JPH1150104A - Production of powder coated with non-magnetic stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively produce a powder coated with non-magnetic stainless steel, having stabilized austenitic structure while obviating the necessity of the use of a target containing large amounts of expansive Ni, by incorporating N effective as an austenite-forming element from an atmosphere into a coating layer. SOLUTION: Powder grains are coated with stainless steel by a sputtering method while rotating a rotating barrel charged with the powder grains at >=0.1 m/min peripheral speed. At this time, N2 gas is mixed at 5-50% partial pressure ratio into the reduced-pressure atmosphere during sputtering to form a coating layer where the crystallite diameter computed from the half-width of X-ray diffraction peak of coating layer is regulated to 5-100 nm and also the Ni equipment Nieq , computed from Nieq =[%Ni]+30×[%C]+0.5×[% Mn]+25×[%M], is regulated to 6-30 mass %. The coating layer has a stainless steel composition containing, e.g. by mass >=4% Ni, 12-30% Cr, and >=0.05% N.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder coated with non-magnetic stainless steel, which is useful as electronic equipment parts, magnetic recording media and their peripheral structures.

[0002]

2. Description of the Related Art It has been known that a stainless steel coating excellent in corrosion resistance and surface properties is applied to a steel plate, a glass substrate, a metal member, a ceramic member, and the like by a sputtering method. However, coating on powders such as metal, glass, and ceramics is not common. In this respect, a powder sputtering method developed by the present applicant (Japanese Patent Laid-Open No.
No. 68, JP-A-5-271920) can be said to be suitable as a method for coating powder. In this method, a fluidized bed of powder is formed by rotation of a rotary barrel filled with powder, and the fluidized bed is subjected to sputtering to coat the surface of powder particles with a metal or the like.
At this time, a coating layer having the target composition is formed on the surface of the powder particles by adjusting the composition and combination of the target according to the target composition of the coating layer.

[0003]

However, when a nonmagnetic stainless steel coating is formed by a sputtering method using an austenitic stainless steel as a target, the composition of the coating layer is low because the sputtering rate of Ni is lower than that of Cr. Shift to low Ni side. In addition, since the coating layer constituent material applied to the surface of the powder particles in a high energy state becomes a coating layer by receiving a kind of quenching effect, a large internal strain is easily generated in the formed coating layer. As a result, the coating layer may undergo a work-induced martensitic transformation to become a magnetic material. That is, even if the amount of Ni is increased for a non-magnetic material, magnetism is eventually generated by martensitic transformation, and the desired characteristics cannot be obtained.

[0004] The formation of a magnetic material in the coating layer can be prevented by using a target containing a large amount of Ni and increasing the Ni content of the coating layer. However, a large amount of expensive Ni is consumed, which causes an increase in the manufacturing cost and thus the cost of the coating powder. The present invention has been devised to solve such a problem. By using a sputtering atmosphere having a high N ₂ partial pressure and incorporating N effective as an austenite forming element from the atmosphere into the coating layer,
Even without using expensive Ni-rich targets,
An object of the present invention is to inexpensively produce a nonmagnetic stainless steel-coated powder having a stabilized austenite structure.

[0005]

According to the present invention, in order to achieve the object, a rotating barrel loaded with powder particles is rotated at a peripheral speed of 0.
When coating the powder particles with stainless steel by sputtering while rotating at a speed of 1 m / min or more, N ₂ gas is mixed in a reduced pressure atmosphere during sputtering at a partial pressure ratio of 5 to 50%,
The crystallite diameter calculated from the X-ray diffraction half width at half maximum of the coating layer is 5 to 100 nm or less, and _Nieq = [% Ni] +3
The coating layer is characterized in that the coating layer has a Ni equivalent Ni _eq calculated by 0 × [% C] + 0.5 × [% Mn] + 25 × [% N] in the range of 6 to 30% by mass. The Ni equivalent Ni _eq of the coating layer is preferably in the range of 7 to 15% by mass. The coating layer is, for example, Ni: 4% by mass or more, Cr: 1
It has a stainless steel composition containing 2 to 30% by mass and N: 0.05% by mass or more. Such a coating layer is formed by using as a target electrode a stainless steel or a mixture whose composition is adjusted in consideration of a sputtering rate, a composite electrode combining a plurality of metals, or the like.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For powder sputtering, for example, FIG.
The following device is used. In this powder sputtering apparatus, a rotary barrel 1 is supported by two rolls 2, and one of the rolls 2 is rotated by a motor 3. Inside the rotary barrel 1, two sputtering sources 4 are arranged. As the sputtering source 4, an austenitic stainless steel or a mixture adjusted to a composition corresponding to a target composition of the coating layer, a composite electrode combining a plurality of different metals, or the like is used as a target. Internal rotating barrel 1 is maintained at a partial pressure ratio in an atmosphere containing 5-50% of N _2. By adjusting the partial pressure ratio, N necessary for stabilizing the austenite structure is taken into the coating layer.
At a partial pressure ratio of less than 5%, less N is introduced into the coating layer, and the formed coating layer tends to become a magnetic material. But 5
If the partial pressure ratio exceeds 0%, the coating structure becomes irregular, the internal stress increases, and unreacted gas is mixed. As a result, the coating state deteriorates and the coating speed decreases.

Above the rotary barrel 1, a decompression processing chamber 7 having a heating coil 6 on its outer periphery is arranged. The bottom of the decompression processing chamber 7 is connected to the rotary barrel 1 via a supply pipe 9 provided with a valve 8. At a position below the valve 8, a gas introduction pipe 10 having a double pipe structure is inserted inside the supply pipe 9. The gas introduction pipe 10 is inserted into the inside of the rotary barrel 1 from the side, and the tip extends to the bottom of the rotary barrel 1. A branch pipe 11 is provided in the supply pipe 9 at a position below the valve 8, and a tip of the branch pipe 11 is connected to the fluid jet mill 12. The outlet side of the fluid jet mill 12 is connected to the upper part of the decompression processing chamber 7 via the circulation pipe 13. A valve 14 and a valve 15 are incorporated in the branch pipe 11 and the circulation pipe 13, and a solid-gas separation device 16 is connected to the circulation pipe 13.

The powder raw material 5 charged in the rotary barrel 1 is
Although there is no particular restriction on the type and material, glass, titanium oxide, alumina, titanium, aluminum,
Mica or the like is used. After a predetermined amount of the powder raw material 5 is charged into the rotary barrel 1 and the pressure in the decompression processing chamber 7 is reduced, an Ar gas containing N ₂ is introduced into the rotary barrel from the gas introduction pipe 10. The powder raw material 5 includes a branch pipe 11, a fluid jet mill 12
Then, it is heated by the heating coil 6 in the decompression processing chamber 7 via the circulation pipe 13, and after being dried and degassed, dropped into the rotary barrel 1. The powder material 5 is sputtered by the sputtering source 4 under a reduced pressure atmosphere while rotating the rotary barrel 1 at a peripheral speed of 0.1 m / min or more under these conditions. The peripheral speed of the rotary barrel 1 greatly affects the stirring state of the powder raw material 5. In order to form a flow state suitable for sputtering, a peripheral speed of 0.1 m / min or more is required. 0.1m /
At a peripheral speed that does not reach the minimum, the powder raw material 5 does not sufficiently fluidize, and the ratio of uncoated powder particles remaining increases.

After a predetermined time has elapsed, the sputtering is stopped, the pressure in the decompression processing chamber 7 is reduced, and
, A mixed gas of Ar and N ₂ is introduced, and the powder raw material 5 is sucked and returned to the decompression processing chamber 7 via the fluid jet mill 12 to loosen the powder raw material 5 which has been agglomerated during sputtering as much as possible into individual particles. By repeating this sputtering operation several times, a coating layer having a predetermined thickness is formed on the surface of the powder raw material 5. The powder having the coating layer formed to a predetermined thickness is recovered from the solid-gas separation device 16. When a non-magnetic stainless steel coating layer is formed on the powdered raw material 5 by such sputtering, the coating layer having a uniform crystallite diameter of 5 to 100 nm calculated from the X-ray diffraction peak half width of the coating layer is required. Needed to form. The crystallite diameter calculated from the half-width of the X-ray diffraction peak of the coating layer corresponds to the crystal grain size constituting the coating layer. In general, in the case of a vapor deposition structure such as the present method, a columnar or Precipitates in granular form. Therefore, the crystallite diameter means the size of such a columnar or granular crystal phase, and by setting this to 100 nm or less, the generation of coarse columnar crystals or coarse granular crystals that hinder uniform coating on the substrate is suppressed. And a good coating can be formed.

When the crystallite diameter exceeds 100 nm, the free energy of the deposited layer decreases and approaches a more equilibrium state. As a result, N forms a non-equilibrium solid solution to stabilize the austenite structure.
Decreases in the amount of solid solution and magnetism develops. Conversely, the crystallite diameter is 5
If the thickness does not reach nm, the internal stress increases, and magnetism is easily developed by the precipitation of work-induced martensite. Further, in the case of an amorphous structure in which the crystallite diameter can be considered to be 0 nm in theory, magnetism is not exhibited in the composition range specified in the present invention. Ni _eq = [% Ni] + 30 × [% C] +
Ni calculated by 0.5 × [% Mn] + 25 × [% N]
The equivalent Ni _eq is adjusted in the range of 6 to 30% by mass from the viewpoint of stabilizing the austenite structure. Ni equivalent N
When i _eq is regulated in this manner, the austenitic nonmagnetic coating layer is formed stably without the need to use a target containing a large amount of Ni. Ni equivalent Ni _eq is 6% by mass
If it is less than 3, the coating layer is likely to be magnetic. Conversely, a Ni equivalent Ni _eq exceeding 30% by mass is effective for non-magnetism, but requires a large amount of Ni, resulting in an increase in cost.

Examples of the composition of the coating layer include a stainless steel composition containing Ni: 4% by mass or more, Cr: 12 to 30% by mass, and N: 0.05% by mass or more. The relationship between the main elements constituting stainless steel and the structure is generally shown by the structure diagram of Schaeffler (FIG. 2). In the case of a film deposited with a sputtering gas containing N ₂ , a non-equilibrium structure is obtained and austenite stability is obtained. As a result, the austenite phase is greatly expanded. When sputtering under the conditions specified in the present invention, Ni
When the equivalent is 6% by mass or more, the formation of martensite and ferrite is suppressed. However, even in this case N
If i is not contained in an amount of 4% by mass or more, magnetism develops due to the formation of the Fe—N compound. Further, when the N content is 0.08% by mass or more when the Ni content is 4% by mass or more, the Ni equivalent _Nieq becomes 6% by mass or more, and other C, M
Even without an element such as n, the austenite phase is sufficiently stabilized. If the Cr content is less than 12% by mass, magnetism may be developed due to precipitation of a martensite phase, and the corrosion resistance of stainless steel decreases. However, when the Cr content exceeds 30% by mass, a ferrite phase is likely to precipitate, which causes an increase in cost.

[0012]

【Example】

Example 1 Powders of various particle sizes were coated with an alloy having a stainless steel composition satisfying the conditions specified in the present invention by a powder sputtering method, and the magnetism and coating state were investigated. Regarding magnetism, the magnetic permeability of the coated powder was measured, and the magnetic permeability was 1.00 to 1.00.
In the range of 1.01, the non-magnetic stainless steel layer ○,
Those exhibiting a magnetic permeability exceeding 1.01 were determined to be those having magnetism x. The coating state was investigated only when an insulating raw material was used, and an equivalent amount of stainless steel coating powder and JIS standard SUS304 or 316L powder having an average particle diameter of 50 μm were charged into an insulating die having an inner diameter of 10 mm, and the pressure was measured. 1
After pressing at 0 MPa, the resistance between the upper and lower electrodes was measured.
When the electric resistance value of the stainless steel coating powder is 90% or more of the electric resistance value of the stainless steel powder, the coating state is particularly good. When the electric resistance value is 70% to 90%, the coating state is good. Was determined to be poor in coating condition. As can be seen from the investigation results in Tables 1 to 4, all of the stainless steel-coated powders produced under the conditions specified in the present invention exhibited a good non-magnetic state and a good coating state.

[0013]

[0014]

[0015]

[0016]

Embodiment 2: JIS standard SUS304 as Al ₂ O ₃ having an average particle size of 1 μm as an insulating ceramic powder.
Stainless steel having a considerable composition was coated by a sputtering method to form a film having a Ni equivalent of 10 to 23% by mass. During the sputtering, the partial pressure ratio of the N ₂ gas was maintained at a constant value of 50%, and the barrel peripheral speed was changed. The obtained stainless steel-coated powder was nonmagnetic and had a crystallite diameter of 100 nm or less. When the coating state was evaluated in the same manner as in Example 1, and arranged by the peripheral speed of the barrel, as shown in FIG. 3, when the peripheral speed of the barrel became 0.1 m / min or more, all showed a good coating state. It turns out.

Example 3 Average particle size of 15 as insulating powder
JIS standard SUS3 on flake glass powder of 0 μm
A stainless steel having a composition equivalent to 04 was coated by a sputtering method to form a film having a Ni equivalent of 10 to 23% by mass. The barrel peripheral speed was maintained at a constant value of 0.1 m / min, and the partial pressure ratio of N ₂ gas was changed. The magnetism of the obtained stainless steel coated powder was measured, and the relationship between the non-magnetism and the partial pressure ratio of N ₂ gas was investigated. As can be seen from the investigation results in FIG. 4, when the partial pressure of the N ₂ gas was 5 to 50%, a favorable non-magnetic state and a coated state were obtained. In particular, the partial pressure of N ₂ gas is 30-50.
%, A particularly good coating state was obtained.

Example 4: Average particle size of 15 as insulating powder
JIS standard SUS3 on flake glass powder of 0 μm
A stainless steel having a composition equivalent to 04 was coated by a sputtering method to form a film having a Ni equivalent of 10 to 23% by mass. The barrel peripheral speed was maintained at a constant value of 0.1 m / min, the N ₂ gas partial pressure was maintained at a constant value of 50%, and the crystallite diameter of the coating layer was changed depending on the sputtering conditions. The magnetism and the coating state of the obtained stainless steel coating powder were investigated and arranged in relation to the crystallite diameter. As can be seen from the results in FIG. 5, when the crystallite diameter is in the range of 5 to 100 nm, a favorable non-magnetic state and a coated state are obtained. Above all, 5
An excellent coating state was obtained with a crystallite diameter of 30 nm.

Example 5: Insulating powder having an average particle size of 15
Stainless steel having various compositions was coated on a 0 μm flake glass powder by a sputtering method. Barrel peripheral speed at a constant value of 0.1 m / min, N ₂ gas partial pressure at a constant value of 50%
, And the Ni equivalent in the film was changed. In this example, the crystallite diameter was adjusted to a range of 5 to 100 nm. The magnetism of the obtained stainless steel coated powder was measured, and the relationship with the Ni equivalent in the coating was investigated. As can be seen from the investigation results in FIG. 6, it is understood that a good nonmagnetic powder is obtained when the Ni equivalent is 6% by mass or more. However, when the Ni equivalent exceeds 30% by mass, introduction of N ₂ gas can be omitted, but the cost of the obtained stainless steel-coated powder becomes extremely high.

Example 6: Insulating powder having an average particle size of 15
Stainless steel having various compositions was coated on a 0 μm flake glass powder by a sputtering method. Barrel peripheral speed at a constant value of 0.1 m / min, N ₂ gas partial pressure at a constant value of 50%
, And the amounts of Ni and N in the film were changed. In this example, the crystallite diameter was adjusted to 5 to 100 nm, and the Cr content was adjusted to 18 to 20% by mass.
The magnetism of the obtained stainless steel coated powder was measured, and the relationship between the amount of Ni and the amount of N in the film was investigated. As can be seen from the survey results in FIG.
When the amount is 4% by mass or more and the N amount is 0.05% by mass or more,
It turns out that it has become a favorable nonmagnetic powder.

Example 7: Insulating powder having an average particle size of 15
Stainless steel having various compositions was coated on a 0 μm flake glass powder by a sputtering method. Barrel peripheral speed at a constant value of 0.1 m / min, N ₂ gas partial pressure at a constant value of 50%
, And the Ni equivalent and the Cr amount in the film were changed.
In this example, the crystallite diameter was 5 to 100 nm.
Was adjusted to the range. The magnetism of the obtained stainless steel coated powder was measured, and the relationship between the Ni equivalent and the Cr content in the coating was investigated. As can be seen from the investigation results in FIG. 8, when the Ni equivalent is 6 to 30% by mass and the Cr content is within the range specified in the present invention, it is understood that the nonmagnetic powder is good.

[0023]

As described above, in the present invention, by sputtering in an atmosphere having a high N ₂ partial pressure ratio, N is taken into the coating layer from the atmosphere and a target having a relatively low Ni content is used. Even in this case, a nonmagnetic coating layer having an austenite structure is stably formed on the surface of the powder particles. The nonmagnetic stainless steel-coated powder obtained in this manner can freely select the type and particle size of the base powder and can also select the surface composition, so that it satisfies the constraints of corrosion resistance, cost, etc. It becomes a nonmagnetic powder. Fine powder of 1 μm or less is used for cases and surface treatment of small electronic components, magnetic recording media, etc. by being added to paints and resin compositions. On the other hand, large coating powders exceeding 100 μm are used not only for cases and surface treatment, but also for large electronic components and cases, and furthermore, by utilizing their low electrical resistance, high frequency electromagnetic wave seals, radio wave absorption, etc. It can also be applied to applications.

[Brief description of the drawings]

FIG. 1 shows an example of an apparatus used for powder sputtering.

Fig. 2 Organization chart of Schaeffler

FIG. 3 is a graph showing an effect of a peripheral speed of a barrel on a coating state.

FIG. 4 is a graph showing the effect of the N ₂ gas partial pressure ratio on the non-magnetic state and the coating state.

FIG. 5 is a graph showing the effect of the crystallite diameter of the coating layer on the non-magnetic state and the coating state.

FIG. 6 is a graph showing the effect of Ni equivalent on non-magnetic and coated states.

FIG. 7 is a graph showing the effects of the amounts of Ni and N on non-magnetism.

FIG. 8 is a graph showing the effect of Ni equivalent and Cr content on non-magnetism.

[Explanation of symbols]

1: rotating barrel 2: roll 3: motor
4: sputtering source 5: powder raw material 6: heating coil 7: decompression processing chamber
8: Valve 9: Supply pipe 10: Gas introduction pipe 11: Branch pipe
12: Fluid jet mill 13: Circulation pipe 14: Valve 15: Valve 1
6: Solid-gas separation device

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // G11B 23/04 G11B 23/04 E 33/14 33/14 E (72) Inventor Yosuke Tanaka 7 Takatani-Shimmachi, Ichikawa-shi, Chiba No. 1 Nisshin Steel Co., Ltd.

Claims (2)

[Claims] 1. A rotating barrel loaded with powder particles is rotated at a peripheral speed.
Sputtering while rotating at 0.1m / min or more
When coating powder particles with stainless steel, sputtering
N in a reduced pressure atmosphere_Two Gas mixed at a partial pressure ratio of 5-50%
And the crystal calculated from the half width of the X-ray diffraction peak of the coating layer.
Having a diameter of 5 to 100 nm or less and Ni _eq= [% Ni]
+ 30 × [% C] + 0.5 × [% Mn] + 25 × [%
N] Ni equivalent calculated by N]_eqIs in the range of 6 to 30% by mass.
Forming a surrounding coating layer.
Method for producing powder coated with stainless steel. 2. Ni: 4% by mass or more, Cr: 12 to 30
The method for producing a powder coated with a non-magnetic stainless steel according to claim 1, wherein a stainless steel coating layer containing at least 0.05% by mass of N and 0.05% by mass is formed.