Method for producing a ceramic layer on a transition metal surface by means of iron layer-mediated carburization

Abstract

The application discloses a method for preparing a ceramic layer on a transition metal surface by iron interlayer carburizing. The method comprises the following steps: firstly, an iron layer is prepared on the surface of the transition metal by surface technology without melting the surface of the transition metal; then, the iron layer is carburized, so that the iron layer is converted into a high-carbon steel layer, a large number of interstitial carbon atoms and a small amount of iron atoms in the high-carbon steel layer diffuse into the surface layer of the transition metal, and a carbide ceramic layer with the solid-solution iron atoms is formed on the surface layer; finally, the surface is immersed into a corrosion liquid to remove the high-carbon steel layer on the surface, so that the carbide ceramic layer is exposed on the surface. Compared with a traditional carburizing method, the method can improve the density, growth rate and hardness of the ceramic layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal material surface treatment method, and relates to a method for preparing a transition metal surface ceramic layer through iron layer medium carburization. BACKGROUND

[0002] With the rapid development of manufacturing industry, the increasingly wide application range of transition metals and increasingly harsh service environment put forward higher requirements for the surface strength, hardness and wear resistance of the transition metals, and the preparation of ceramic layers on the surface of the transition metals can improve the surface strength, hardness and wear resistance of the transition metals and prolong the service life of the materials, which is an effective means to improve the surface performance of the transition metals.

[0003] Carburization is one of the methods for preparing ceramic layers on the surface of transition metals, and the carburization of transition metals can make carbon react with the surface of the transition metals to form a surface carbide ceramic layer, and the interface bonding force between the formed carbide and the matrix is good because of the in-situ reaction between carbon and metal; the interface bonding strength between the obtained carbide layer and the matrix is high because of the diffusion of carbon atoms into the matrix.

[0004] Common carburization methods mainly include gas carburization and solid carburization, and the gas carburization needs to pass carbon-containing gas into a high-temperature furnace to decompose the carbon-containing gas at high temperature, so that the free carbon atoms formed are absorbed by the surface of the sample and diffuse into the interior to form a carbide ceramic layer growing into the matrix, and the solid carburization usually seals the workpiece and carbon-containing solid powder in a sealed container, and heats the solid powder to decompose the solid powder into carbon-containing gas and further generate free carbon atoms to carburize the workpiece, and the basic principles of the two carburization methods are the same, that is, the carbon source is decomposed into carbon-containing gas and further decomposed into free carbon, which makes the carburization method have good applicability to workpieces with special-shaped surfaces.

[0005] However, the optimal temperature range for preparing the transition metal surface ceramic layer through carburization is small, and the thickness of the carbide layer prepared in the optimal range is too small, which restricts the improvement of the surface hardness. When the temperature or carbon potential is too low, the formed carbide layer is too thin, and even the carbide layer cannot be formed; when the temperature or carbon potential is too high, the carbide grains are coarse, and the carbide layer has a large number of pores, which affects the surface mechanical properties. Therefore, the performance of the transition metal surface ceramic layer prepared by the traditional carburization method has reached a bottleneck. SUMMARY

[0006] The application aims to provide a method for preparing a transition metal surface ceramic layer through iron layer medium carburization, which solves the problem that the ceramic layer is prone to have pores when the transition metal surface ceramic layer is prepared through traditional carburization, and improves the surface hardness of the ceramic layer.

[0007] The application discloses a method for preparing a ceramic layer on a transition metal surface by using an iron layer medium carburization process.

[0008] Step 1, preparing a transition metal, first performing surface pretreatment on the transition metal, and then using a surface treatment process to prepare an iron layer on the surface of the pretreated transition metal to obtain the transition metal with the iron layer;

[0009] Step 2, performing carburization treatment on the transition metal with the iron layer to obtain a carbide ceramic layer with a high-carbon steel layer;

[0010] Step 3, removing the high-carbon steel layer by using a corrosion solution to finally obtain the carbide ceramic layer on the surface of the transition metal.

[0011] The application also has the following characteristics:

[0012] In step 1, the transition metal is one of Ti, Zr, Nb, Ta, W, Cr and Mo or an alloy with the above as main chemical components;

[0013] In step 1, the surface treatment process is one of physical vapor deposition, chemical vapor deposition, electroplating and chemical plating;

[0014] In step 1, the mass fraction of iron in the iron layer ranges from 98% to 99.9999%, and the thickness of the iron layer ranges from 1 μm to 100 μm;

[0015] In step 2, the carburization treatment is any one of solid carburization, gas carburization, vacuum carburization and plasma carburization, the temperature range of the carburization treatment is 800-1300 DEG C, and the time of the carburization treatment is 2-48 h;

[0016] In step 3, the corrosion solution is specifically a hydrochloric acid solution or a sulfuric acid solution, the mass fraction of hydrochloric acid in the hydrochloric acid solution ranges from 18% to 28%, and the mass fraction of sulfuric acid in the sulfuric acid solution ranges from 45% to 60%.

[0017] The application has the following beneficial effects:

[0018] (1) Compared with the traditional carburization method, the absorption efficiency of active carbon atoms by the iron layer is higher than that of the transition metal, and the iron elements diffused into the surface can effectively increase the growth rate of the ceramic layer, so that the growth rate of the ceramic layer is obviously improved;

[0019] (2) The solid solubility of carbon in the prepared pure iron or layer has an upper limit, and when the carbon potential is too high, the carbon potential on the surface of the transition metal will not exceed the upper limit of the solid solubility, so that the problem of loose and porous ceramic layer caused by the too high carbon potential can be prevented;

[0020] (3) The present application uses carburizing to convert the surface of transition metal into a ceramic layer, so that the ceramic phase is precipitated in situ, the grain boundary bonding force is high, the ceramic phase grows into the matrix, that is, the film-matrix interface (ceramic / metal interface) is in the surface layer of the metal matrix, the film-matrix interface has high bonding strength, and at the same time, the carbide ceramic layer can be prepared on a non-planar surface (such as a curved surface, an inner hole, etc.);

[0021] (4) The iron layer on the surface of the metal matrix can prevent the oxidation of the transition metal during the gas / solid carburizing process. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a preparation flowchart of the method for preparing a ceramic layer on the surface of a transition metal by iron layer-mediated carburizing according to the present application. DETAILED DESCRIPTION

[0023] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0024] The method for preparing a ceramic layer on the surface of a transition metal by iron layer-mediated carburizing according to the present application specifically comprises the following steps:

[0025] Step 1: Prepare a piece of transition metal, first pretreat the surface of the transition metal, the transition metal is pure metal or an alloy with one of Ti, Zr, Nb, Ta, W, Cr, Mo as the main chemical component, and then use a surface treatment process to prepare an iron layer on the surface of the pretreated transition metal, to obtain a transition metal with an iron layer on the surface, the surface treatment process is one of physical vapor deposition, chemical vapor deposition, electroplating, and electroless plating, the mass fraction of iron in the iron layer ranges from 98% to 99.9999%, and the thickness of the iron layer ranges from 1 μm to 100 μm;

[0026] Step 2: Carburize the transition metal with an iron layer on the surface, so that the surface iron layer is converted into a high-carbon steel layer, and at the same time, the high-concentration interstitial carbon atoms and a small amount of iron atoms in the high-carbon steel layer diffuse into the surface layer of the transition metal, so that the surface layer of the transition metal is converted into a carbide ceramic layer with dissolved iron elements, the carburizing temperature ranges from 800 to 1300℃, the carburizing time ranges from 2 to 48 h, preferably, the carburizing method is gas carburizing or solid carburizing, the carburizing treatment temperature ranges from 900℃ to 1200℃, and more preferably, the carburizing treatment temperature ranges from 1000℃ to 1150℃;

[0027] Step 3: Remove the high-carbon steel layer using a corrosion solution, and finally obtain a carbide ceramic layer on the surface of the transition metal, the corrosion solution is selected from hydrochloric acid solution and sulfuric acid solution, the mass fraction of hydrochloric acid in the hydrochloric acid solution is 18%-28%, and the mass fraction of sulfuric acid in the sulfuric acid solution is 45%-60%.

[0028] In the present application, the iron layer is prepared on the surface of the transition metal before carburizing. This layer is not the required structure of the surface of the final product, but the required structure in the preparation process, and therefore needs to be removed after the end of carburizing. The iron layer plays three roles in the carburizing process: 1) has a "catalytic" and "buffering" effect. The iron layer acts as an intermediate medium to separate the active carbon atmosphere from the surface of the transition metal. Since the absorption efficiency of the iron layer for active carbon atoms is higher than that of the transition metal for active carbon atoms, and the efficiency of carbon atoms passing through the interface between iron and transition metal is high, the absorption efficiency of the transition metal for active carbon atoms can be significantly improved at lower temperatures and lower carbon potentials, playing a "catalytic" role. At the same time, the solid solubility of carbon in the surface-prepared iron layer has an upper limit. When the carbon potential is too high, the carbon potential on the surface of the transition metal will not exceed the upper limit of its solid solubility, thus preventing the problem of loose and porous carbide ceramic layer caused by excessive carbon potential, playing a "buffering" role; 2) iron atoms diffuse into the surface at the same time as carburizing. The doping of iron elements can effectively increase the growth rate of the ceramic layer and improve the density of the ceramic layer; 3) the iron layer on the surface of the metal matrix can prevent the oxidation of the transition metal during the gas / solid carburizing process.

[0029] Example 1:

[0030] The present example includes the following steps:

[0031] Step 1: Prepare a piece of tungsten metal plate. First, perform surface pretreatment on the tungsten metal plate. The purity of the tungsten metal plate is 99.9wt%. The surface pretreatment is grinding and polishing, then clean it with acetone and alcohol in an ultrasonic wave. Use magnetron sputtering to prepare an iron layer on the surface of the tungsten metal (W). The obtained tungsten metal with an iron layer on the surface has an iron mass fraction of 99.9999% and a thickness of 100μm.

[0032] Step 2: Perform solid carburizing on the tungsten metal with an iron layer on the surface obtained in step 1. Bury the sample in a carburizing agent (90wt% of carbon black powder and 10wt% of sodium carbonate powder) in a carburizing pot, then seal the carburizing pot and place it in a high-temperature heat treatment furnace to heat to the carburizing temperature and keep it for a certain time. The carburizing temperature is 1300℃, and the carburizing time is 48h. After carburizing, the workpiece is cooled to room temperature in the furnace;

[0033] Step 3: Immerse the workpiece obtained in step 2 in a hydrochloric acid solution. When there is no gas bubble, take out the workpiece. The high-carbon steel layer is completely removed, and the ceramic layer is exposed on the surface. Finally, a WC ceramic layer with solid-solution iron elements is obtained on the surface of the tungsten metal.

[0034] The WC ceramic layer obtained by the above method has the following characteristics: 1) the ceramic layer is dense and pore-free; 2) the volume fraction of WC in the ceramic layer is high (about 100%), and iron atoms are dissolved in the WC; 3) the ceramic layer is uniform in thickness and has no oxidation phenomenon; 4) the surface hardness can reach 2800HV; 5) the film-base bonding force is greater than 100N; 6) the surface wear resistance of the metal tungsten is greatly improved (more than 30 times higher than that of the metal tungsten).

[0035] Example 2

[0036] The present example includes the following steps:

[0037] Step 1: Prepare a curved titanium alloy, first perform surface pretreatment on the curved titanium alloy, the surface pretreatment is grinding and polishing, then clean with acetone and alcohol in an ultrasonic wave, and prepare an iron layer on the surface of the curved titanium alloy (Ti6Al4V) by electroplating to obtain a titanium alloy substrate with an iron layer on the surface, the mass fraction of iron in the iron layer is 98%, and the thickness of the iron layer is 10μm;

[0038] Step 2: Perform gas carburizing on the titanium alloy substrate with the iron layer obtained in step 1, place the workpiece in a carburizing furnace and introduce carburizing medium (kerosene, toluene, methanol, ethanol) gas, the carburizing temperature is 800℃, the carburizing time is 48h, the surface iron layer is converted into a high-carbon steel layer, and at the same time the surface layer of the titanium alloy is converted into a TiC ceramic layer with dissolved iron elements, and the workpiece is cooled to room temperature in the furnace after carburizing is completed;

[0039] Step 3: immerse the workpiece after carburizing in a sulfuric acid solution, and take out the workpiece when no bubbles come out, the high-carbon steel layer is completely removed, and the ceramic layer is exposed on the surface, and finally a TiC ceramic layer with dissolved iron atoms is obtained on the surface of the titanium alloy.

[0040] The Ti6Al4V surface ceramic layer obtained by the above method has the following characteristics: 1) the ceramic layer is dense and pore-free; 2) the volume fraction of TiC in the ceramic layer is high (about 100%), and iron atoms are dissolved in the TiC; 3) the ceramic layer is uniform in thickness and has no oxidation phenomenon; 4) the surface hardness can reach 2600HV; 5) the ceramic layer and the metal substrate have a bonding force greater than 100N; 6) the surface wear resistance of the Ti6Al4V is greatly improved (more than 28 times higher than that of the Ti6Al4V).

[0041] Example 3

[0042] The present example includes the following steps:

[0043] Step 1: Prepare a piece of metal tantalum plate, first surface pretreatment of the curved titanium alloy, surface pretreatment is polishing, polishing, then respectively in the ultrasonic wave with acetone, alcohol cleaning, using the method of atmospheric pressure chemical vapor deposition in the surface of the metal tantalum plate prepared iron layer, the surface of the metal tantalum plate with iron layer, iron layer in the iron element mass fraction is 99.9%, thickness 1 μm;

[0044] Step 2: the surface of the metal tantalum with iron layer obtained in step 1 is solid carburized. The sample is buried in the carburizing agent (95wt% of carbon black powder and 5wt% of sodium carbonate powder) in the carburizing pot, then the carburizing pot is sealed and placed in a high temperature heat treatment furnace for heating. As the temperature rises, carbon atoms diffuse inward and convert the pure iron layer into high carbon steel, and then a large number of carbon atoms and a small amount of iron atoms in the high carbon steel diffuse into the shaped surface metal matrix, converting the surface of the matrix into a TaC ceramic layer with solid solution iron elements, the carburizing temperature is 1150℃, and the carburizing time is 2h. After carburizing, the workpiece is cooled to room temperature in the furnace;

[0045] Step 3: after the end of carburizing, the workpiece is immersed in hydrochloric acid solution, and when there is no bubble, the workpiece is taken out, the high carbon steel layer is completely removed, and the ceramic layer is exposed on the surface, finally a TaC ceramic layer with solid solution iron atoms is obtained on the surface of the metal tantalum.

[0046] By the above method, the ceramic layer obtained has the following characteristics: 1) the ceramic layer is dense and pore-free; 2) the volume fraction of TaC in the ceramic layer is close to 100%, and iron atoms are solid-solved in the TaC; 3) the ceramic layer is uniform in thickness and has no oxidation phenomenon; 4) the surface hardness can reach 2200HV; 5) the bonding force between the ceramic layer and the metal tantalum is greater than 120N; 6) the surface wear resistance of the metal tantalum is greatly improved (more than 20 times higher than that of the metal tantalum).

[0047] Example 4:

[0048] The present example includes the following steps:

[0049] Step 1: Prepare a piece of metal niobium plate, first surface pretreatment of the metal niobium plate, the purity of the metal niobium plate is 99.9wt%, the surface pretreatment is polishing, polishing, then respectively in the ultrasonic wave with acetone, alcohol cleaning, using the method of chemical plating to prepare pure iron metal layer on the surface of the metal niobium (Nb) workpiece, obtain the surface of the metal niobium with iron layer, iron layer in the iron element mass fraction is 99.0%, thickness 5 μm;

[0050] Step 2: the surface of the metal niobium with iron layer obtained in step 1 is solid carburized. The workpiece is buried in the carburizing agent (80wt% of carbon black powder and 20wt% of sodium carbonate powder) in the carburizing pot, then the carburizing pot is sealed and placed in a high temperature heat treatment furnace for heating. The carburizing temperature is 1000℃, and the carburizing time is 10h. After carburizing, the workpiece is cooled to room temperature in the furnace;

[0051] Step 3: immerse the workpiece after carburizing into nitric acid solution, and take it out when there is no bubble, the high carbon steel layer is completely removed, and the ceramic layer is exposed on the surface, finally obtaining the NbC ceramic layer with solid solution iron atoms on the surface of the metal niobium.

[0052] Through the above method, the ceramic layer obtained has the following characteristics: 1) the ceramic layer is dense and pore-free; 2) the volume fraction of NbC in the ceramic layer is close to 100%, and the iron atoms are solid-solved in the NbC; 3) the thickness of the ceramic layer is uniform, and there is no oxidation phenomenon; 4) the surface hardness can reach 2000HV; 5) the bonding force between the NbC ceramic layer and the metal niobium is greater than 100N; 6) the surface wear resistance of the metal niobium is greatly improved (more than 16 times higher than that of the metal niobium).

[0053] Example 5:

[0054] The present example includes the following steps:

[0055] Step 1: prepare a metal zirconium plate, first perform surface pretreatment on the metal zirconium plate, the purity of the metal zirconium plate is 99.9wt%, the surface pretreatment is grinding and polishing, then clean it with acetone and alcohol in ultrasonic wave, prepare an iron layer on the surface of the metal zirconium plate by cathodic arc ion plating, obtain a metal zirconium plate with an iron layer on the surface, the volume fraction of iron in the iron layer is 99.99%, and the thickness of the iron layer is 50μm;

[0056] Step 2: solid carburize the metal zirconium plate with an iron layer obtained in step 1. Bury the sample in carburizing agent (80wt% carbon black powder and 20wt% sodium carbonate powder) in a carburizing pot, then seal the carburizing pot and place it in a high-temperature heat treatment furnace for heating, the carburizing temperature is 1150℃, and the carburizing time is 8h. After carburizing, the workpiece is cooled to room temperature in the furnace;

[0057] Step 3: immerse the workpiece after carburizing into nitric acid solution, and take it out when there is no bubble, the high carbon steel layer is completely removed, and the ceramic layer is exposed on the surface, finally obtaining the NbC ceramic layer with solid solution iron atoms on the surface of the metal niobium.

[0058] Through the above method, the ceramic layer obtained has the following characteristics: 1) the ceramic layer is dense and pore-free; 2) the volume fraction of NbC in the ceramic layer is close to 100%, and the iron atoms are solid-solved in the NbC; 3) the thickness of the ceramic layer is uniform, and there is no oxidation phenomenon; 4) the surface hardness can reach 2000HV; 5) the bonding force between the NbC ceramic layer and the metal niobium is greater than 100N; 6) the surface wear resistance of the metal niobium is greatly improved (more than 16 times higher than that of the metal niobium).

[0059] The mechanical property test of the transition metal surface ceramic layer prepared by carbon iron co-permeation prepared in the embodiments 1-5 is carried out, and the test results are as follows:

[0060]

[0061]

[0062] Through the above method, the film-base bonding force of the transition metal surface ceramic layer prepared by carbon iron co-permeation is 100N-120N, and the mechanical property is better; the film-base bonding force of the CrN coating layer on the steel surface prepared by cathode arc evaporation deposition in the prior art is 65-90N, compared with the prior art, the film-base bonding force of the transition metal surface ceramic layer prepared by carbon iron co-permeation is obviously improved, the surface hardness of the transition metal surface ceramic layer prepared by carbon iron co-permeation is 1700HV-2800HV, the surface hardness of the CrN coating layer on the steel surface prepared by cathode arc evaporation deposition is 1700-2300HV, the surface hardness obtained by carbon iron co-permeation is higher, and the wear resistance is better, so it can be seen that the film-base interface bonding strength of the transition metal surface ceramic layer prepared by carbon iron co-permeation is high, and the surface of the ceramic layer obtained has better wear resistance.

Claims

1. A method for producing a ceramic layer on a surface of a transition metal by means of carburization of an iron-based medium, characterized in that, The method is implemented according to the following steps: Step 1: surface pretreatment of the transition metal, iron layer is prepared on the surface of the pretreated transition metal by surface treatment process, and the transition metal with iron layer on the surface is obtained; Step 2: carburizing treatment is performed on the transition metal with iron layer on the surface to obtain a carbide ceramic layer with high carbon steel layer on the outer layer; Step 3: the high carbon steel layer is removed by using an etching solution, and finally a carbide ceramic layer is formed on the surface of the transition metal.

2. The method of claim 1 wherein the iron-group interstitial medium carburization to produce a ceramic layer on a transition metal surface is characterized by, The transition metal in step 1 is one of Ti, Zr, Nb, Ta, W, Cr, Mo or an alloy with them as the main chemical components.

3. The method of claim 1 wherein the iron-based media carburization process is characterized by, In step 1, the surface treatment process is one of physical vapor deposition, chemical vapor deposition, electroplating, and chemical plating.

4. The method of claim 1 wherein the iron-based media carburization process is characterized by, The mass fraction of iron in the iron layer in step 1 is 98%-99.9999%, and the thickness of the iron layer is 1-100 μm.

5. The method of claim 1 wherein the iron-based media carburization process is characterized by, In step 2, the carburizing treatment is any one of solid carburizing, gas carburizing, vacuum carburizing and plasma carburizing, the temperature range of carburizing treatment is 800-1300 ℃, and the carburizing treatment time is 2-48 h.

6. The method of claim 1 wherein the iron-based media carburization process is characterized by, The etching solution in step 3 is specifically hydrochloric acid solution or sulfuric acid solution, the mass fraction of hydrochloric acid in the hydrochloric acid solution is 18%-28%, and the mass fraction of sulfuric acid in the sulfuric acid solution is 45%-60%.

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