WO2014104085A1 - 表層を硬化させた金属材及びその表層硬化処理方法 - Google Patents
表層を硬化させた金属材及びその表層硬化処理方法 Download PDFInfo
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- WO2014104085A1 WO2014104085A1 PCT/JP2013/084642 JP2013084642W WO2014104085A1 WO 2014104085 A1 WO2014104085 A1 WO 2014104085A1 JP 2013084642 W JP2013084642 W JP 2013084642W WO 2014104085 A1 WO2014104085 A1 WO 2014104085A1
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- nitrogen
- metal material
- nitriding
- surface layer
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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
- C23C8/02—Pretreatment of the material to be coated
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- 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
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- 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
- C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
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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
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
- Y10T428/24983—Hardness
Definitions
- the present invention relates to a metal material obtained by curing a surface layer and a surface layer curing method.
- a method of forming a nitrogen diffusion layer on a surface layer of a metal material and curing the surface layer is known, and is called a nitriding treatment.
- a nitriding treatment method capable of forming a nitrogen diffusion layer on the surface layer of a metal material at a lower temperature there is a plasma nitriding treatment using nitrogen plasma.
- ion nitriding treatment since nitrogen ions in the nitrogen plasma are excessively supplied to the surface of the metal material, only the nitrogen diffusion layer is formed on the surface layer of the metal material.
- Patent Document 1 there is a problem that a brittle nitrogen compound layer is formed (see Patent Document 1 below).
- the present invention has been made in view of the above-described conventional circumstances, and is a metal obtained by curing a surface layer by forming a nitrogen diffusion layer deeper without forming a nitrogen compound layer on the surface layer of the metal material.
- the object is to provide a material and a method for curing the surface layer thereof.
- the metal material obtained by curing the surface layer of the first invention is A metal material whose surface layer is hardened by nitriding the base material, No nitrogen compound layer is formed on the surface layer of the base material, And the Vickers hardness to the depth of 78 micrometers from the surface of the said base material is 5% or more higher than the said base material, It is characterized by the above-mentioned.
- This metal material does not form a brittle nitrogen compound layer on the surface layer, and a metal material in which the Vickers hardness up to a depth of 78 ⁇ m from the surface is increased by 5% or more compared to the base material by nitriding treatment. Therefore, a hard metal material having high wear resistance can be obtained without removing the nitrogen compound layer by nitriding after polishing.
- the surface layer curing method of the second invention is A pretreatment step by shot blasting that causes the elastic body to collide with the surface of the metal material;
- the pretreated metal material that has undergone the pretreatment step is placed in a treatment tank, and the surface of the metal material is formed by nitrogen plasma generated by irradiating an electron beam to nitrogen gas introduced into the treatment tank.
- a nitriding step for forming a nitrogen diffusion layer is
- a nitriding treatment is performed in which a nitrogen diffusion layer is formed on a surface layer of a pretreated metal material by nitrogen plasma after a pretreatment step of performing a shot blasting process in which an elastic body collides with the surface of the metal material.
- the nitrogen diffusion layer can be formed deeper and the surface layer of the metal material can be cured.
- the change in hardness of the surface layer can be continuously changed. In this case, the hardened surface layer is unlikely to break due to stress concentration or fatigue.
- the nitrogen ions are prevented from entering the surface of the pretreated metal material, and only nitrogen atoms are incident on the surface.
- the nitrogen diffusion layer can be formed on the surface layer. In this case, since nitrogen ions can be prevented from entering the surface of the pretreated metal material, surface deposition of the nitrogen compound layer due to excessive supply of nitrogen ions can be suppressed.
- the nitriding treatment step is provided with a shielding member surrounding the pretreated metal material, and by this shielding member, the surface of the pretreated metal material of the nitrogen ions is provided. Can be blocked. In this case, it is possible to easily shield nitrogen ions from entering the surface of the pretreated metal material by using the shielding member.
- sample (metal material) 40 for hardening the surface layer As a sample (metal material) 40 for hardening the surface layer, tool steel SKD61 used for metals and tools was used.
- the sample 40 has a disk shape, a diameter of 20 mm, and a thickness of 2 mm.
- the surface layer curing method includes a pretreatment step of performing a shot blasting process in which a shot material (elastic body) 2 collides with the surface of the sample 40, and nitrogen is applied to the surface layer of the sample 40 that has been pretreated with a nitrogen plasma in the plasma nitriding apparatus 9. It consists of two steps, a nitriding treatment step for forming the diffusion layer 40D.
- the blasting apparatus 1 is a mechanical shot blasting apparatus SMAP (manufactured by Toyo Abrasive Co., Ltd.).
- the blasting device 1 includes a projection unit 3 that projects the shot material 2 while rotating, an injection nozzle 4 having a nozzle diameter of 5 mm, and a cabinet unit 5 that guides the shot material 2 to the injection nozzle 4.
- the angle between the sample 40 and the injection nozzle 4 is 40 °, and the distance from the tip of the injection nozzle 4 to the sample 40 is 40 mm.
- Fig. 2 shows a schematic diagram of the shot material 2.
- the shot material 2 is a resin sphere 6 having a diameter of 0.4 mm, and the entire circumference thereof is covered with diamond abrasive grains 7 having a particle diameter of 1 ⁇ m or less. Since the inside of the shot material 2 is made of resin, it has elasticity. The mass of the shot material 2 is about 4.55 ⁇ 1E-8 kg.
- the shot material 2 is projected from the projection unit 3 of the blasting device 1 that rotates at a rotational speed of 1 Hz.
- the shot material 2 projected from the projection unit 3 passes through the cabinet unit 5 and is sprayed onto the sample 40 from the spray nozzle 4 formed narrower than the cabinet unit 5. Then, the shot material 2 that maintains the kinetic energy when projected from the projection unit 3 collides with the sample 40. This collision energy is about 7.1 ⁇ 1E-9J.
- the injection time of the shot material 2 is 1 minute, and the injection amount of the shot material is 500 g.
- the shot blasting process in which the shot material 2 having elasticity collides with the surface of the sample 40 has a much lower collision energy than the shot blasting process using a conventional metal particle (steel shot). For this reason, only a low value of the surface hardening of the sample 40 after the shot blast treatment is observed as compared with the steel shot. That is, the hardness of the sample 40 after the shot blasting is 100 Hv or less in terms of Vickers hardness.
- the plasma nitriding apparatus 9 used in the nitriding process includes an electron beam gun 10 and a processing tank 20 as shown in FIG.
- the electron beam gun 10 has a discharge region 11 and an acceleration region 12.
- the discharge region 11 is partitioned into a first discharge region 11A and a second discharge region 11B by an intermediate electrode S1 having a small hole in the center.
- the first discharge region 11A houses the filament 13 and the cathode S0.
- the first discharge region 11A communicates with a first gas pipe 14 communicated with an argon gas supply source.
- the first gas pipe 14 is provided with a first mass flow controller 14A.
- the first gas pipe 14 is provided with an on-off valve 14B on the upstream side and the downstream side of the first mass flow controller 14A.
- the second discharge region 11B is separated from the acceleration region 12 by the discharge anode S2.
- the acceleration region 12 is formed between the discharge anode S2 and the acceleration electrode SA to which the acceleration voltage Va is applied to the discharge anode S2.
- the electron beam gun 10 configured in this manner starts discharge by introducing argon gas from the first gas pipe 14 into the discharge region 11 and applying a DC voltage between the cathode S0 and the intermediate electrode S1. Then, argon is ionized and a large amount of electrons are generated in the discharge region 11. Only electrons are accelerated from the plasma space by the acceleration voltage Va between the discharge anode S2 and the acceleration electrode SA to generate an electron beam. The generated electron beam is irradiated into the processing tank 20.
- the processing tank 20 forms a plasma region 21.
- the plasma region 21 communicates with a second gas pipe 22 that communicates with a nitrogen gas supply source.
- the second gas pipe 22 is provided with a second mass flow controller 22A.
- the second gas pipe 22 is provided with an on-off valve 22B on the upstream side and the downstream side of the second mass flow controller 22A.
- the plasma region 21 communicates with a vacuum pump 23 for depressurization via a gate valve 24.
- the treatment tank 20 is provided with an electric heater 25 around the intermediate portion.
- Nitrogen gas is introduced from the second gas pipe 22 into the plasma region 21 and irradiated with an electron beam from the electron beam gun 10, whereby nitrogen molecules are dissociated and ionized to generate nitrogen plasma in the treatment tank 20.
- the plasma nitriding apparatus 9 is provided with a quartz sample stage 26 in the plasma region 21. Further, the plasma nitriding apparatus 9 includes a metal mesh cage (shielding member) 30 that is mounted on the sample stage 26 and is electrically insulated from the processing tank 20.
- the cage 30 is formed of a stainless steel wire mesh 31 in a columnar shape, and a stainless steel ring-shaped frame 32 is attached to both ends thereof.
- the cage 30 is provided with a circular wire mesh 31 at both ends formed by a frame 32.
- the metal mesh 31 is made of a wire rod having a diameter of 0.16 mm and is knitted in a mesh shape at intervals of 40 meshes per inch.
- the cage 30 can be arranged with a sample 40 that has been pretreated.
- the plasma nitriding apparatus 9 includes a first DC power supply 41 that can apply a positive potential bias voltage higher than the plasma potential at the position where the sample 40 is disposed to the sample 40.
- the plasma nitriding apparatus 9 includes a second DC power supply 31 that can apply a negative bias voltage to the cage 30. Further, the plasma nitriding apparatus 9 includes a thermocouple 42 that can measure the temperature of the workpiece 40.
- the second DC power supply 31 applies a negative bias voltage to the cage 30.
- nitrogen ions in the nitrogen plasma are accelerated toward the cage 30.
- the metal mesh 31 constituting the cage 30 has a mesh shape, the nitrogen ions that have reached the cage 30 pass through the mesh.
- a part of the nitrogen ions incident on the wire constituting the wire mesh 31 receives electrons from the wire to become nitrogen atoms, and is incident on the surface of the sample 40 while maintaining its acceleration. That is, only nitrogen atoms are incident on the surface of the sample 40.
- a positive bias voltage higher than the plasma potential is applied to the sample 40 by the first DC power supply 41. For this reason, the nitrogen ions that have entered the cage 30 are rebounded by the electric field of the sample 40 and are blocked from entering the surface of the sample 40. In this way, a method in which only nitrogen atoms of nitrogen plasma are selectively incident on the surface of the sample 40 to form the nitrogen diffusion layer 40D on the surface layer of the sample 40 is referred to as “neutral nitriding”.
- the argon gas flow rate is controlled to 20 sccm using the first mass flow controller 14A. Further, the flow rate of nitrogen gas is controlled to 40 sccm using the second mass flow controller 22A.
- the acceleration voltage Va was 80 V, and the beam current of the electron beam was 8.0 A.
- the nitrogen pressure in the treatment tank 20 was 0.4 Pa, the electric heater 25 was heated, and the temperature of the sample 40 was 500 ° C. Under the above conditions, the surface of the sample 40 was subjected to neutral nitridation treatment or ion nitridation treatment.
- samples N1, N2, and N3 were prepared in which neutral nitriding treatment was performed at three levels of treatment time of 3, 6, and 12 hours.
- Samples I1, I2, and I3 performed over time were prepared. And about all the samples 40, the cross-sectional observation by the metal microscope and the Vickers hardness evaluation of the depth direction were performed.
- the procedure for observing the cross section of the sample 40 with a metal microscope is as follows. First, the treated sample 40 is cut with a diamond cutter and embedded in a resin, and then the cross section is polished with alumina having a particle size of 0.05 ⁇ m. Then, only the nitrogen diffusion layer 40D was changed to black by being immersed in a nital solution having a nitric acid concentration of 3% for 30 seconds.
- FIG. 4 (a) shows a cross-sectional metal micrograph of sample N ′ obtained by performing only the neutral nitriding for 6 hours without performing pretreatment
- FIG. 4 (b) shows the sample N2 obtained by performing the pretreatment and neutral nitriding treatment for 6 hours.
- a cross-sectional metal micrograph is shown.
- the region that is changed to black in FIG. 4 corresponds to the nitrogen diffusion layer 40D.
- the sample N2 subjected to the pretreatment and the neutral nitriding treatment has a layer discolored in black, and the nitrogen diffusion layer 40D is formed deeper than the sample N ′ subjected to only the neutral nitriding. I understand that. Therefore, it can be seen that the nitrogen diffusion layer 40D can be formed deeper on the surface of the sample 40 by performing the subsequent plasma nitriding process than when the preprocessing is not performed.
- FIGS. 5 (a), (b), and (c) show cross-sectional metal micrographs of samples N1 to N3 that were pre-treated and neutral-nitrided for 3, 6, and 12 hours, respectively.
- FIG. 6 is a graph showing the processing time dependence of the depth profile of Vickers hardness of samples N1 to N3 subjected to pretreatment and neutral nitriding treatment.
- FIGS. 7A, 7B, and 7C show cross-sectional metal micrographs of Samples I1 to I3 that have been subjected to ion nitriding for 1.5, 3, and 6 hours, respectively.
- FIG. 8 is a graph showing the processing time dependence of the depth profile of Vickers hardness of samples I1 to I3 subjected to ion nitriding.
- the samples N1 to N3 subjected to the ion nitriding treatment and the neutral nitriding treatment increase the treatment time, so that the black-discolored layer spreads. Therefore, by increasing the treatment time, nitrogen can be obtained. It can be seen that the diffusion layer 40D is formed deeper. Further, in any sample 40 subjected to neutral nitriding treatment and ion nitriding treatment from FIGS. 6 and 8, the Vickers hardness of the surface layer of sample 40 is increased by increasing the treatment time, and the surface layer hardening is promoted. I understand.
- the Vickers hardness of the SKD61 sample 40 before nitriding is about 630 Hv.
- the depth at which the Vickers hardness is 5% higher (about 660 Hv) than the sample 40 before nitriding is defined as “nitrogen diffusion depth”.
- the nitrogen diffusion depths of the three samples (samples N1 to N3) subjected to the neutral nitriding treatment are estimated to be about 45 ⁇ m, about 67 ⁇ m, and about 92 ⁇ m, respectively.
- the nitrogen diffusion depths of the three samples (samples I1 to I3) subjected to ion nitriding are estimated to be about 48 ⁇ m, about 80 ⁇ m, and about 128 ⁇ m, respectively.
- the nitrogen diffusion depth becomes deeper by increasing the processing time for any of the samples 40 subjected to the neutral nitriding treatment and the ion nitriding treatment. Further, it can be seen that the sample 40 subjected to the ion nitriding treatment has a faster formation rate of the nitrogen diffusion layer 40D and the nitrogen diffusion depth deeper than the sample 40 subjected to the neutral nitriding treatment.
- a white nitrogen compound layer 40C is confirmed on the surface of all the samples I1 to I3 subjected to the ion nitriding treatment. Further, focusing attention on FIG. 5, the nitrogen compound layer 40C is not visually confirmed in the samples N1 to N3 subjected to the neutral nitriding treatment.
- FIG. 9 shows the relationship between the surface nitrogen concentration and the surface precipitate material with respect to the treatment time.
- FIG. 9 shows that when the nitrogen concentration in the SKD 61 exceeds 6 wt% (generation threshold), the nitrogen compound layer ⁇ (40C) of the elements contained in the SKD 61 is deposited on the surface.
- the processing time is about several tens of minutes and the generation threshold is exceeded.
- the curve of the surface nitrogen concentration with respect to the treatment time is gentle, and the nitrogen compound layer ⁇ (40C) does not precipitate on the surface unless the nitriding treatment is performed for 9 hours or more.
- the formation rate of the nitrogen diffusion layer 40D is higher in the ion nitriding process than in the neutral nitriding process, but it is impossible in principle to form the nitrogen diffusion layer 40D deeply without forming the nitrogen compound layer 40C on the surface. It is.
- generation threshold value is exceeded, Therefore The thin nitrogen compound layer 40C of the grade which cannot be confirmed from the cross-sectional metal micrograph of FIG.5 (c) is formed in the surface of the sample 40 It is speculated that it is.
- a shot blasting process is performed in which the shot material 2 having elasticity collides with the surface of the sample 40, and then In addition, the neutral nitriding treatment may be performed for 9 hours.
- the nitrogen diffusion depth at the neutral nitriding time of 9 hours is determined to be about 78 ⁇ m by linearly approximating the data of the samples N1 to N3 subjected to neutral nitriding. Can do.
- the neutral nitriding in which only nitrogen atoms contribute to the formation of the nitrogen diffusion layer 40D after the shot blasting process in which the shot material 2 having elasticity collides with the surface of the metal material 40 is performed as a pretreatment.
- the metal material 40 having a high hardness from the surface to a depth of about 78 ⁇ m can be produced without depositing the nitrogen compound layer 40C on the surface layer of the metal material 40.
- the metal material 40 that has been subjected to the nitriding treatment is excellent in wear resistance, and can be used for a tool or the like so that the service life can be extended. Further, since the brittle nitrogen compound layer 40C is not formed on the surface layer of the metal material 40, it is not necessary to remove it by polishing or the like, and the operation cost can be reduced.
- the metal material 40 when performing a composite curing process for coating the metal material 40 with a TiN (titanium nitride) film or the like, if the nitrogen compound layer 40C is formed on the surface layer, the coated TiN film may be peeled off. is there.
- the metal material 40 that has been subjected to the neutral nitriding treatment is also effective when performing the composite curing treatment because the nitrogen compound layer 40C is not formed on the surface layer of the metal material 40.
- the hardness change rate from the surface to about 50 ⁇ m is ⁇ 206/40 [0.01 Hv / ⁇ m], that is, ⁇ 5.1 [0.01 Hv / ⁇ m] in the treatment for 12 hours. ⁇ m].
- the hardness change rate from the surface to about 70 ⁇ m is ⁇ 80/40 [0.01 Hv / ⁇ m], that is, ⁇ 2 [0.01 Hv / ⁇ m].
- the hardness change inside the metal material 40 continues from about 1400 Hv of the surface hardness to a hardness of the metal material 40 of 630 Hv. It is preferable to make a transition.
- the hardness change rate from the surface to a depth of about 70 ⁇ m in the 6-hour treatment was ⁇ 2 [0.01 Hv / ⁇ m], but from about 70 ⁇ m from the surface. In a deep part, it changes greatly with ⁇ 22.3 [0.01 Hv / ⁇ m].
- the change ratio is ⁇ 22.3 / ⁇ 2 ⁇ 11.2.
- the change ratio is the ratio of the hardness change rate before and after the point at which the hardness change rate in the nitrogen diffusion layer 40D changes discontinuously (hereinafter referred to as the refraction point).
- the rate of change in hardness is used as the denominator.
- the hardness change rate from the surface to a depth of about 50 ⁇ m is ⁇ 5.1 [0.01 Hv / ⁇ m] and ⁇ 14.6 [0. 01Hv / ⁇ m], and the change ratio is ⁇ 14.6 / ⁇ 5.1 ⁇ 2.9.
- change ratio 11.2
- the behavior differs between this pseudo-coating and a deeper part. Specifically, it is suggested that in the pseudo-coating and a deeper part than that, destruction occurs due to stress concentration, fatigue, or the like in the vicinity of the boundary.
- the hardness change changes almost continuously when the change ratio is about 1/4 of that of the ion nitriding treatment, so that the above-described breakdown due to stress concentration, fatigue, or the like hardly occurs.
- Neutral nitriding has not only a high surface hardness, but also has a feature that the hardness changes continuously inside the material (ideally, the change ratio is 1 and there is no refraction point). In addition, it is possible to impart high resistance to the material against breakage such as stress concentration and fatigue. In general, in the nitriding treatment, the change ratio is preferably 1 to 3.
- Such an effect is considered to be achieved by a combination of a pretreatment process for performing a shot blasting process in which the elastic body 2 collides with the surface of the metal material 40 for a mirror finish and a neutral nitriding process.
- the above-described effect is considered to occur because there are many dislocations excited by the collision of the elastic body 2 inside.
- this dislocation is also present in a normal metal material, more dislocations than those in a normal metal material are generated due to the collision of the elastic body 2, and the dislocation per unit area (dislocation density). Will increase.
- nitrogen atoms implanted into the surface of the metal material 40 will eventually be saturated, the room for nitrogen atoms will decrease, and a nitrogen compound layer 40C will be formed on the surface.
- the metal material 40 in which the dislocation density is increased by performing the pretreatment with the elastic body 2 nitrogen atoms that have started to penetrate from the surface successively propagate through the dislocation lines and diffuse into the metal material 40.
- the nitrogen atoms permeate deeper and more quickly into the interior, so that compared to the conventional nitriding method in which the pretreatment is not performed, in a very short time.
- the desired hardness can be obtained.
- nitrogen atoms penetrate deeper and the nitrogen diffusion layer 40D can be formed thicker.
- the state where the dislocation density is high can contribute to lowering the processing temperature because the nitrogen atoms can be carried into the metal material 40 even in a low processing temperature environment as compared with the conventional method. Furthermore, even for stainless steel materials that have been considered difficult for conventional methods, the penetration of nitrogen atoms can be achieved without damaging the passive layer by utilizing the effect of introducing dislocations. Along with this, corrosion resistance and high surface hardness are obtained. Furthermore, high wear resistance is exhibited even in a corrosive atmosphere.
- the surface roughness of the metal material 40 is literally 50 nm (nanometer) or less in terms of the 10-point average roughness Rz of mirror finishing. It is considered that the above effect is also produced.
- the ten-point average roughness Rz means that only the reference length is extracted from the roughness curve in the direction of the average line, and measured from the average line of the extracted portion in the direction of the vertical magnification, from the highest peak to the fifth. The sum of the absolute value of the absolute value of the altitude of the summit of the mountain and the average value of the absolute values of the altitude of the bottom of the valley from the lowest valley floor to the fifth are obtained, and this value is expressed.
- the ten-point average roughness Rz of the untreated metal material 40 is usually expressed in ⁇ m (micrometer).
- the surface hardening treatment method of the embodiment is a process for forming a concave portion on the surface of the metal material 40 by colliding an inelastic projectile such as a commonly used iron ball or ceramic particle. It has very different characteristics from the method.
- nitrogen atoms are incident from the surface of the metal material 40. Therefore, if the surface area is large, the incident nitrogen atoms increase accordingly.
- the nitrogen atoms incident on the metal material 40 permeate and accumulate inside the metal material 40 mainly along the dislocation lines as described above.
- the incident amount is larger than the permeation amount, It is not preferable because it mainly accumulates in the vicinity and leads to an increase in the change ratio described above.
- concentration of a nitrogen atom becomes high, it will lead also to the production
- the surface area of the metal material 40 is reduced from tens of times to one hundredth. Is possible.
- the incidence of nitrogen atoms is limited, the amount of nitrogen atoms incident and the amount of penetration of nitrogen atoms are balanced, and nitrogen atoms do not stay and penetrate into the metal material 40, contributing to a reduction in change ratio. It is thought to do. That is, in the pretreatment with the elastic body 2, the ten-point average roughness Rz of the metal material 40 is desirably 50 nm or less, and more desirably 30 nm or less.
- the present invention is not limited to the embodiments described with reference to the above description and drawings.
- the following embodiments are also included in the technical scope of the present invention.
- (1) In the above embodiment, a cage produced by weaving a wire into a shielding member is used. However, the cage diameter and the weaving interval may be appropriately changed.
- diamond abrasive grains of 1 ⁇ m or less were used as the abrasive grains of the elastic body. Also good.
- the resin is used as the base material of the elastic body.
- the present invention is not limited thereto, and an elastic body such as rubber may be used.
- the shot blasting process conditions in the pretreatment process, the projection speed of the elastic body, and the collision energy to the metal material may be appropriately changed.
- Shot material (elastic body) 10 ... Processing tank 30 ... Cage (shielding member) 40 ... Sample (metal material, pretreated metal material) 40C ... Nitrogen compound layer 40D ... Nitrogen diffusion layer
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Abstract
Description
母材に浸窒処理を行うことでその表層を硬化させた金属材であって、
前記母材の前記表層には窒素化合物層が形成されておらず、
かつ、前記母材の表面より78μmの深さまでのビッカース硬度が前記母材に比べて5%以上高いことを特徴とする。
弾性体を金属材の表面に衝突させるショットブラスト処理による前処理工程と、
前記前処理工程を経た前処理済み金属材を処理槽内に配し、前記処理槽内に導入した窒素ガスに対して電子ビームを照射することで発生する窒素プラズマによって、前記金属材の表層に窒素拡散層を形成する窒化処理工程とを有することを特徴とする。
表層を硬化させるサンプル(金属材)40として、金属や工具に使用される工具鋼SKD61を用いた。サンプル40は円板状であり、直径は20mmであり、厚さは2mmである。
(1)上記実施例では、遮蔽部材に線材を編み込んで作製したケージを使用したが、ケージの直径や編み込みの間隔は適宜変更しても良い。
(2)プラズマ窒化装置の処理条件及び金属材及びケージに印加するバイアス電圧等は適宜変更しても良い。
(3)上記実施例では、金属材に工具鋼SKD61を使用したがその他の金属及び合金であっても良い。
(4)上記実施例では、弾性体の砥粒として1μm以下のダイヤモンド砥粒を使用したが、粒径は変更しても良く、また、炭化ケイ素やアルミナや窒化ホウ素等の砥粒を用いても良い。
(5)上記実施例では、弾性体の母材として樹脂を用いたが、これに限らず、ゴム等の弾性体を用いても良い。
(6)前処理工程におけるショットブラスト処理条件及び弾性体の投射速度、金属材への衝突エネルギーも適宜変更しても良い。
10…処理槽
30…ケージ(遮蔽部材)
40…サンプル(金属材、前処理済み金属材)
40C…窒素化合物層
40D…窒素拡散層
Claims (5)
- 母材に浸窒処理を行うことでその表層を硬化させた金属材であって、
前記母材の前記表層には窒素化合物層が形成されておらず、
かつ、前記母材の表面より78μmの深さまでのビッカース硬度が前記母材に比べて5%以上高いことを特徴とする表層を硬化させた金属材。 - 前記表層の硬度変化が連続的に推移することを特徴とする請求項1記載の金属材。
- 弾性体を金属材の表面に衝突させるショットブラスト処理による前処理工程と、
前記前処理工程を経た前処理済み金属材を処理槽内に配し、前記処理槽内に導入した窒素ガスに対して電子ビームを照射することで発生する窒素プラズマによって、前記前処理済み金属材の表層に窒素拡散層を形成する窒化処理工程とを有することを特徴とする表層硬化処理方法。 - 前記窒化処理工程は、前記窒素プラズマのうち、窒素イオンの前記前処理済み金属材の前記表面への入射を遮蔽し、窒素原子のみを前記表面に入射させて前記表層に前記窒素拡散層を形成することを特徴とする請求項3記載の表層硬化処理方法。
- 前記窒化処理工程は、前記前処理済み金属材を包囲した遮蔽部材が設けられ、この遮蔽部材によって、前記窒素イオンの前記前処理済み金属材の前記表面への入射が遮蔽されることを特徴とする請求項4記載の表層硬化処理方法。
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JP2020132922A (ja) * | 2019-02-15 | 2020-08-31 | 中日本炉工業株式会社 | プラズマ窒化方法 |
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DE112013006225B4 (de) | 2019-07-18 |
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