CN111979513B - Preparation method of low-temperature boronized ductile iron wear-resistant surface - Google Patents

Preparation method of low-temperature boronized ductile iron wear-resistant surface Download PDF

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CN111979513B
CN111979513B CN202010737204.9A CN202010737204A CN111979513B CN 111979513 B CN111979513 B CN 111979513B CN 202010737204 A CN202010737204 A CN 202010737204A CN 111979513 B CN111979513 B CN 111979513B
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boronizing
cast iron
nodular cast
boriding
mass
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CN111979513A (en
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张东亚
孙喜洲
高峰
李艳
孔令飞
税琳棋
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Xian University of Technology
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/60—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes
    • C23C8/62—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using solids, e.g. powders, pastes only one element being applied
    • C23C8/68—Boronising
    • C23C8/70—Boronising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
    • C23C22/08—Orthophosphates
    • C23C22/12—Orthophosphates containing zinc cations
    • C23C22/17—Orthophosphates containing zinc cations containing also organic acids
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated

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  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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  • Mechanical Engineering (AREA)
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Abstract

The invention discloses a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron, which comprises the following steps of firstly, pretreating the nodular cast iron; then preparing a powder boronizing agent and a sealing material; boronizing treatment: firstly, carrying out pre-boronizing treatment on an iron container to be used as a boronizing tank, namely filling a boronizing agent into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and then cooling; filling the boriding tank which is subjected to pre-boriding with a boriding agent which is uniformly mixed, burying the pretreated nodular cast iron sample in the boriding agent, filling and compacting the boriding agent in the whole tank, and finally sealing by using the prepared sealing material; and heating the sealed container to 200-400 ℃, preserving heat for 1-2 hours, controlling the boronizing time to be 1-24 hours, and finally carrying out boronizing post-treatment to finally obtain a high-hardness boronized surface. The method can obtain a large-thickness and uniform cementation layer while reducing the boriding temperature, and effectively improve the microhardness and the wear resistance of the nodular cast iron.

Description

Preparation method of low-temperature boronized ductile cast iron wear-resistant surface
Technical Field
The invention belongs to the technical field of surface treatment of nodular cast iron, and particularly relates to a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron.
Background
The nodular cast iron is rich in graphite, forms a transfer film in a friction process, has a good antifriction effect, and is widely applied to key precision moving parts such as automobile transmission shafts, machine tool guide rails and the like. However, ductile iron has low hardness, and when subjected to high load, the matrix undergoes severe plastic deformation, resulting in severe adhesive wear. Therefore, a surface strengthening process for improving the wear resistance of the nodular cast iron is urgently needed.
Boronizing is a common heat treatment process, and the hardness, corrosion resistance, and wear resistance of the boronized surface are far from comparable to those of a generally hardened surface. Forming Fe on the surface layer by boriding the steel/iron base surface 2 The B/FeB high-hardness surface layer improves the hardness of a friction pair, obtains a surface with good wear resistance, and improves the heat resistance and the corrosion resistance. By regulating boridingThe process can also realize the regulation and control preparation of physical parameters such as hardness, thickness and the like of the boronizing layer. The boronizing mode includes solid boronizing, gas boronizing, salt bath boronizing, etc., wherein the solid boronizing is widely applied in production due to the advantages of convenient operation, good reusability of the boronizing agent, low cost, easy control of the thickness and the organization of a boronized layer, etc. However, the traditional boronizing process is carried out in a high-temperature (above 950 ℃), the thermal deformation of parts is increased, and the application of the nodular cast iron to precise moving parts is greatly limited.
Disclosure of Invention
The invention aims to provide a method for preparing a wear-resistant surface of low-temperature boronized ductile cast iron, which can obtain a large-thickness uniform cementation layer while reducing the boronizing temperature and effectively improve the microhardness and the wear resistance of the ductile cast iron.
The technical scheme adopted by the invention is that the preparation method of the low-temperature boriding wear-resistant surface of the ductile cast iron is implemented according to the following steps:
step 1, pretreating nodular cast iron;
step 2, preparing a powder boronizing agent and a sealing material;
step 3, boronizing treatment;
and 4, carrying out boronizing post-treatment to finally obtain a high-hardness boronized surface.
The present invention is also characterized in that,
the pretreatment in step 1 comprises:
step 1.1, sequentially using 600#, 800#, 1000# and 1200# metallographic abrasive paper to polish nodular cast iron, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
and step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in the step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion.
In the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 5-10 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 10-15 minutes by using absolute ethyl alcohol as a solvent.
When the phosphating solution for the nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 4-10% by mass of phosphoric acid, 5-15% by mass of nitrate, 3-8% by mass of zinc oxide, 2-10% by mass of citric acid, 1-5% by mass of a stabilizer and the balance of water, and the temperature is controlled to be 10-70 ℃ and the time is 5-30 minutes when the phosphating solution for the nodular cast iron is subjected to surface activation treatment.
In the step 2, the powder boronizing agent is prepared by taking 3-10% of boron carbide, 5-10% of potassium fluoborate, 3-5% of activated carbon and 80-90% of silicon carbide as raw materials in mass backup ratio, uniformly mixing by adopting a ball milling mode, then heating and drying, and then adding 1-2% of rare earth oxide in mass ratio.
In the step 2, the ball milling time is 6-20 hours, the ball milling rotating speed is 200-500 rpm, the boronizing agent is dried in a vacuum drying environment after ball milling, the drying time is controlled to be 60-120 minutes, and the temperature is controlled to be 120-150 ℃.
In the step 2, the sealing material is prepared by mixing 10-20% of water glass serving as a cementing material, 1-5% of sodium fluosilicate serving as an accelerant and 50-75% of clay serving as a base material in percentage by mass.
The step 3 is as follows:
step 3.1, performing pre-boronizing treatment on the iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and cooling;
3.2, filling and mixing the boriding medium prepared in the step 1 uniformly in a boriding tank which completes the pre-boriding, burying the nodular cast iron sample pretreated in the step 1 in the boriding medium, filling and compacting the boriding medium in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
and 3.3, heating the sealed container to 200-400 ℃, preserving heat for 1-2 hours, removing water in the sealing material and the boronizing agent, then vacuumizing to 10-100 Pa, controlling the furnace temperature to 550-800 ℃, and controlling the boronizing time to 1-24 hours.
In step 3.2, a 15-20mm gap is kept between the sample and the box wall.
The step 4 is as follows:
4.1, roughly polishing to remove boriding agent particles attached to the surface of the boriding sample, and finely polishing until the surface roughness Ra = 1.6-3.2 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 15-20 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.
The invention has the beneficial effects that the preparation method of the wear-resistant surface of the ductile cast iron subjected to low-temperature boronizing provides a synergistic process of a technique of surface activation treatment of a carburized layer and a rare earth catalysis technique, reduces the boronizing temperature of solid boronizing, and realizes the low-temperature treatment of the solid boronizing technique. The process is convenient to operate, the used equipment is simple, the obtained boronized layer is high in hardness, deep in thickness and good in wear resistance, and the service life of the nodular cast iron part is prolonged.
Drawings
FIG. 1 is a sectional view of a penetrated layer prepared in example 1 of the present invention;
FIG. 2 is a phase analysis diagram of a boriding layer of example 1 of the invention;
FIG. 3 is a wear curve of a boriding surface of the invention;
FIG. 4 is a graph of the wear rate of a boriding surface of the invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention relates to a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron, which is implemented by the following steps:
step 1, pretreating nodular cast iron;
the pretreatment in step 1 comprises:
step 1.1, sequentially using 600#, 800#, 1000# and 1200# metallographic abrasive paper to polish nodular cast iron, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
and step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in the step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion.
In the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 5-10 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 10-15 minutes by using absolute ethyl alcohol as a solvent.
When the phosphating solution for the nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 4-10% by mass of phosphoric acid, 5-15% by mass of nitrate, 3-8% by mass of zinc oxide, 2-10% by mass of citric acid, 1-5% by mass of a stabilizer and the balance of water, and the temperature is controlled to be 10-70 ℃ and the time is 5-30 minutes when the phosphating solution for the nodular cast iron is subjected to surface activation treatment.
Step 2, preparing a powder boronizing agent and a sealing material;
in the step 2, the powder boronizing agent is prepared by taking 3-10% of boron carbide, 5-10% of potassium fluoborate, 3-5% of activated carbon and 80-90% of silicon carbide as raw materials according to the mass backup ratio, uniformly mixing in a ball milling mode, then heating and drying, and then adding 1-2% of rare earth oxide according to the mass ratio.
In the step 2, the ball milling time is 6-20 hours, the ball milling rotating speed is 200-500 rpm, the boronizing agent is dried in a vacuum drying environment after ball milling, the drying time is controlled to be 60-120 minutes, and the temperature is controlled to be 120-150 ℃.
In the step 2, the sealing material is prepared by mixing 10-20% of water glass serving as a cementing material, 1-5% of sodium fluosilicate serving as a coagulant and 50-75% of clay serving as a base material in percentage by mass.
Step 3, boronizing treatment;
the step 3 is as follows:
3.1, performing pre-boronizing treatment on an iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and then cooling;
3.2, filling and mixing the boronizing agent prepared in the step 1 uniformly in a boronizing tank for completing pre-boronizing, burying the nodular cast iron sample pretreated in the step 1 in the boronizing agent, filling and compacting the boronizing agent in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
and 3.3, heating the sealed container to 200-400 ℃, preserving heat for 1-2 hours, removing water in the sealing material and the boronizing agent, then vacuumizing to 10-100 Pa, controlling the furnace temperature to 550-800 ℃, and controlling the boronizing time to 1-24 hours.
In step 3.2, a 15-20mm gap is kept between the sample and the box wall.
And 4, carrying out boronizing post-treatment to finally obtain a high-hardness boronized surface.
The step 4 is as follows:
step 4.1, roughly polishing to remove boronizing agent particles attached to the surface of a boronizing sample, and then finely polishing until the surface roughness Ra = 1.6-3.2 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 15-20 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.
Example 1
1. And sequentially using 600#, 800#, 1000# and 1200# sandpaper to polish the nodular cast iron sample, and removing a surface oxidation layer. Sequentially washing with absolute ethyl alcohol and acetone in an ultrasonic washing machine for 10 minutes, drying, and storing for later use.
2. Putting the sample into a phosphating solution for phosphating treatment, wherein the phosphating solution comprises the following components: 4% of phosphoric acid, 5% of nitrate, 3% of zinc oxide, 2% of citric acid, 1% of stabilizer and the balance of water; the phosphating time is 5 minutes, and the temperature is normal temperature. After the phosphating was completed, the sample was washed with water and dried.
3. The selected boronizing agent comprises the following components: 6% boron carbide (B) 4 C) 10% Potassium fluoroborate (KBF) 4 ) 83% silicon carbide (SiC), 1% lanthanum oxide (La) 2 O 3 ). Weighing the components according to the proportion, performing ball milling refinement on the boronizing agent in a ball milling mode, wherein the ball milling time is 10 hours, the ball milling rotation speed is 300rpm, and uniformly mixing.
4. And carrying out pre-boronizing treatment on the prepared container, filling a boronizing agent into the container, compacting and then sealing. Heating to 950 ℃ along with the furnace, preserving heat for 6 hours, and cooling along with the furnace.
5. Preparing a sealing material, taking 20% of water glass as a cementing material, 5% of sodium fluosilicate as an accelerant and 75% of clay as a base material, and fully stirring the materials for later use.
6. And (3) putting the phosphatized sample into a container, ensuring the thickness of the boronizing agent to be 20mm, and compacting. The prepared sealing material is used for sealing the end opening of the container, and the container is dried in the room temperature environment, so that the sealing effect is ensured.
7. And (3) putting the boronizing container into a resistance furnace, heating the boronizing container to 300 ℃ along with the furnace, preserving the heat for 2 hours, and evaporating the water in the container. Then, the furnace was turned to a vacuum furnace, and vacuum was applied to 10Pa to start heating. When the temperature is controlled to 550 to 900 ℃, the temperature is preferably 650 ℃. The boronizing time was controlled at 12 hours.
8. The furnace was cooled to room temperature and the container was removed from the furnace. And removing the sealing layer and taking out the sample. And (4) polishing and cleaning the boronizing agent attached to the surface of the sample by using No. 600 abrasive paper, and polishing the surface of the sample by using No. 1200 abrasive paper until the surface is smooth. Washing with absolute ethanol for 15 minutes in ultrasonic waves.
9. After boronizing, the boronized surface hardness was 1250HV measured using a microhardness tester 0.5 . XRD detection is carried out on the sample, the XRD spectrum is shown in figure 1, and the detection result shows that the sample surface infiltrated layer is made of FeB and Fe 2 B, the component B. When the cross section of the sample was examined by SEM analysis, the uniform thickness of the boriding layer was observed on the surface of the sample as shown in FIG. 2, and the average thickness was 60 μm.
Example 2
1. And sequentially using 600#, 800#, 1000# and 1200# sandpaper to polish the nodular cast iron sample, and removing a surface oxidation layer. Sequentially washing with absolute ethyl alcohol and acetone in an ultrasonic washing machine for 10 minutes, drying, and storing for later use.
2. Putting the sample into a phosphating solution for phosphating treatment, wherein the phosphating solution comprises the following components in percentage by weight: 3% of phosphoric acid, 5% of nitrate, 4% of zinc oxide, 2% of citric acid, 2% of a stabilizer and the balance of water; the phosphating time is 5 minutes, and the temperature is normal temperature. After the phosphating is finished, the sample is washed and dried.
3. The selected boronizing agent comprises the following components: 5% boron carbide (B) 4 C) 10% Potassium fluoroborate (KBF) 4 ) 83% silicon carbide (SiC), 2% cerium oxide (CeO) 2 ). Weighing the components according to the proportion, performing ball milling refinement on the boronizing agent in a ball milling mode, wherein the ball milling time is 6 hours, the ball milling rotation speed is 400rpm, and uniformly mixing.
4. And carrying out pre-boronizing treatment on the prepared container, filling a boronizing agent into the container, compacting and then sealing. Heating to 900 deg.c, maintaining for 8 hr and cooling.
5. Preparing a sealing material, taking 22% of water glass as a cementing material, 8% of sodium fluosilicate as a coagulant and 70% of clay as a base material, and fully stirring the materials for later use.
6. And (3) putting the phosphatized sample into a container, ensuring the thickness of the boronizing agent to be 20mm, and compacting. The prepared sealing material is used for sealing the port of the container, and the sealing effect is ensured by airing at room temperature.
7. And (3) putting the boronizing container into a resistance furnace, heating to 250 ℃ along with the furnace, preserving the heat for 4 hours, and evaporating the water in the container. Then transferred to a vacuum furnace, vacuumized to 50Pa and heated. The temperature is controlled at 600 ℃, and the boriding time is 24 hours.
8. The furnace was cooled to room temperature and the container was removed from the furnace. And removing the sealing layer and taking out the sample. And (3) polishing and cleaning the boronizing agent attached to the surface of the sample by using No. 600 abrasive paper, and polishing the sample to be smooth by using No. 1200 abrasive paper. The gel was washed with absolute ethanol for 15 minutes in an ultrasonic wave.
And (3) inspecting the wear performance of the boronized surface under the dry friction condition by adopting a multifunctional friction and wear tester. 304 stainless steel ball for loading sample, the diameter of the steel ball is 10mm, and the microhardness is 238HV 0.49 . The disk test pieces were the borided surfaces of the nodular cast iron matrix (QT 450), example 1 and example 2, and had a surface roughness of 0.1. Mu.m. Load 10N, speed 0.02m/s, time 180 minutes. The wear surface geometry is shown in figure 3. The results show that the wear curve of the ductile iron treated with low-temperature boriding is significantly lower than that of the untreated surface, with the wear depth of the surface of case 1 being only 3-5 μm. FIG. 4 shows the corresponding wear rates, which are 77.8% improvement in the boriding wear resistance of example 1 and 68.1% improvement in the boriding wear resistance of example 2. The test result shows that the ball prepared by the invention patentThe boriding surface of the graphite cast iron has good wear resistance.
Example 3
The invention relates to a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron, which is implemented by the following steps:
step 1, pretreating nodular cast iron;
the pretreatment in step 1 comprises:
1.1, sequentially polishing nodular cast iron by using metallographic abrasive paper of 600#, 800#, 1000# and 1200#, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
and step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in the step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion.
In the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 5 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 10 minutes by using absolute ethyl alcohol as a solvent.
When the phosphating solution for the nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 4% by mass of phosphoric acid, 5% by mass of nitrate, 3% by mass of zinc oxide, 2% by mass of citric acid, 1% by mass of a stabilizer and the balance of water, and the temperature is controlled to be 10 ℃ for 5 minutes when the phosphating solution for the nodular cast iron is subjected to surface activation treatment.
Step 2, preparing a powder boronizing agent and a sealing material;
in the step 2, the powder boronizing agent is prepared by taking 3% of boron carbide, 5% of potassium fluoborate, 3% of activated carbon and 80% of silicon carbide as raw materials in mass backup ratio, uniformly mixing by adopting a ball milling mode, heating and drying, and then adding 1% of rare earth oxide in mass ratio.
And 2, ball milling for 6 hours at the ball milling rotation speed of 200rpm, and drying the boronizing agent in a vacuum drying environment after ball milling, wherein the drying time is controlled to be 60 minutes, and the temperature is controlled to be 120 ℃.
In the step 2, the sealing material is prepared by blending 10% of water glass serving as a cementing material, 1% of sodium fluosilicate serving as a coagulant and 50% of clay serving as a base material.
Step 3, boronizing treatment;
the step 3 is specifically as follows:
step 3.1, performing pre-boronizing treatment on the iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and cooling;
3.2, filling and mixing the boriding medium prepared in the step 1 uniformly in a boriding tank which completes the pre-boriding, burying the nodular cast iron sample pretreated in the step 1 in the boriding medium, filling and compacting the boriding medium in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
and 3.3, heating the sealed container to 200 ℃, preserving heat for 1 hour, removing water in the sealing material and the boronizing agent, vacuumizing to 10Pa, and controlling the furnace temperature to 550 ℃ and the boronizing time to 1 hour.
In step 3.2, a 15mm gap is kept between the sample and the box wall.
And 4, carrying out boronizing post-treatment to finally obtain a boronized surface with high hardness.
The step 4 is specifically as follows:
4.1, roughly polishing to remove boriding agent particles attached to the surface of the boriding sample, and finely polishing to the surface roughness Ra =1.6 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 15 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.
Example 4
The invention relates to a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron, which is implemented by the following steps:
step 1, pretreating nodular cast iron;
the pretreatment in step 1 comprises:
step 1.1, sequentially using 600#, 800#, 1000# and 1200# metallographic abrasive paper to polish nodular cast iron, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
and step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in the step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion.
In the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 10 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 15 minutes by using absolute ethyl alcohol as a solvent.
When the phosphating solution for the nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 10 mass percent of phosphoric acid, 15 mass percent of nitrate, 8 mass percent of zinc oxide, 10 mass percent of citric acid, 1-5 mass percent of stabilizer and the balance of water, and the temperature is controlled to be 70 ℃ for 30 minutes when the phosphating solution for the nodular cast iron is subjected to surface activation treatment.
Step 2, preparing a powder boronizing agent and a sealing material;
in the step 2, the powder boronizing agent is prepared by taking 10% of boron carbide, 10% of potassium fluoborate, 5% of activated carbon and 90% of silicon carbide as raw materials in mass backup ratio, uniformly mixing by adopting a ball milling mode, heating and drying, and then adding 1-2% of rare earth oxide in mass ratio.
And 2, ball milling for 20 hours at the ball milling rotation speed of 500rpm, and drying the boronizing agent in a vacuum drying environment after ball milling, wherein the drying time is controlled to be 120 minutes, and the temperature is controlled to be 150 ℃.
In the step 2, the sealing material is prepared by mixing 20% of water glass serving as a cementing material, 5% of sodium fluosilicate serving as a coagulant and 75% of clay serving as a base material in percentage by mass.
Step 3, boronizing treatment;
the step 3 is as follows:
step 3.1, performing pre-boronizing treatment on the iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and cooling;
3.2, filling and mixing the boronizing agent prepared in the step 1 uniformly in a boronizing tank for completing pre-boronizing, burying the nodular cast iron sample pretreated in the step 1 in the boronizing agent, filling and compacting the boronizing agent in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
and 3.3, heating the sealed container to 400 ℃, preserving heat for 2 hours, removing moisture in the sealing material and the boronizing agent, vacuumizing to 100Pa, and controlling the furnace temperature to 800 ℃ and the boronizing time to 24 hours.
In step 3.2, a gap of 20mm is kept between the sample and the box wall.
And 4, carrying out boronizing post-treatment to finally obtain a boronized surface with high hardness.
The step 4 is specifically as follows:
step 4.1, roughly grinding to remove boronizing agent particles attached to the surface of a boronizing sample, and finely grinding until the surface roughness Ra =3.2 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 20 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.
Example 5
The invention relates to a preparation method of a low-temperature boronized wear-resistant surface of nodular cast iron, which is implemented by the following steps:
step 1, pretreating nodular cast iron;
the pretreatment in step 1 comprises:
step 1.1, sequentially using 600#, 800#, 1000# and 1200# metallographic abrasive paper to polish nodular cast iron, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
and step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in the step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion.
In the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 8 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 12 minutes by using absolute ethyl alcohol as a solvent.
When the phosphating solution for the nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 8% by mass of phosphoric acid, 10% by mass of nitrate, 3-8% by mass of zinc oxide, 7% by mass of citric acid, 3% by mass of a stabilizer and the balance of water, and the temperature is controlled to be 50 ℃ and the time is 20 minutes when the surface activation treatment is performed on the phosphating solution for the nodular cast iron.
Step 2, preparing a powder boronizing agent and a sealing material;
in the step 2, the powder boronizing agent is prepared by taking 6% of boron carbide, 6% of potassium fluoborate, 4% of activated carbon and 85% of silicon carbide as raw materials according to the mass backup ratio, uniformly mixing in a ball milling mode, heating and drying, and then adding 1.5% of rare earth oxide according to the mass ratio.
And 2, ball milling for 15 hours at the ball milling rotation speed of 400rpm, and drying the boronizing agent in a vacuum drying environment after ball milling, wherein the drying time is controlled to be 90 minutes, and the temperature is controlled to be 130 ℃.
In the step 2, the sealing material is prepared by blending 15% of water glass serving as a cementing material, 3% of sodium fluosilicate serving as a coagulant and 60% of clay serving as a base material.
Step 3, boronizing treatment;
the step 3 is as follows:
step 3.1, performing pre-boronizing treatment on the iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and cooling;
3.2, filling and mixing the boriding medium prepared in the step 1 uniformly in a boriding tank which completes the pre-boriding, burying the nodular cast iron sample pretreated in the step 1 in the boriding medium, filling and compacting the boriding medium in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
and 3.3, heating the sealed container to 300 ℃, preserving heat for 1.5 hours, removing water in the sealing material and the boronizing agent, then vacuumizing to 60Pa, and controlling the furnace temperature to 700 ℃ and the boronizing time to 13 hours.
In step 3.2, a gap of 18mm is kept between the sample and the box wall.
And 4, carrying out boronizing post-treatment to finally obtain a boronized surface with high hardness.
The step 4 is as follows:
step 4.1, roughly grinding to remove boronizing agent particles attached to the surface of a boronizing sample, and finely grinding until the surface roughness Ra =2 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 18 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.

Claims (1)

1. The preparation method of the low-temperature boronized wear-resistant surface of the nodular cast iron is characterized by comprising the following steps of:
step 1, pretreating nodular cast iron;
the pretreatment in the step 1 comprises the following steps:
1.1, sequentially polishing nodular cast iron by using metallographic abrasive paper of 600#, 800#, 1000# and 1200#, and removing a surface oxide layer;
step 1.2, carrying out ultrasonic cleaning twice on the nodular cast iron with the surface oxide layer removed in the step 1.1, and finally removing surface lipids and organic matters;
in the step 1.2, the first ultrasonic cleaning is ultrasonic cleaning for 5-10 minutes by using deionized water, and the second ultrasonic cleaning is ultrasonic cleaning for 10-15 minutes by using absolute ethyl alcohol as a solvent;
step 1.3, carrying out surface activation treatment on the nodular cast iron cleaned in step 1.2 by using phosphating solution to obtain an activated surface easy for boron atom diffusion;
when the phosphating solution for nodular cast iron is subjected to surface activation treatment in the step 1.3, the phosphating solution is prepared from 4-10% by mass of phosphoric acid, 5-15% by mass of nitrate, 3-8% by mass of zinc oxide, 2-10% by mass of citric acid, 1-5% by mass of a stabilizer and the balance of water, and the temperature is controlled to be 10-70 ℃ for 5-30 minutes when the phosphating solution for nodular cast iron is subjected to surface activation treatment;
step 2, preparing a powder boronizing agent and a sealing material;
the powder boronizing agent in the step 2 is prepared by taking 3-10% of boron carbide, 5-10% of potassium fluoborate, 3-5% of activated carbon and 80-90% of silicon carbide as raw materials in percentage by mass, uniformly mixing in a ball milling mode, heating and drying, and then adding 1-2% of rare earth oxide in percentage by mass;
in the step 2, the ball milling time is 6-20 hours, the ball milling rotating speed is 200-500 rpm, the boronizing agent is dried in a vacuum drying environment after ball milling, the drying time is controlled to be 60-120 minutes, and the temperature is controlled to be 120-150 ℃;
the sealing material in the step 2 is prepared by blending 10-20% of water glass serving as a cementing material, 1-5% of sodium fluosilicate serving as a coagulant and 50-75% of clay serving as a base material in percentage by mass;
and 3, boronizing treatment, wherein the step 3 is specifically as follows:
step 3.1, performing pre-boronizing treatment on the iron container to serve as a boronizing tank, namely filling the boronizing agent prepared in the step 2 into the iron container, compacting, sealing, heating to 950 ℃, preserving heat for 6 hours, and cooling;
3.2, filling and mixing the boriding medium prepared in the step 2 uniformly in a boriding tank which completes the pre-boriding, burying the nodular cast iron sample pretreated in the step 1 in the boriding medium, filling and compacting the boriding medium in the whole tank, and finally sealing by using the sealing material prepared in the step 2;
a 15-20mm gap is kept between the sample and the box wall in the step 3.2;
3.3, heating the sealed container to 200-400 ℃, preserving heat for 1-2 hours, removing water in the sealing material and the boronizing agent, then vacuumizing to 10-100 Pa, controlling the furnace temperature to 550-800 ℃, and controlling the boronizing time to 1-24 hours;
and 4, carrying out boronizing post-treatment to finally obtain a high-hardness boronized surface, wherein the step 4 is as follows:
step 4.1, roughly polishing to remove boronizing agent particles attached to the surface of a boronizing sample, and then finely polishing until the surface roughness Ra = 1.6-3.2 μm for later use;
and 4.2, ultrasonically cleaning the polished boronized sample for 15-20 minutes by using absolute ethyl alcohol, and drying to obtain a high-hardness boronized surface.
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