thickness and be approximately 6 μ m (metallurgical analysis result), grain-size is the chromium nitride layer (XRD calculation result) of 70～90nm.
Embodiment 4
The T10 steel, after the modifier treatment, pretreating surface polishes again, deoils.Carry out 540 ℃ of following ionitriding 8h then,, bell-type furnace is used in ionitriding, adopts the 50Pa rough vacuum, and medium is 0.5m 3/ h ammonia.Be chilled to room temperature with stove, 580 ℃ of following salt bath chromizing 8h are carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier (adds CrCl in this temperature 620 ℃ of fusings 36H 2O can reduce volatilization), then gradually, a small amount of in the basic salt that has melted, add CrCl lentamente in batches 36H 2O; Treat that all desires add CrCl 36H 2O is incubated to CrCl after all joining in the basic salt that has melted 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 580 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 8h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: CaCl 246%, NaCl 46%, and KCl 8%; In basic salt mass percent, effective constituent is: 200 order Cr powder 15%, Fe powder 7%, CrCl 36H 2O 30%, Si powder 7%.Obtained thickness and be approximately 6.7 μ m (metallurgical analysis result), grain-size is at the chromium nitride layer (XRD calculation result) of 70～90nm.
Embodiment 5
The T10 steel, through modifier treatment, and pretreating surface, polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 3h under 650 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCi 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 650 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 3h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 6 μ m (metallurgical analysis result), grain-size is the chromium nitride layer (XRD calculation result) of 70～90nm.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 20%, Fe powder 10%, CrCl 36H 2O50%, Si powder 5%.
Embodiment 6
The T10 steel, modifier treatment, the pretreating surface polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 6h under 550 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 550 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 6h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 6.2 μ m (metallurgical analysis result), grain-size is in 60～80nm chromium nitride layer (XRD calculation result).By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl25%, BaCl 235%, CaCl 240%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 30%, Si powder 7%.
Embodiment 7
The T10 steel, modifier treatment, the pretreating surface polishing is deoiled, and carries out 650 ℃ of following gas nitridings (adopt pit furnace, ammonia decomposition is 85%) 3h, the oil cooling of coming out of the stove, salt bath chromizing 6h under 550 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 550 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 6h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 4 μ m (metallurgical analysis result), grain-size is 50～70nm chromium nitride layer (an XRD calculation result).By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl25%, BaCl 235%, CaCl 240%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 30%, Si powder 10%.
Embodiment 8
45 steel, anneal, the pretreating surface polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 6h under 550 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 550 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 6h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 7 μ m (metallurgical analysis result), grain-size is 60～80nm chromium nitride layer (tem observation result).By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 20%, Fe powder 10%, CrCl 36H 2O 30%, Si powder 5%.
Embodiment 9
45 steel, anneal, the pretreating surface polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 4h under 550 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 550 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 3h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 6.5 μ m (metallurgical analysis result), grain-size is the chromium nitride layer (tem observation result) of 50～80nm.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 20%, Fe powder 10%, CrCl 36H 2O 30%, Si powder 10%.
Embodiment 10
45 steel, anneal, the pretreating surface polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 24h under 500 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 500 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 24h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 8.4 μ m (metallurgical analysis result), grain-size is 70～80nm chromium nitride layer (tem observation result).By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl 20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 25%, Si powder 10%.Originally 500 ℃ because speed of response is very slow, at short notice can't chromising, add a small amount of Si after chromising speed obviously accelerate.The frictional coefficient test shows that the CrN crystal grain of this kind nanocrystal composition obtains the infiltration layer frictional coefficient little (with the reciprocal metal to-metal contact mode of the Ball on disc test result of Optimol SRV4 type frictional behaviour test macro) of the thicker CrN crystal grain composition of (610 ℃ of chromising 24h) than method of the same race.
Embodiment 11
Pure iron, anneal, the pretreating surface polishing is deoiled, and (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and salt bath chromizing 24h under 500 ℃ of temperature is carried out after doing slightly to clean again in the surface.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 600 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 500 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 24h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.Obtained thickness and be approximately 9 μ m (metallurgical analysis result), grain-size is the chromium nitride layer (tem observation result) of 70～90nm.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl 20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 25%, Si powder 10%.
Embodiment 12
The H13 steel is 1030 ℃ of vacuum hardenings, 550 ℃ of tempering once, the pretreating surface polishing is deoiled, (use bell-type furnace, adopt the 50Pa rough vacuum, medium is 0.5m to carry out 560 ℃ of following ionitridings 3/ h ammonia) 5.5h is chilled to room temperature with stove, and sand papering is used on the surface slightly, carries out 500 ℃ of following salt bath chromizing 24h again.The salt bath chromizing step is: the basic salt that will mix in crucible furnace earlier is 610 ℃ of fusings, then gradually, add CrCl lentamente in the basic salt that has melted on a small quantity in batches 36H 2O; Treat that all desires add CrCl 36H 2After O all joined in the basic salt that has melted, CrCl was treated in insulation 36H 2O is molten fully mutually with basic salt, and stirs; Then temperature control is transferred to 500 ℃ of pretreatment temperatures, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, leave standstill about 30 minutes, pending workpiece is put into salt bath; Behind the insulation 24h, rapidly workpiece is taken out from salt bath, direct water-cooling is residual to clean salt.By percentage to the quality, the salt bath chromizing prescription is in the present embodiment: basic salt: NaCl 20%, BaCl 230%, CaCl 250%; In basic salt mass percent, effective constituent is: 200 order Cr powder 10%, Fe powder 5%, CrCl 36H 2O 25%, Si powder 10%.It is 20～50nm that present embodiment has obtained with grain-size, thickness is approximately the single-phase CrN layer (the C layer shown in Fig. 2 a) of 4 μ m, and along the distribution plan (shown in Fig. 2 b) of chromising depth direction as can be known by the characteristic X-ray of element Cr, Fe counting, below single-phase CrN layer, form a layer thickness and be approximately 20 μ m (corresponding D layer shown in Fig. 2 a) diffusion layer, the tem observation result shows that this diffusion layer is the CrN of 60～80nm and the α-Fe phase composite of big grain-size by grain-size.Test shows, though when not adding the Si powder at 600 ℃, the chromising effect is also bad, add an amount of Si powder after, obtain infiltration layer preferably at 500 ℃.The frictional coefficient test shows that the CrN crystal grain of this kind nanocrystal composition obtains the infiltration layer frictional coefficient little (with the reciprocal metal to-metal contact mode of the Ball on disc test result of Optimol SRV4 type frictional behaviour test macro) of the thicker CrN crystal grain composition of (700 ℃ of chromising 12h) than method of the same race.

Claims (6)

1, a kind of directly method of growing nano-crystal chromium nitride film on steel is characterized in that comprising the steps:
(1) nitriding is handled, and steel is carried out nitriding handle after just handling;
(2) salt bath chromizing is handled, and the steel after step (1) is handled carry out 500 ℃～650 ℃ following salt bath chromizings again and handle after being chilled to room temperature and doing the surface and cleaning; Salt bath formula is made up of basic salt prescription and effective constituent prescription; By percentage to the quality, wherein basic salt is by NaCl 20～25%, BaCl 230～35% and CaCl 240～50% form; In basic salt mass percent, effective constituent is: 200 order Cr powder 10～20%, Fe powder 5～10%, CrCl 36H 2O 25～50% and Si powder 5～10%;
Or salt bath chromizing is treated to: the steel after step (1) is handled carry out chromising again and handle after being chilled to room temperature and doing the surface and cleaning under 580～650 ℃ of treatment temps, salt bath formula is made up of basic salt prescription and effective constituent prescription; By percentage to the quality, wherein said basic salt is by CaCl 246～50%, NaCl 46～50% and KCl 0～8% form; In basic salt mass percent, effective constituent is: 200 order Cr powder 10～20%, Fe powder 5～10%, CrCl 36H 2O 25～50% and Si powder 5～10%.
2, a kind of directly method of growing nano-crystal chromium nitride film on steel according to claim 1 is characterized in that described nitriding is treated to ionitriding or gas nitriding.
3, a kind of directly method of growing nano-crystal chromium nitride film on steel according to claim 1 is characterized in that it is to carry out nitriding to handle under 540～650 ℃ of treatment temps that described nitriding is handled.
4, a kind of directly method of growing nano-crystal chromium nitride film on steel according to claim 1 is characterized in that described salt bath chromizing treatment process is: the basic salt fusing that will mix in crucible furnace earlier adds CrCl in the basic salt that has melted 36H 2O treats CrCl 36H2O is molten fully mutually with basic salt, and stirs; Temperature is transferred to 580～650 ℃ then, Cr powder, Fe powder and the Si powder that mixes added in the salt bath, and stir, left standstill 20～30 minutes, pending workpiece is put into salt bath carry out chromising and handle, subsequently processed workpiece is taken out from salt bath, water-cooled and to clean salt residual; By percentage to the quality, described basic salt is by CaCl 246～50%, NaCl 46～50% and KCl 0～8% form.
5, a kind of directly method of growing nano-crystal chromium nitride film on steel according to claim 4 is characterized in that the described basic salt temperature of fusion that mixes is 600～620 ℃.
6, a kind of directly method of growing nano-crystal chromium nitride film on steel according to claim 4 is characterized in that described processed workpiece carries out the chromising treatment time in salt bath be 3～24h.
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