JP2004091838A - Corrosion resistant cermet and pump parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion resistant cermet having adequate corrosion resistance and wear resistance and consequently improved durability, even when used for frictional parts used in a corrosive atmosphere such as in sea water or river water, and to provide pump parts using it. <P>SOLUTION: This cermet includes carbides of WC, Cr<SB>3</SB>C<SB>2</SB>or TiC, which are combined with a metallic binder. The above metallic binder comprises Ni, Co or a mixture thereof, and Cr and one or more metallic elements of a Va group or a VIa group, which are added. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
【発明の効果】
以上説明したように、本発明によれば、サーメットの金属バインダとして、Ｎｉ、Ｃｏまたはそれらの混合物からなる基材に、Ｃｒの他に、Ｃｒより炭化物生成エネルギの低いＶａ族またはＶＩａ族の金属元素の一種または一種以上を加えたものを使用することで、Ｃｒ炭化物の生成による基材の消費量を抑えて、耐食性を向上させることができる。これによって、例えばポンプの摺動部材として使用した場合に、主成分の組織の境界での選択腐食の発生を抑え、耐久性を向上させて、その寿命を延ばすことができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態の耐食性サーメットでポンプのすべり軸受の回転側部品（ポンプ部品）を構成した例を示す断面図である。
【図２】本発明の他の実施の形態の耐食性サーメットでポンプのすべり軸受の回転側部品（ポンプ部品）を構成した例を示す断面図である。
【図３】重量の異なるＣｒを含む金属バインダ、ＣｒとＭｏを含む金属バインダ、及びＣｒと、ＭｏとＴａとの混合物を含む金属バインダをそれぞれ使用して成形したＷＣ系サーメット材料の海水中における陽極分極曲線を調べた実験結果を示すグラフである。
【符号の説明】
１０　主軸
１２　軸受スリーブ
１４　固定スリーブ
１６　軸受ブッシュ
１８　バックシェル
２０　緩衝材
２２　軸受ケース[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a corrosion-resistant cermet that is optimally used for a sliding component provided in a pump device installed in water and used by being immersed in water, and a pump component using the corrosion-resistant cermet.
[0002]
[Prior art]
For example, pump devices used to pump seawater, sewage containing halogen ions, river water, and the like mainly use an impeller that rotates and pumps water in water, and an impeller that penetrates water and supplies water. And a bearing used in water (underwater bearing). The underwater bearing has a rotary sliding portion with the main shaft, and its function requires corrosion resistance and wear resistance. Also, in order to prevent leakage of water from the high-pressure section after the impeller outlet to the inlet side of the impeller, a ring called a wear ring is fitted on the rotating side, and a very small distance is formed between the ring and the liner ring fitted on the stationary side. It is also widely practiced that the pump slides against each other with a narrow gap, thereby preventing leakage of pumped water from the high pressure side to the low pressure side and preventing the pump efficiency from being reduced.
[0003]
In many cases, these pump parts have a structure in which the pumped water itself such as seawater is operated in contact with the end surfaces and sliding surfaces of both the fixed side and the rotating side parts, and is conventionally used for seawater. The parts attached to the part where the rotating body and the fixed body mechanically slide (hereinafter simply referred to as sliding parts) include not only metals but also various ceramics from the viewpoint of corrosion resistance and wear resistance. Is commonly used. For example, as a sliding part of the fixed side, such as water bearing or liner rings used in water, the SiC or Si ₃ N ₄ based ceramic, as a sliding part of the rotation-side, such as the shaft sleeve and wear rings, WC-based Combinations using TiC and cermets have been used in seawater and the like. The cermet used for the sliding parts used in water mainly uses carbide of a high melting point metal, for example, Ni or Co as a WC-based metal binder (binder).
[0004]
[Problems to be solved by the invention]
However, for sliding parts used in highly corrosive atmospheres such as seawater and river water, it is the present situation that a completely satisfactory material has not yet been realized in terms of wear resistance and corrosion resistance. For example, as described above, when a WC-based cermet using Co as a metal binder is used for a sliding part of a seawater pump, the Co component of a binder mainly present at the boundary of the WC causes a contact portion between the WC and the main shaft. In this case, corrosion (selective corrosion) is preferentially caused to be released and eliminated, leaving only particles of the WC component, and the portion may become brittle and may be missing.
[0005]
Note that TiC-based cermets using Co, Cu, Fe, Ni, and Ag are known as metal binders. However, any of the bonding materials has low corrosion resistance in a corrosive atmosphere such as seawater. If a TiC-based cermet using such a metal binder is used for a sliding part or the like used in seawater or the like, there is a problem in corrosion resistance. it is conceivable that.
[0006]
The present invention has been made in view of the above circumstances, and has sufficient abrasion resistance and corrosion resistance even when used as a sliding component used in a highly corrosive atmosphere such as seawater or river water, and has improved durability. It is an object of the present invention to provide a corrosion-resistant cermet and a pump component using the corrosion-resistant cermet.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is characterized in that carbide of WC, Cr ₃ C ₂ or TiC is solidified with a metal binder, and the metal binder is composed of Ni, Co or a mixed material thereof, with Cr and Va group. Alternatively, it is a corrosion-resistant cermet characterized by being added with one or more of Group VIa metal elements.
[0008]
The corrosion resistance of the cermet can be improved by using, as a metal binder of the cermet, a substrate made of Ni, Co, or a mixture thereof, to which Cr is added. However, when the content of Cr exceeds 5% by weight, Cr forms carbides and consumes the base material, so that the corrosion resistance of the base material is reduced. Here, in addition to Cr, a metal element of a Va group or a VIa group having a lower carbide generation energy than Cr, for example, one or more of Mo, Ta or Nb is added to a substrate made of Ni, Co or a mixture thereof. By adding Cr, even if the content of Cr exceeds 5% by weight, the formation of Cr carbide can be prevented, and the corrosion resistance can be improved.
[0009]
The invention according to claim 2 is the corrosion-resistant cermet according to claim 1, wherein the metal binder has 5 to 35% by weight of Cr. As described above, mixing a metal element such as Mo or Ta of Va group or VIa group having lower carbide generation energy than Cr with Cr and adding it to a base material such as Ni to prevent generation of Cr carbide. Thus, up to 35% by weight of Cr can be mixed into the metal binder.
[0010]
According to a third aspect of the present invention, the metal element of the group Va or group VIa is Ta or Mo, and the content of Ta is 77.5% by weight or more based on the content of Cr, or the content of Mo is contained in the content of Cr. The corrosion-resistant cermet according to claim 1, wherein the cermet is contained in an amount of 95% by weight or more based on the amount. Assuming that each of the stabilized carbides of Cr, Ta and Mo is Cr ₃ C ₂ , Ta ₂ C and MoC, respectively, about 77.5 wt% or more of Ta and about 95 wt% or more of Mo with respect to the Cr content. By including it, generation of Cr carbide can be effectively prevented.
[0011]
According to a fourth aspect of the present invention, a carbide of WC, Cr ₃ C ₂ or TiC is solidified with a metal binder, and the metal binder is made of Ni, Co or a mixed material thereof containing Cr and Va group. Alternatively, it is a pump component composed of a corrosion-resistant cermet to which one or more of Group VIa metal elements are added.
[0012]
According to a fifth aspect of the present invention, a carbide of WC, Cr ₃ C ₂ or TiC is solidified with a metal binder, and the metal binder is made of Ni, Co or a mixed material thereof containing Cr and Va group. Alternatively, the present invention provides a pump device comprising a pump component formed of a corrosion-resistant cermet to which one or more of Group VIa metal elements are added.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example in which a rotation-side sliding part (pump part) of a sliding bearing of a pump is constituted by a corrosion-resistant cermet according to an embodiment of the present invention. As shown in FIG. 1, for example, a cylindrical bearing sleeve 12 made of the corrosion-resistant cermet of the present invention has a cylindrical fixed sleeve fixed to the main shaft 10 on a rotatable main shaft 10 made of SUS316 and having a stepped portion 10a. It is sandwiched between the main shaft 14 and the step portion 10a of the main shaft 10, and is attached to the main shaft 10 so as to be non-rotatable and axially immovable. That is, the bearing sleeve 12 rotates integrally with the main shaft 10 and is restricted from moving along the axial direction.
[0014]
A cylindrical bearing bush 16 made of ceramics whose main component is, for example, silicon carbide (SiC) or silicon nitride (Si ₃ N ₄ ) is arranged on the outer peripheral portion of the bearing sleeve 12. The back shell 18 is fixed to an inner peripheral surface of the back shell 18, and is incorporated in a bearing case 22 with a cushioning material 20 interposed therebetween on an outer peripheral surface thereof.
As a result, the outer peripheral surface of the bearing sleeve 12 becomes a sliding surface on the rotating side, the bearing sleeve 12 becomes a sliding member on the rotating side, and the inner peripheral surface of the bearing bush 16 becomes a sliding surface on the fixed side. The bush 16 is configured to be a fixed-side sliding component.
[0015]
Here, the bearing sleeve 12 is formed of a corrosion-resistant cermet made of a sintered body obtained by firing a carbide such as WC, Cr ₂ C ₂ or TiC with a metal binder. This metal binder is made of Ni, Co or a mixed material of Ni and Co as a base material, and a base material (Ni base material, Co base material or Ni + Co base material) is provided with Cr, a Va group or VIa group metal element, For example, Nb, Ta or Mo, or a mixture thereof is added.
[0016]
The Cr content in the metal binder is set to, for example, 5 to 35% by weight. Further, in addition to Cr, for example, when Ta of the Va group is added, the Ta is added to the Cr content by 77.5% by weight or more, and when Mo of the VIa group is added, the Mo is added to the Cr content. More than 90% by weight based on the amount.
[0017]
As described above, the corrosion resistance of the cermet can be improved by using a Ni base material, a Co base material, or a Ni + Co base material to which Cr is added as the metal binder of the cermet. In addition, as the metal binder, a mixture of one or more of a metal element of the Va group or the VIa group having lower carbide generation energy than Cr, such as Mo, Ta or Nb, in addition to Cr, is used as the metal binder. For example, by using a material added with an equivalent amount of Cr, even if the content of Cr exceeds 5% by weight, it is possible to prevent the generation of the Cr carbide and consumption of the base material, and to improve the corrosion resistance. In addition, it is possible to mix up to 35% by weight of Cr in the metal binder.
[0018]
When the stabilized carbides of Cr, Ta and Mo are Cr ₃ C ₂ , Ta ₂ C and MoC, respectively, in addition to Cr, Ta is 77.5% by weight or more based on the content of Cr. Alternatively, when Mo is contained in an amount of 95% by weight or more with respect to the Cr content, generation of Cr carbide can be effectively prevented.
[0019]
FIG. 2 shows an example in which a rotation-side sliding part (pump part) of a sliding bearing of a pump is constituted by a corrosion-resistant cermet according to another embodiment of the present invention. This embodiment differs from the embodiment shown in FIG. 1 in that a cylindrical bearing sleeve 12 made of the corrosion-resistant cermet of the present invention is provided between a flange portion 10b of a main shaft 10 and a fixed sleeve 14 fixed to the main shaft 10. This is a point that it is held so as not to rotate with respect to the main shaft 10 and to be unable to move in the axial direction. The other configuration is the same as that of the embodiment shown in FIG. 1 and is not shown here.
[0020]
In addition, in each of the above examples, the present invention is applied to a bearing sleeve as a rotating-side sliding part and is used in combination with a ceramic bearing bush as a fixed-side sliding part. An example is shown in which the life is longer than that of a bearing.However, it can be applied to both a bearing sleeve as a rotating side sliding part and a bearing bush as a fixed side sliding part. May be used in combination with a bearing sleeve made of ceramics as a rotating side sliding part.
[0021]
Furthermore, among pump parts, there are many parts in which a rotating part and a fixed part slide underwater, such as a wear ring and a liner part of an impeller, and a cermet is originally excellent in wear resistance. Therefore, it can be applied to these parts by increasing the corrosion resistance of the metal binder. In addition, in the case of sewage and sewage other than seawater, the concentration of halogen ions is lower than that of seawater. Therefore, as long as other ions are not contained in large amounts, they can be applied to sliding parts of pumps used for pumping these waters. it can.
[0022]
FIG. 3 shows that 4.8% by weight, 5.3% by weight, 6.4% by weight, 8.2% by weight, 11.8% by weight, and 25% by weight of Cr were added to a Ni base material or a Ni + Co base material. A WC-based cermet material formed using a metal binder containing 6.5 wt% of Cr and 6.5 wt% of Mo in a Ni base material; Anodic polarization curve in sea water of a WC-based cermet material molded using a metal binder containing a mixture of 13.5% by weight of Cr and 11.5% by weight of Mo and Ta in a Ni + Co base material Experimental results are shown. Here, the vertical axis indicates the current density and corresponds to the corrosion rate. The horizontal axis indicates the magnitude of the activation energy in terms of the potential.
[0023]
According to FIG. 3, as the Cr addition amount increases, the current density decreases and the corrosion rate decreases in the low activation energy region. However, as the activation energy increases, 4.8% by weight or more of Cr is included. In the case of a cermet material formed using a metal binder, peaks in current density occur at potentials of around 300 mV and around 700 to 800 mV. This indicates that in an actual environment, severe corrosion occurs near the peak due to the bearing mounting material and the supply state of oxygen.
[0024]
On the other hand, in a WC-based cermet material formed using a metal binder containing 6.5% by weight of Cr and 6.5% by weight of Mo in a Ni base material, and in a Ni + Co base material, 13. In a WC cermet material formed using a metal binder containing a mixture of 5% by weight of Cr and 11.5% by weight of Mo and Ta, no current density peak occurs in a corresponding potential region. It shows that it shows high corrosion resistance.
[0025]
The components and mechanical properties of each cermet material used at this time are shown in Table 1 below.
[Table 1]

[0026]
【The invention's effect】
As described above, according to the present invention, as a metal binder for a cermet, a base made of Ni, Co, or a mixture thereof, in addition to Cr, a Va group or VIa group metal having a lower carbide generation energy than Cr. By using one or more of the elements, the consumption of the substrate due to the generation of Cr carbide can be suppressed, and the corrosion resistance can be improved. Thereby, for example, when used as a sliding member of a pump, it is possible to suppress the occurrence of selective corrosion at the boundary of the structure of the main component, improve the durability, and extend the life.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example in which a rotation-side component (pump component) of a sliding bearing of a pump is formed by a corrosion-resistant cermet according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating an example in which a rotation-side component (pump component) of a sliding bearing of a pump is formed by a corrosion-resistant cermet according to another embodiment of the present invention.
FIG. 3 shows a WC-based cermet material formed using a metal binder containing Cr, a metal binder containing Cr and Mo, and a metal binder containing a mixture of Cr, Mo and Ta, respectively, in seawater having different weights. 5 is a graph showing an experimental result obtained by examining an anodic polarization curve.
[Explanation of symbols]
Reference Signs List 10 Main shaft 12 Bearing sleeve 14 Fixed sleeve 16 Bearing bush 18 Back shell 20 Shock absorber 22 Bearing case

Claims (5)

WC, Cr ₃ C ₂ or TiC carbide is solidified with a metal binder, and the metal binder is made of Ni, Co or a mixed material thereof, and Cr and one of Va group or VIa group metal elements or Corrosion resistant cermet characterized by adding at least one kind. The corrosion resistant cermet according to claim 1, wherein the metal binder has 5 to 35% by weight of Cr. The group Va or group VIa metal element is Ta or Mo, and contains Ta in an amount of 77.5% by weight or more based on the Cr content, or Mo in an amount of 95% by weight or more based on the Cr content. The corrosion-resistant cermet according to claim 1 or 2, wherein: WC, Cr ₃ C ₂ or TiC carbide is solidified with a metal binder, and the metal binder is made of Ni, Co or a mixed material thereof, and Cr and one of Va group or VIa group metal elements or Pump parts composed of corrosion resistant cermets, which are one or more types. WC, Cr ₃ C ₂ or TiC carbide is solidified with a metal binder, and the metal binder is made of Ni, Co or a mixed material thereof, and Cr and one of Va group or VIa group metal elements or A pump device comprising a pump component formed of a corrosion-resistant cermet, which is obtained by adding at least one type.

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