KR101614259B1 - Method for formation of hardened layer on martensitic precipitation-hardening stainless steel by the application of in-situ combination of aging treatment and plasma nitrocaburizing treatment - Google Patents

Method for formation of hardened layer on martensitic precipitation-hardening stainless steel by the application of in-situ combination of aging treatment and plasma nitrocaburizing treatment Download PDF

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KR101614259B1
KR101614259B1 KR1020150141923A KR20150141923A KR101614259B1 KR 101614259 B1 KR101614259 B1 KR 101614259B1 KR 1020150141923 A KR1020150141923 A KR 1020150141923A KR 20150141923 A KR20150141923 A KR 20150141923A KR 101614259 B1 KR101614259 B1 KR 101614259B1
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base material
treatment
stainless steel
plasma
sputtering
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이인섭
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동의대학교 산학협력단
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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
    • C23C8/06—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 gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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
    • 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
    • C23C8/06—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 gases
    • C23C8/08—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 gases only one element being applied
    • C23C8/24—Nitriding
    • 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
    • C23C8/06—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 gases
    • C23C8/08—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 gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Abstract

The present invention relates to a method for forming a surface hardened layer having excellent hardness and corrosion resistance on the surface of a martensitic precipitation hardening type stainless steel which has a problem in that corrosion resistance is lowered in nitriding treatment to increase the surface hardness, And a softening treatment are combined in situ . A method of forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material according to the present invention comprises the steps of aging treatment and softening treatment in -situ process, there is an effect of 1) improving the hardness of the base material itself, 2) securing the load supporting ability by securing a sufficient thickness of the surface hardening layer of the base material, 3) improving the corrosion resistance, and 4) improving the hardness of the surface of the base material.

Description

FIELD OF THE INVENTION The present invention relates to a method for forming a hardened layer on a surface of a martensitic precipitation hardening type stainless steel using a method in which an aging treatment and a softening treatment are combined in situ. -situ combination of aging treatment and plasma nitrocaburizing treatment}

The present invention relates to a method for forming a surface hardened layer having excellent hardness and corrosion resistance on the surface of a martensitic precipitation hardening type stainless steel which has a problem in that corrosion resistance is lowered in nitriding treatment to increase the surface hardness, And a method wherein the softening treatment is combined in-situ .

Stainless steel having a chromium content of at least 13 wt% or more in the metal material has a thin chromium oxide (Cr 2 O 3 ) film of 20-50 Å formed on the surface thereof to protect the surface from corrosion . Due to its high corrosion resistance, it is used in various fields such as foods, medicines and tableware. However, due to its low hardness characteristics, its use is limited to automobiles, machinery and electronic parts in high demand.

Therefore, surface treatment technology of stainless steel is being developed rapidly.

As a surface treatment method of stainless steel, carburizing method and nitriding method are generally used. First, the carburizing method is one of the oldest surface hardening methods. In the carburizing method, a base material having a low carbon content is heated at a temperature higher than 850 ° C in a state of contacting with a carbon-containing material such as charcoal and a gas containing carbon, To absorb carbon.

Since the nitriding process is performed at a low temperature, that is, in a ferrite region, as compared with other heat treatment curing methods, it is utilized in all industrial fields as a means for extending the life of mechanical parts. Nitriding refers to an operation of infiltrating nitrogen into the base material to harden the surface thereof.

Particularly, nitridation using a plasma is performed by infiltrating active ions by plasma discharge into a metal surface and curing treatment. In this state, while the metal material is installed in the reaction furnace, the reactor in a vacuum state is heated to a constant reaction temperature, And the surface of the metal material is hardened by a step of generating a plasma by applying a constant pulse negative voltage to the metal material.

In order to increase the abrasion resistance of the carbon steel, it is general to increase the hardness by diffusing and penetrating nitrogen from the surface of the metal material into the inside of the metal material at a temperature range of 500-600 占 폚 when the surface treatment is performed by the nitriding method.

However, if the nitriding treatment is applied to stainless steel, the surface hardness can be improved by forming a high hardened layer on the surface, but CrN is precipitated due to the nature of the nitriding process performed at 500 ° C or higher. The chromium content is reduced to 13 wt% or less around the precipitate, so that a thin and stable Cr 2 O 3 coating film can not be formed on the surface. Accordingly, there is a problem that the physical properties of the base material are lowered and the corrosion resistance is remarkably lowered. This is because the corrosion resistance is secured by lowering the nitriding process step to 450 DEG C or lower due to the poor corrosion resistance, but the inevitably effective abrasion resistance and the thin cured layer thickness It is impossible to secure the load supporting ability due to the load.

The austenitic stainless steel can secure some corrosion resistance when nitrided at a temperature of 450 DEG C or less, but ferritic and martensitic stainless steels still exhibit a drastically reduced corrosion resistance compared to untreated materials. This is because the austenitic stainless steel has an austenite structure which is an FCC crystal structure having high nitrogen and carbon solubility. The ferritic and martensitic stainless steels have a BCC crystal structure, so that voids in the crystal are relatively small in comparison with the FCC crystal structure, and thus they can not employ nitrogen and carbon. That is, nitrogen and carbon which are not solubilized in the lattice react with Cr to generate CrN and CrC, thereby lowering the chromium concentration around the precipitate. Therefore, if CrN and CrC are precipitated, a thin and stable Cr 2 O 3 coating film can not be formed, which causes deterioration of corrosion resistance.

The inventors of the present invention have been studying a method for solving corrosion resistance degradation which is a problem of the conventional low-temperature plasma nitriding process. When the aging treatment and the softening treatment are performed by an in-situ process, 1) ) Securing the load supporting ability by securing a sufficient thickness of the base material hardened layer, 3) improving the corrosion resistance, and 4) improving the hardness of the surface of the base material.

JP 2005-531694 A

An object of the present invention is to provide a method of forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material.

Another object of the present invention is to provide a martensitic precipitation hardening type stainless steel in which a supersaturated nitrided layer is formed as a hardened layer on the surface by the above method.

In order to achieve the above object,

The present invention provides a method of forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material comprising the following steps.

A pretreatment step (step S1) of pretreating the martensitic precipitation hardening type stainless steel base material and charging it into the chamber;

A first pre-sputtering process (step S2);

Aging step (step S3);

Performing a second pre-sputtering process (step S4);

A step of plasma softening treatment (step S5); And

Cooling step (S6).

The present invention also provides a martensitic precipitation hardening type stainless steel in which a supersaturated nitrided layer is formed as a hardened layer on the surface by the above method.

The method of forming a supersaturated nitrided layer as a hardened layer on the surface of the martensitic precipitation hardening type stainless steel base material according to the present invention is characterized in that 1) the hardness of the base material itself is improved, 2) securing the load supporting ability by securing a sufficient thickness of the surface hardened layer of the base material, 3) improving the corrosion resistance, and 4) improving the hardness of the surface of the base material.

1 is a flowchart of a method of forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material, which is characterized by treating an aging treatment and a softening treatment according to the present invention by an in-situ process.
2 is a photograph showing a surface cross-section of a base material prepared in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) according to the present invention.
3 is a graph showing the concentration distribution of N and C elements in the surface of a base material prepared in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) according to the present invention by Glow Discharge Optical Emission Spectroscopy As shown in FIG.
Fig. 4 is a graph showing the results of measurement of the element structure inside the surface of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention by X-ray diffractometer Fig. In FIG. 4, numerals (110) and (200) denote kinds of the martensite crystal plane as the base material.
5 is a graph showing the corrosion resistance of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention, And the results are shown in FIG.
Fig. 6 is a graph showing the results of measurement of the coercive force polarization of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) , And the surface was observed.
7 shows the surface hardness of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) (Supersaturated nitriding layer) thickness.
8 shows the hardness of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) according to the present invention Graph.
9 is a sectional hardness distribution diagram of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) depth profile).
10 is a schematic view of a plasma softening apparatus.
[Description of marks in Fig. 10]
H: Heater
P: Specimen (Stainless steel)
PS: Plasma
Vp: Vacuum pump
PC: Computer
1: chamber
2: substrate with cathode power
4:
5: Power supply

Hereinafter, the present invention will be described in detail.

The present invention provides a method of forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material comprising the following steps.

A pretreatment step (step S1) of pretreating the martensitic precipitation hardening type stainless steel base material and charging it into the chamber;

A first pre-sputtering process (step S2);

Aging step (step S3);

Performing a second pre-sputtering process (step S4);

A step of plasma softening treatment (step S5); And

Cooling step (S6).

Corresponding standards of the martensitic precipitation hardening type stainless steel include SUS 630, 17-4 PH, 15-5 PH, PH 13-8 Mo, Custom 450, Custom 455, Stainless W, Almar 362, IN-736, Croloy 16-6 PH, Corrax In the present invention, SUS630 is used as a base material.

In the method according to the present invention, the step S1 is a pre-treatment step of pre-treating the martensitic precipitation hardening type stainless steel base material and charging it into the chamber.

Specifically, a process for removing impurities on the surface of the base material includes a conventional cleaning process. First, in order to remove the oxide formed on the surface of the base material, it is immersed in a 5-35% nitric acid (HNO 3 ) solution at a temperature of 50-90 ° C for 1-60 minutes. After washing with alcohol, The surface of the base material was polished with a sandpaper, and the surface-ground base material was polished by alumina slurry (mirror-finished surface (polished surface)) using alumina slurry, followed by immersing in 10% caustic soda (NaOH) solution for 1-60 minutes, The surface of the base material is immersed again in alcohol and acetone solution, and the base material can be pretreated by ultrasonic cleaning.

Next, after the surface polishing and cleaning processes are completed, the base material is charged into a chamber constituted in a conventional plasma ion apparatus (see FIG. 10).

In the method according to the present invention, the step S2 is a step of performing a first pre-sputtering process. This first pre-sputtering treatment is to further remove impurities such as an oxide film on the surface of the base material by pre-sputtering the surface of the pre-treated base material.

Free sputtering is a process of ion bombardment of the surface of a base material, which is to bombard an inert element to remove metal molecules and impurities, and then to deposit a film on the surface to clean the surface. As the inert gas for performing the pre-sputtering, CO 2 , CO, Ar, and H 2 gases are generally used alone or in an appropriate mixture thereof.

Specifically, the pressure in the chamber is maintained at 5 × 10 -2 Torr or lower, power is supplied to the heater to raise the temperature in the chamber to the aging temperature of 200-800 ° C., and then the free sputtering gas (CO 2 , CO, Ar, H 2, etc. may be used alone or as a mixture, preferably, an Ar and H 2 mixed gas) is injected in an amount of 50-4,000 sccm to maintain a pressure of 0.1-5 Torr and a pressure of 200-1,000 V for a period of 20 to 60 minutes by plasma generation by applying a voltage to perform the first-order pre-sputtering. Here, the temperature in the chamber was matched with the aging temperature, which is the next step.

In the method according to the present invention, the step S3 is an aging step. This aging treatment serves to improve the hardness of the base material itself (see Experimental Example 7-8).

Specifically, after the pre-sputtering gas in step S2 is exhausted, the temperature is raised to 200-800 deg. C, preferably 300-500 deg. C, and then 50-4,000 sccm is selected from the group consisting of CO 2 , CO, Ar and H 2 One or more inert gases may be injected to maintain agitation for 2-6 hours, maintaining a pressure of 1-10 Torr, preferably 2-6 Torr. Here, as the inert gas, Ar or H 2 gas may be used alone, or a mixed gas thereof may be used.

In the method according to the present invention, the step S4 is a step of performing a second pre-sputtering process. The second free sputtering treatment removes impurities such as an oxide film that may be generated on the surface of the base material during the aging treatment and forms micro-defects on the surface of the base material so that nitrogen is diffused So that the supersaturated nitrided layer can be more stably formed.

Specifically, after the inert gas in step S3 is exhausted, a free sputtering gas (at least one gas selected from the group consisting of CO 2 , CO, Ar and H 2 , preferably a mixed gas of Ar and H 2 ) The chamber is maintained at a temperature of 300-500 ° C., preferably 350-450 ° C. and maintained at a pressure of 0.1-5 Torr and a plasma generated by applying a voltage of 200-1,000 V, Min for the second pre-sputtering. Here, the temperature in the chamber was matched with the next softening treatment temperature.

In the method according to the present invention, the step S5 is a step of plasma softening treatment. This plasma softening treatment is performed to form a supersaturated nitrided layer as a hardened layer on the surface of the base material to secure the surface hardness, corrosion resistance and sufficient thickness of the hardened layer to improve the load supporting ability.

Specifically, after discharging the pre-sputtering gas in step S4, a mixed gas composed of 55-95% H 2 , 1-20% CH 4 , and 5-45% N 2 in a volume ratio of 50-4,000 sccm And the plasma softening treatment can be performed by treating with plasma generation by applying a voltage of 1-10 Torr at 300-500 ° C and a voltage of 200-1,000 V for 5-25 hours.

The plasma softening treatment temperature may be 300-500 占 폚, preferably 350-450 占 폚, and more preferably 380-420 占 폚. If the softening treatment temperature is less than 300 ° C, a sufficient hardened layer thickness can not be ensured and the load supporting ability is lowered. If the softening treatment temperature is higher than 500 ° C, the corrosion resistance of the hardened layer is lowered have.

The mixed gas is preferably a mixed gas composed of 60-80% H 2 , 1-10% CH 4 , and 15-35% N 2 in a volume ratio.

In the method according to the present invention, the step S6 is a cooling step.

Specifically, the chamber may be cooled to 150-250 占 폚, preferably 180-220 占 폚, and then the base material on which the cured layer is formed may be taken out. If the temperature before the chamber is opened exceeds 250 ° C., there is a problem that the surface of the base material is oxidized.

The present invention also provides a martensitic precipitation hardening type stainless steel in which a supersaturated nitrided layer is formed as a hardened layer on the surface by the above method.

In the martensitic precipitation hardening type stainless steel in which a supersaturated nitrided layer is formed as a hardened layer on the surface by the method according to the present invention, CrN which deteriorates the corrosion resistance is not formed on the hardened layer formed on the surface, the corrosion resistance is remarkably improved (See Experimental Example 2), the thickness of the formed cured layer was sufficiently secured and the load supporting ability was excellent (see Experimental Example 5) (See Experimental Example 5), and the hardness of the base material itself was improved similarly to Comparative Example 2 in which the aging treatment alone was performed (see Experimental Example 6-7) ).

Therefore, in the method of forming the supersaturated nitriding layer as the hardened layer on the surface of the martensitic precipitation hardening type stainless steel base material according to the present invention, the aging treatment and the softening treatment are performed in the in-situ process, 2) securing the load supporting ability by securing a sufficient thickness of the base material hardened layer, 3) improving the corrosion resistance, and 4) improving the hardness of the surface of the base material.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

< Example  1> Martensitic system Precipitation hardening type  Curing layer formation of stainless steel

The apparatus for forming a cured layer in the first embodiment uses a conventional plasma softening apparatus, and a schematic diagram thereof is shown in FIG.

10, the plasma softening treatment softens the test piece P by passing a gas for nitriding and carburizing to the plasma generated outside the test piece P of the base material, And a heater (H) is installed inside the chamber (2). The test piece (P) is placed on the substrate (2). A gas injection part 4 is provided above the chamber 1 and a vacuum pump Vp is installed below the chamber 1 to generate a plasma PS around the specimen P. [ In addition, the substrate 2 and the heater H are configured to be supplied with power through a power supply device 5. The gas corresponding to the carburizing and nitriding process is introduced into the chamber 1 and the heater H is operated to increase the internal temperature and then the plasma PS is generated for a predetermined time to form the surface of the specimen P, .

Step S1: Of base metal  As a pre-treatment step Martensitic system Precipitation hardening type  Stainless steel base material is pretreated and charged into the chamber

SUS630 steel (martensitic precipitation hardening type stainless steel) was pre-treated as a base material and charged into a chamber.

Specifically, a process for removing impurities on the surface of the base material includes a conventional cleaning process. First, in order to remove the oxide formed on the surface of the base material, it was immersed in a 20% nitric acid (HNO 3 ) solution at a temperature of 70 ° C for 5 to 10 minutes. After washing with alcohol, it was immersed in 5% caustic soda (NaOH) solution for 5-10 minutes to remove organic matter such as oil. The surface of the base material was polished with sandpaper, and the surface-polished base material was subjected to mirror-surface treatment using alumina slurry to select the surface roughness. Further, the mirror-finished base material was immersed again in an alcohol and acetone solution, and the pre-treatment of the base material was completed by ultrasonic cleaning.

Step S2: Free sputtering (pre-sputtering) process step

In step S1, the pre-solidified base material is charged into the chamber, the pressure in the chamber is maintained at 5 x 10 &lt; -2 &gt; Torr or less by using a vacuum pump, power is supplied to the heater, ), A free sputtering gas (a mixed gas composed of 90% H 2 and 10% Ar) was injected in an amount of 100 sccm to maintain a pressure of 0.7 Torr and a plasma of 400 V The surface of the base material was subjected to free sputtering for 40 minutes during the production.

Step S3: Aging step

After the pre-sputtering gas in step S2 was exhausted, the temperature was maintained at 400 DEG C and an inert gas (Ar) of 200 sccm was injected, and the pressure was maintained at 4 Torr and aging was performed for 4 hours.

Step S4: Free sputtering (pre-sputtering) process step

After the inert gas in step S3 was exhausted, a gas for pre-sputtering (a mixed gas composed of 90% H 2 and 10% Ar) was injected in an amount of 100 sccm. The chamber was maintained at a temperature of 400 ° C. and maintained at a pressure of 0.7 Torr And the surface of the base material was subjected to free sputtering for 40 minutes by plasma generation by application of a voltage of 400V.

Step S5: plasma softening step

After the for-free sputtering gas in the step S4 the exhaust, injection of a mixed gas consisting of a volume ratio of 71% H 2, 4% CH 4, 25% N 2 into the chamber in an amount of 200 sccm, and at 400 ℃ 4 Torr Pressure holding and plasma generation by application of 400 V voltage for 15 hours to form a supersaturated nitrided layer on the surface of the base material.

Step S6: cooling step

The chamber was cooled to 200 DEG C, and then the base material on which the cured layer was formed was taken out.

< Comparative Example  1> SUS630 Lecture  Ready

Samples of the SUS630 steel (martensitic precipitation hardening type stainless steel) base material subjected to the solidification treatment were subjected to pretreatment in the same manner as in step S1 of Example 1,

< Comparative Example  2> Aged only SUS630 Lecture  Ready

The base material subjected to only the processes of steps S1-S3 and S6 in Example 1 was prepared as Comparative Example 2.

< Comparative Example  3> Only nitrided SUS630 Lecture  Ready

The base material subjected to only the processes of steps S1 and S4-S6 in Example 1 was prepared as Comparative Example 3. However, a mixed gas consisting of the volume ratio at the time of nitriding step S5 75% H 2, 25% N 2 , and was not added to 4% of the CH 4.

< Experimental Example  1> Base material  Evaluation of cross-section of surface hardened layer

Sectional photographs of the base material surface hardened layer obtained by using an optical microscope (manufacturer: Olympus, model name: BX51M) in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) The results are shown in Fig.

2 is a photograph showing a surface cross-section of a base material prepared in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) according to the present invention.

As shown in FIG. 2, in the cross-sectional photograph of the surface of the base material prepared in Comparative Example 3, which was treated by the conventional low temperature plasma ion nitriding process which was performed at 400 ° C., the supersaturated nitrided layer (α ' N ) had a thickness of about 16 μm, It can be seen that CrN in the form of black line is precipitated. On the other hand, the supersaturated nitrided layer formed on the surface of the base material prepared in Example 1 according to the present invention had a thickness of 15 쨉 m, and CrN did not precipitate and did not corrode even Vilella's reagent, which was a caustic solution. Respectively.

Therefore, CrN which deteriorates the corrosion resistance is not precipitated in the hardened layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention, so that the corrosion resistance is maintained.

< Experimental Example  2> Base material  Evaluation of hardened layer diffusion into the surface

In order to evaluate the degree of diffusion of the cured layer into the surface of the base material prepared in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) according to the present invention, Glow Discharge Optical Emission Spectroscopy Manufactured by Leco, model name: GDS850A). The results are shown in Fig.

3 is a graph showing the concentration distribution of N and C elements in the surface of a base material prepared in Example 1 (aging treatment + softening treatment) and Comparative Example 3 (nitriding treatment) according to the present invention by Glow Discharge Optical Emission Spectroscopy As shown in FIG.

As shown in FIG. 3, in the case of Comparative Example 3 (nitriding treatment), only nitrogen was diffused to about 16 μm from the surface. In the method of Example 1 according to the present invention, both nitrogen and carbon were simultaneously diffused, It was found that the nitrogen penetrated to about 15 μm and the carbon penetrated to about 20 μm. These results are in good agreement with the result of the microstructure of the surface of the base material of FIG. 2.

Therefore, the cured layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention has an effect of sufficiently spreading into the inside of the base material.

< Experimental Example  3> Evaluation of X-ray diffraction analysis result

In order to evaluate the internal element constitution of the surface of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention, an X-ray diffractometer Rigaku, model name: D / Max-200). The results are shown in FIG.

Fig. 4 is a graph showing the results of measurement of the element structure inside the surface of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention by X-ray diffractometer Fig. In FIG. 4, numerals (110) and (200) denote kinds of the martensite crystal plane as the base material.

As shown in FIG. 4, it can be seen that the base material is a martensite (α ') structure. In the conventional low temperature plasma ion nitriding method of Comparative Example 3, CrN and nitrogen expanded martensite (α' N ) . In the case of the specimen processed in Example 1 according to the present invention, CrN was hardly precipitated and the peak of the supersaturated nitriding layer was increased as compared with the specimen treated by the conventional low temperature plasma ion nitriding method of Comparative Example 3, (iron carbonitride) is has been found that ε-Fe 2 -3 (N, C) is formed in a very small amount.

Therefore, CrN which deteriorates the corrosion resistance is not precipitated in the hardened layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention, so that the corrosion resistance is maintained.

< Experimental Example  4> Evaluation of corrosion resistance

In order to evaluate the corrosion resistance of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention, a specimen was immersed in a 3.5% The above was measured with a Polarization Analyzer (manufacturer: Princeton Applied Research, model name: VersaSTAT3), and the results are shown in FIG.

5 is a graph showing the corrosion resistance of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) according to the present invention, And the polarization is measured.

As shown in FIG. 5, the treatment method of Example 1 according to the present invention has higher corrosion potential and lower corrosion current density than the untreated raw material of Comparative Example 1 and the conventional low temperature plasma ion nitriding treatment of Comparative Example 3, .

In addition, after the above-mentioned analysis of the electromotive force polarization, the surface of the base material of Example 1, Comparative Example 1 and Comparative Example 3 was observed to examine the degree of corrosion, and the results are shown in FIG.

Fig. 6 is a graph showing the results of measurement of the coercive force polarization of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated) and Comparative Example 3 (nitriding treatment) , And a microscope (manufactured by OlymPus, model name: SZ61).

As shown in Fig. 6, the mark of the circular shape seen in the untreated material of Comparative Example 1 was generated due to severe pitting corrosion. The formula is a local corrosion that is a common form of corrosion in stainless steel and this corrosion is a major cause of the material becoming very fragile due to stress concentration at the locally damaged part. On the other hand, it can be seen from the photograph of the surface of the sample of the result of the treatment according to the first embodiment of the present invention that the circular mark does not appear, which indicates that the stress concentration phenomenon can not occur. On the other hand, the surface photograph of the specimen by the conventional low-temperature plasma nitriding treatment of Comparative Example 3 alone shows that the minute marks of the minute round shape are generated more than those of the untreated material of Comparative Example 1. [ The reason for this is that as shown in the results of FIG. 5, the corrosion resistance of the specimen of Comparative Example 3 is the lowest, and the corrosion current density is the highest, so that the corrosion proceeds very quickly. Therefore, the conventional low-temperature plasma nitriding treatment of Comparative Example 3 alone exhibited a corrosion resistance and a high corrosion resistance and no advantage of stainless steel.

Therefore, the cured layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention has an effect of significantly improving the corrosion resistance.

< Experimental Example  5> Surface hardness and hardening layer (supersaturation Nitride layer ) Thickness evaluation

The surface hardness and the thickness of the hardened layer of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) And the results are shown in Fig.

Specifically, the surface hardness was measured using a micro Vickers hardness tester (manufacturer: Matsuzawa, model: MMT-X7B) and the thickness of the cured layer was measured by Glow Discharge Optical Emission Spectroscopy (Leco, model: GDS850A ).

7 shows the surface hardness of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) (Supersaturated nitriding layer) thickness.

As shown in FIG. 7, the surface hardness of the specimen treated by the method of Example 1 according to the present invention was at least 3 times higher than that of Comparative Example 1 (untreated material) and Comparative Example 2 (aged treated specimen) And the thickness of the supersaturated nitriding layer was about 4 μm (GDOS standard) thicker than that of Comparative Example 3 (nitriding treatment).

Therefore, the cured layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention is not only excellent in surface hardness, but also has a sufficient thickness of the hardened layer and excellent in load supporting ability.

< Experimental Example  6> Base material  Own  Hardness  evaluation

The hardness of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) according to the present invention was evaluated, Is shown in Fig.

Specifically, the hardness of the base material itself was measured using a micro Vickers hardness tester (manufacturer: Matsuzawa, model: MMT-X7B).

8 shows the hardness of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) according to the present invention Fig.

As shown in Fig. 8, the bulk hardness of the base material itself of the test piece treated by the method of Example 1 (aging treatment + softening treatment) according to the present invention was higher than that of the test piece of Comparative Example 2 (aging treatment) 3 (nitridation treatment) hardness of the specimen.

Therefore, the cured layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention not only has excellent surface hardness, but also has the effect of simultaneously increasing the hardness of the base material itself by aging treatment.

< Experimental Example  7> Base material  Evaluation of hardness from surface to depth

The hardness according to the depth was evaluated from the surface of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) according to the present invention , And the results are shown in Fig.

Specifically, the hardness along the depth from the surface of the base material was measured using a micro Vickers hardness tester (manufacturer: Matsuzawa, model: MMT-X7B).

9 is a sectional hardness distribution diagram of the base material prepared in Example 1 (aging treatment + softening treatment), Comparative Example 1 (untreated), Comparative Example 2 (aging treatment) and Comparative Example 3 (nitriding treatment) depth profile).

9, the section hardness of the specimen treated by the method of Example 1 (aging treatment + softening treatment) according to the present invention was compared with the section hardness of the specimen treated by the method of Comparative Example 3 (nitriding treatment) And the hardness was high in all sections. It was found that the hardness of the specimen treated by the method of Comparative Example 2 (aged treatment) was almost the same from the point of about 40 μm from the surface of the base material.

Therefore, it has been confirmed that the cured layer formed on the surface of the martensitic precipitation hardening type stainless steel by the method according to the present invention not only has excellent surface hardness, but also has the effect of simultaneously increasing the hardness of the base material by aging treatment.

Claims (11)

A method for forming a supersaturated nitrided layer as a hardened layer on the surface of a martensitic precipitation hardening type stainless steel base material comprising the steps of:
A pretreatment step (step S1) of pretreating the martensitic precipitation hardening type stainless steel base material and charging it into the chamber;
A step of performing a first pre-sputtering treatment to remove impurities on the surface of the base material (step S2);
Aging step (step S3);
A second pre-sputtering process is performed to remove impurities on the surface of the base material and to form micro-defects on the surface of the base material (step S4);
A step of nitrocaburizing the plasma (step S5); And
Cooling step (S6).
The method according to claim 1,
The pretreatment in step S1 is performed by immersing the substrate in a 5-35% nitric acid (HNO 3 ) solution at a temperature of 50-90 ° C for 1-60 minutes to remove oxides formed on the surface of the base material, washing with alcohol, The surface of the base material is polished by sandpaper, and the surface-polished base material is polished by using an alumina slurry (manufactured by Nippon Aerospace Industries Co., Ltd.) for 1 to 60 minutes in 1-10% caustic soda (NaOH) Characterized in that after the mirror surface treatment is performed to select the roughness of the surface, the mirror-finished base material is again immersed in alcohol and acetone solution, and the preform is pretreated by ultrasonic cleaning.
The method according to claim 1,
In the first pre-sputtering in step S2, the pressure in the chamber is maintained at 5 × 10 -2 Torr or lower, power is supplied to the heater, and the temperature in the chamber is adjusted to the aging temperature of 200-800 And then at least one kind of free sputtering gas selected from the group consisting of CO 2 , CO, Ar and H 2 is injected in an amount of 50-4,000 sccm to maintain a pressure of 0.1-5 Torr and a pressure of 200-1,000 V for a period of 20 to 60 minutes by plasma generation by application of a voltage.
The method according to claim 1,
The pre-sputtering gas of step S2 is exhausted, and after the exhaust gas is heated to 300-500 DEG C, the aging treatment of step S3 is followed by at least one inert gas selected from the group consisting of CO 2 , CO, Ar and H 2 at 50-4,000 sccm Gas is injected, the pressure is maintained at 2-6 Torr, and the treatment is carried out for 2-6 hours.
The method according to claim 1,
The second pre-sputtering in the step S4 is performed by discharging at least one kind of free sputtering gas selected from the group consisting of CO 2 , CO, Ar and H 2 to 50-4,000 sccm, wherein the chamber is maintained at a temperature of 300-500 DEG C and maintained at a pressure of 0.1-5 Torr and a plasma generation by application of a voltage of 200-1000 V for 20-60 minutes. .
The method according to claim 1,
Plasma softening process at the step S5 is a mixed gas consisting of the volume ratio and then the gas for the pre-sputtering of said exhaust step S4, 55-95% H 2, 1-20% in a chamber CH 4, 5-45% N 2 Is injected in an amount of 50 to 4,000 sccm, and the treatment is carried out for 5 to 25 hours by plasma generation by applying a pressure of 1 to 10 Torr and a voltage of 200 to 1,000 V at 300 to 500 캜.
The method according to claim 6,
Wherein the temperature of the plasma softening treatment is 350-450 占 폚.
8. The method of claim 7,
Wherein the temperature of the plasma softening treatment is 380 - 420 占 폚.
The method according to claim 1,
Wherein the cooling in step S6 is performed by cooling the chamber to 150-250 占 폚 and then removing the base material from which the cured layer has been formed.
The method according to claim 1,
Corresponding standards of the martensitic precipitation hardening type stainless steel are SUS 630, 17-4 PH, 15-5 PH, PH 13-8 Mo, Custom 450, Custom 455, Stainless W, Almar 362, IN-736, Croloy 16-6 PH and Corrax &Lt; / RTI &gt;
A martensitic precipitation hardening type stainless steel which is treated by the method of claim 1 and has a superposed nitrided layer formed as a hardened layer on its surface.
KR1020150141923A 2015-10-12 2015-10-12 Method for formation of hardened layer on martensitic precipitation-hardening stainless steel by the application of in-situ combination of aging treatment and plasma nitrocaburizing treatment KR101614259B1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109487061A (en) * 2019-01-10 2019-03-19 成都先进金属材料产业技术研究院有限公司 The heat treatment method of martensitic precipitation 06Cr15Ni5Cu2Ti
KR102330937B1 (en) * 2020-05-22 2021-11-24 동의대학교 산학협력단 Method for manufacturing martensitic precipitation hardening stainless steel for improving corrosion resistance and surface hardness and method for surface treatment of cable protector

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005534808A (en) * 2002-07-29 2005-11-17 コーニンクレッカ　フィリップス　エレクトロニクス　エヌ　ヴィ Plasma nitriding of maraging steel, shaver cap and cutting device for electric shaver manufactured from such maraging steel, and electric shaver

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005534808A (en) * 2002-07-29 2005-11-17 コーニンクレッカ　フィリップス　エレクトロニクス　エヌ　ヴィ Plasma nitriding of maraging steel, shaver cap and cutting device for electric shaver manufactured from such maraging steel, and electric shaver

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109487061A (en) * 2019-01-10 2019-03-19 成都先进金属材料产业技术研究院有限公司 The heat treatment method of martensitic precipitation 06Cr15Ni5Cu2Ti
CN109487061B (en) * 2019-01-10 2020-07-07 成都先进金属材料产业技术研究院有限公司 Heat treatment method of martensite precipitation hardening stainless steel 06Cr15Ni5Cu2Ti
KR102330937B1 (en) * 2020-05-22 2021-11-24 동의대학교 산학협력단 Method for manufacturing martensitic precipitation hardening stainless steel for improving corrosion resistance and surface hardness and method for surface treatment of cable protector

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