阅读说明：本技术 耐热烧结合金材料 (Heat-resistant sintered alloy material ) 是由 丹野瑞成 鹰木清介 于 2019-09-02 设计创作，主要内容包括：本发明提供适合于涡轮增压器用部件等的耐热烧结合金材料。耐热烧结合金材料,其具有：以质量%计包含C：1.0～3.5%、Si：2.0～3.5%、P：0.3～1.0%、Cr：15～32%、Ni：14～25%、Mo：1.5～4.9%、Nb：0.5～4.0%、W：0.5～6.1%、或者进一步含有Cu：1.0～3.5%、且余量由Fe和不可避免的杂质构成的组成；以及基体相为奥氏体相、且碳化物析出、或者进一步分散有固体润滑剂颗粒的组织,硬度以HRA计为55～75,密度为7.2g/cm<Sup>3</Sup>以上。本发明的耐热烧结合金材料的耐热性、耐磨损性、以及耐氧化性优异,适合作为喷嘴体或衬套等涡轮增压器用部件。(The invention provides a heat-resistant sintered alloy material suitable for a turbocharger member and the like. A heat resistant sintered alloy material having: contains C: 1.0-3.5%, Si: 2.0-3.5%, P: 0.3-1.0%, Cr: 15-32%, Ni: 14-25%, Mo: 1.5-4.9%, Nb: 0.5-4.0%, W: 0.5 to 6.1%, or further contains Cu: 1.0 to 3.5%, and the balance of Fe and unavoidable impurities; and a structure in which the matrix phase is an austenite phase, and a carbide is precipitated or solid lubricant particles are further dispersed, the hardness is 55 to 75 in HRA, and the density is 7.2g/cm 3 The above. The heat-resistant sintered alloy material of the present invention is excellent in heat resistance, wear resistance and oxidation resistance, and is suitable for use as a nozzleA turbocharger member such as a body or a sleeve.)

1. A heat-resistant sintered alloy material characterized by comprising:

comprises by mass%: c: 1.0-3.5%, Si: 2.0-3.5%, P: 0.3-1.0%, Cr: 15-32%, Ni: 14-25%, Mo: 1.5-4.9%, Nb: 0.5-4.0%, W: 0.5 to 6.1%, and the balance of Fe and unavoidable impurities; and

the matrix phase is an austenite phase and has a structure in which carbides are precipitated,

the hardness is 55-75 in HRA and the density is 7.2g/cm³The above.

2. The heat resistant sintered alloy material according to claim 1, characterized in that: the structure is formed such that the matrix phase is an austenite phase, carbides are precipitated, and solid lubricant particles are further dispersed.

3. The heat resistant sintered alloy material according to claim 2, characterized in that: in addition to the above composition, a composition further containing Mn in mass%: 3.2% or less and S: 2.0% or less.

4. The heat resistant sintered alloy material according to claim 2, characterized in that: in addition to the above composition, a composition further containing, in mass%: 2.0% or less.

5. The heat-resistant sintered alloy material as set forth in any one of claims 1 to 4, characterized in that: in addition to the above composition, a composition further containing Cu: 1.0 to 3.5% of the composition.

6. A turbocharger component produced from the heat-resistant sintered alloy material according to any one of claims 1 to 5.

Technical Field

The present invention relates to a sintered alloy material, and particularly to a heat-resistant sintered alloy material suitable for a turbocharger component or the like attached to an internal combustion engine.

Background

In recent years, exhaust gas control has been intensified, and in particular, improvement of fuel consumption rate of automobiles has been strongly demanded. Under such circumstances, a turbocharger that rotates a turbine by exhaust gas of an internal combustion engine (engine) and supplies high-pressure air to the engine by driving a compressor provided coaxially with the turbine has a great effect in improving the fuel consumption rate of the internal combustion engine (engine), and is an important device for the internal combustion engine (engine).

Recently, in order to increase the speed and output of an internal combustion engine, further improvement in the reliability and durability of a turbocharger is strongly demanded. Therefore, in particular, there is a demand for improvement in high temperature characteristics such as heat resistance and high temperature wear resistance of the turbocharger member exposed to a high temperature gas atmosphere.

For such requirements, for example, heat-resistant castings or various heat-resistant sintered alloys specified in DIN specifications as EN10295 are used. As an example of using a heat-resistant sintered alloy, patent document 1 proposes "a turbine component for a turbocharger". The turbine member described in patent document 1 is a turbine member for a turbocharger, and is characterized in that: the alloy consists of Cr: 23.8 to 44.3%, Mo: 1.0-3.0%, Si: 1.0-3.0%, P: 0.1-1.0%, C: 1.0 to 3.0% and the balance of Fe and inevitable impurities, the density ratio being 95% or more, and the carbide being dispersed in the matrix. This greatly improves the corrosion resistance, and improves the wear resistance and oxidation resistance of the turbine component.

In addition, patent document 2 proposes "a method of manufacturing a component from a metal powder". The technique described in patent document 2 is a method for manufacturing a member including the steps of: providing a metal powder containing 0 to 0.6% by weight of carbon, 0.5 to 5.0% by weight of silicon, 0.5 to 6.0% by weight of nickel, 0.5 to 1.5% by weight of molybdenum, 0 to 0.7% by weight of manganese, and 12 to 20% by weight of chromium; a step of compressing the metal powder at a pressure of 35 to 65tsi to obtain an unsintered green compact; and heating the green compact at a temperature of 2100 to 2400 ℃ for 20 to 90 minutes so as to obtain a green compact in which the microstructure (structure) is a two-phase structure composed of a ferrite phase and an austenite phase or a single-phase structure composed of only a ferrite phase. Thus, a member excellent in heat resistance and corrosion resistance can be obtained.

Patent document 3 proposes a "method for producing a sintered machine component". The technique described in patent document 3 is a method for manufacturing a sintered machine component, which includes: the alloy is prepared from the following components in percentage by mass: 25-45%, Ni: 8-16.0%, Mo: 0.8-2.8%, Si: 0.8-2.8%, C: 0.5 to 3.0% and the balance Fe and inevitable impurities, 1.0 to 5.0% by mass of Fe-P powder having a P content of 10 to 30% by mass and 0.5 to 3.0% by mass of graphite powder are mixed to obtain a mixed powder, and the mixed powder is molded and sintered. Thus, a sintered mechanical part having a metal structure in which fine particulate carbides are dispersed in an austenite matrix is obtained, and the high-temperature strength can be improved together with the heat resistance, corrosion resistance, and wear resistance, and a part having a coefficient of thermal expansion equivalent to that of austenitic heat-resistant steel can also be obtained.

In addition, patent document 4 proposes "sintered alloy". The sintered alloy described in patent document 4 is a sintered alloy characterized by exhibiting the following metal structure: a composition consisting of Cr: 11.75-39.98%, Ni: 5.58-24.98%, Si: 0.16-2.54%, P: 0.1-1.5%, C: 0.58 to 3.62%, and the balance of Fe and inevitable impurities, and has an average particle diameter of 10 to 50μm metal carbide phase A precipitated with an average particle diameter of 10μPhase B of metal carbide of m or less is distributed in a spot-like manner, and the average particle diameter DA of the metal carbide precipitated in the phase A and the average particle diameter DB of the metal carbide precipitated in the phase B are DA>And (7) DB. The sintered alloy described in patent document 4 may further contain 5% or less of at least 1 selected from Mo, V, W, Nb, and Ti. Thus, the steel sheet has excellent machinability while having excellent heat resistance, corrosion resistance and wear resistance at high temperatures, and shows excellent machinabilityThe heat-resistant steel has a coefficient of thermal expansion equivalent to that of austenitic heat-resistant steel, and the design of parts is facilitated.

Disclosure of Invention

Problems to be solved by the invention

However, the heat-resistant cast product specified in the DIN specification is highly alloyed, is poor in workability, is expensive, and has a problem that it cannot meet the recent demand for cost reduction. On the other hand, the techniques described in patent documents 1 and 2 relate to ferrite materials, and have a problem that, when used as a member requiring heat resistance, such as a turbocharger member, the member has a different thermal expansion coefficient from the surrounding austenite material, and the design of the member becomes difficult.

Further, according to the techniques described in patent documents 3 and 4, a material having an austenite matrix can be obtained, and the material exhibits a thermal expansion coefficient equivalent to that of the austenitic heat-resistant steel, and can facilitate the design of parts. However, the techniques described in patent documents 3 and 4 have a problem that the wear resistance at high temperatures is insufficient as the exhaust gas temperature is further increased recently.

The present invention has been made in view of the above-mentioned problems of the conventional art, and an object of the present invention is to provide a heat-resistant sintered alloy material having excellent wear resistance suitable for a turbocharger member or the like attached to an internal combustion engine. Recently, since there is a high demand for improvement in fuel consumption of automobiles, exhaust gas temperature is increased in parts for turbochargers, and abrasion resistance, particularly at high temperatures, is insufficient in conventional parts materials. Accordingly, an object of the present invention is to provide a heat-resistant sintered alloy material having improved wear resistance particularly at high temperatures.

Means for solving the problems

In order to achieve the above object, the present inventors have conducted intensive studies on various factors affecting the high-temperature wear resistance of the heat-resistant sintered alloy material. As a result, it is important to include an appropriate amount of alloy elements such as Cr and Ni, to make the matrix structure an austenite phase to improve heat resistance, and to reduce voids to form a sintered body having a density of a predetermined value or more in order to improve wear resistance at high temperatures.

Therefore, it is thought that the content (addition amount) of P, C needs to be adjusted to an appropriate amount to cause liquid phase sintering, and Cr carbide and Nb and W carbide need to be finely dispersed in the austenite matrix phase. Further, it is also conceivable that Mo is contained or Cu is further contained to increase the hardness to achieve both excellent high-temperature strength.

The present invention has been completed by further studies based on the above findings. Namely, the gist of the present invention is as follows.

(1) A heat-resistant sintered alloy material characterized by comprising:

contains C: 1.0-3.5%, Si: 2.0-3.5%, P: 0.3-1.0%, Cr: 15-32%, Ni: 14-25%, Mo: 1.5-4.9%, Nb: 0.5-4.0%, W: 0.5 to 6.1%, and the balance of Fe and unavoidable impurities; and

the matrix phase is an austenite phase and has a structure in which carbides are precipitated,

the hardness is 55-75 in HRA and the density is 7.2g/cm³The above.

(2) The heat-resistant sintered alloy material according to (1), characterized in that: the structure is formed such that the matrix phase is an austenite phase, carbides are precipitated, and solid lubricant particles are further dispersed.

(3) The heat-resistant sintered alloy material according to (2), characterized in that: in addition to the above composition, a composition further containing Mn in mass%: 3.2% or less and S: 2.0% or less.

(4) The heat-resistant sintered alloy material according to (2), characterized in that: in addition to the above composition, a composition further containing, in mass%: 2.0% or less.

(5) The heat-resistant sintered alloy material according to any one of (1) to (4), characterized in that: in addition to the above composition, a composition further containing Cu: 1.0 to 3.5% of the composition.

(6) A turbocharger component produced from the heat-resistant sintered alloy material according to any one of (1) to (5).

Effects of the invention

According to the present invention, a heat-resistant sintered alloy material excellent in heat resistance, wear resistance at high temperatures, and oxidation resistance and suitable as a turbocharger component such as a nozzle body or a liner, and excellent in heat resistance, wear resistance, and oxidation resistance can be easily produced, and industrially significant effects are exhibited.

Drawings

FIG. 1 is an explanatory view schematically showing the outline of a high-temperature wear test performed in examples.

Detailed Description

The heat-resistant sintered alloy material of the present invention has a composition containing, in mass%, C: 1.0-3.5%, Si: 2.0-3.5%, P: 0.3-1.0%, Cr: 15-32%, Ni: 14-25%, Mo: 1.5-4.9%, Nb: 0.5-4.0%, W: 0.5 to 6.1%, and the balance of Fe and inevitable impurities.

First, the reasons for the limitation of the composition will be explained. Hereinafter, "mass%" is simply referred to as "%".

C：1.0～3.5%

C is an element that forms a liquid phase (Fe-P-C) together with P to contribute to increase the density of the sintered body. In addition, C bonds with carbide-forming elements such as Cr and Mo to form carbide, and contributes to improvement of wear resistance. In order to obtain such an effect, it is necessary to contain 1.0% or more of C. On the other hand, if C is contained in an amount exceeding 3.5%, the amount of carbide precipitated becomes excessive, and the target offensive property increases. From this point of view, C is limited to a range of 1.0 to 3.5%.

Si：2.0～3.5%

Si is an element that acts as a deacidification agent and improves sinterability. In order to obtain such an effect, in the present invention, Si needs to be contained by 2.0% or more. On the other hand, if Si is contained in an amount exceeding 3.5%, the hardness of the powder increases, and the moldability decreases. Therefore, Si is limited to a range of 2.0 to 3.5%.

P：0.3～1.0%

P forms a liquid phase (Fe-P-C) together with C during sintering in the present invention, contributing to increase the density of the sintered body. In order to obtain such an effect, it is necessary to contain 0.3% or more of P. When P is less than 0.3%, a sufficient liquid phase cannot be formed, and a desired density cannot be secured. On the other hand, if P is contained in an amount exceeding 1.0%, the amount of liquid phase produced becomes too large, and it becomes difficult to maintain the shape during sintering. Therefore, P is limited to the range of 0.3 to 1.0%.

Cr：15～32%

Cr is an element that is solid-dissolved to improve the heat resistance and corrosion resistance of the substrate. In addition, Cr is precipitated as carbide in combination with C, contributing to improvement of wear resistance. In order to obtain such an effect, it is necessary to contain 15% or more of Cr. If Cr is less than 15%, the amount of carbide precipitation decreases, and the desired wear resistance cannot be ensured. On the other hand, if Cr is contained in a large amount exceeding 32%, the hardness of the powder increases, and the moldability decreases. From this point of view, Cr is limited to a range of 15 to 32%.

Ni：14～25%

Ni is an element that strengthens a matrix by solid solution and contributes to increase high-temperature strength by austenitizing the matrix. In order to obtain such an effect, it is necessary to contain 14% or more of Ni. When Ni is less than 14%, the high-temperature strength is insufficient. On the other hand, even if Ni is contained in an amount exceeding 25%, the high-temperature strength cannot be expected to be significantly increased, and therefore, this is economically disadvantageous. In this respect, Ni is limited to a range of 14 to 25%.

Mo：1.5～4.9%

Mo is an element that is solid-dissolved to improve the heat resistance and corrosion resistance of the matrix, and is combined with C to precipitate as carbide, contributing to improvement of wear resistance. In order to obtain such an effect, it is necessary to contain 1.5% or more of Mo. When Mo is less than 1.5%, the effect of improving heat resistance and corrosion resistance is insufficient. On the other hand, in the case of a liquid,even if Mo is contained in a large amount exceeding 4.9%, the effect is saturated, and the effect matching the content cannot be expected, which is economically disadvantageous. In this respect, Mo is limited to a range of 1.5 to 4.9%. Mo includes solid lubricant particles MoS as required for improving lubricity₂The form of (1) is added.

Nb：0.5～4.0%

Nb is an element that generates fine carbides and improves wear resistance. In order to obtain such an effect, 0.5% or more of Nb needs to be contained. On the other hand, if Nb is contained in an amount exceeding 4.0%, the hardness of the powder increases, and the moldability decreases. Nb has a stronger affinity for C than Cr, and precipitates Nb carbides before Cr carbides are formed. Thus, the consumption of Cr in the matrix phase is avoided, and the corrosion resistance of the matrix is prevented from being lowered. In this respect, Nb is limited to a range of 0.5 to 4.0%.

W：0.5～6.1%

W is an element that generates fine carbides and improves wear resistance, like Nb. W also has a stronger affinity for C than Cr, like Nb, and precipitates carbide of W before Cr carbide is formed. Thus, the consumption of Cr in the matrix phase is avoided, and the corrosion resistance of the matrix is prevented from being lowered. In order to obtain such an effect, it is necessary to contain 0.5% or more of W. On the other hand, if the content exceeds 6.1%, the hardness of the powder increases, and the moldability decreases. In this respect, W is limited to a range of 0.5% to 6.1%. W includes solid lubricant particles WS as required for improving lubricity₂The form of (1) is added.

The above-mentioned component is a basic component, and in addition to the basic component, may further contain Mn: 3.2% or less and S: 2.0% or less, or S: 2.0% or less, Cu: 1.0-3.5% of a selective element.

Mn: 3.2% or less

Mn is mainly MnS as solid lubricant particles, and is preferably added in an amount of 0.19% or more as necessary for improving lubricity and machinability. On the other hand, if the solid lubricant particles are contained in a large amount exceeding 3.2% in terms of Mn, the strength of the sintered alloy material is lowered. From this point of view, Mn is limited to a range of 3.2% or less. The Mn is preferably 0.6 to 1.9%.

S: 2.0% or less

S is mainly MnS, MoS as solid lubricant particles₂、WS₂In order to improve lubricity and machinability, it is preferable to add 0.11% or more in terms of S as necessary. If the solid lubricant particles are contained in a large amount exceeding 2.0% in terms of S, the strength of the sintered alloy material is lowered. In this respect, S is limited to a range of 2.0% or less. Preferably, S is 0.4 to 1.1%.

Cu：1.0～3.5%

The inclusion of Cu strengthens the matrix by solid solution, and contributes to improvement of wear resistance. Therefore, a predetermined amount of Cu is preferably contained as necessary. In order to obtain such an effect, it is necessary to contain 1.0% or more. On the other hand, if the content exceeds 3.5%, free Cu precipitates and the wear resistance is lowered. From this point of view, Cu is preferably limited to a range of 1.0 to 3.5%.

The balance other than the above components is composed of Fe and inevitable impurities.

The heat-resistant sintered alloy material of the invention is the following sintered alloy material: in addition to the above composition, the composition has a structure in which the matrix is an austenite phase, and in which carbides are precipitated or solid lubricant particles are further dispersed, and has a hardness of 55 to 75 in terms of Rockwell hardness HRA and a density of 7.2g/cm³The above.

When the composition is in the above-mentioned range of Cr, Ni and the like, the matrix forms an austenite phase after sintering, and carbide such as Cr carbide is finely dispersed in the matrix. The carbide-forming particle size dispersed in the matrix is 1μm is 40 or moreμFine carbides of m or less. This increases the hardness by HRA of 55 to 75, and is expected to improve the wear resistance.

In the heat-resistant sintered alloy material of the present invention, a liquid phase is formed during sintering, and the amount of pores is set to an appropriate range to increase the density and further improve the wear resistance. It should be noted that the holesThe ratio is preferably 7% or less in terms of area ratio. If the porosity exceeds 7% by area, the desired wear resistance cannot be ensured. The density is reduced to 7.2g/cm by reducing the porosity³Above, preferably up to 7.4g/cm³The above.

Next, a preferred method for producing the heat-resistant sintered alloy material of the present invention will be described.

The heat-resistant sintered alloy material of the present invention is a powder compact-made sintered body produced by powder compact forming-sintering, which has the following advantages: a component having a desired dimensional shape can be secured with high accuracy with a small amount of machining.

Specifically, an additive powder such as a solid lubricant powder or a machinability improving particle powder is added to a raw material powder or further added thereto, and the mixture is mixed and kneaded to form a mixed powder. Then, the obtained mixed powder is put into a die and is subjected to powder compaction by press compaction or the like to form a powder compact having a predetermined size and shape. Then, the obtained green compact is subjected to sintering treatment to form a sintered body (sintered alloy material). The raw material powder is obtained by blending graphite powder, alloying element powder, Fe — P alloy powder, and the like as needed with iron alloy powder or iron-based powder further containing iron powder so that the above-described desired composition is achieved in mass% with respect to the total amount of the blended powder.

When an alloy element powder containing an alloy element such as Cr, Mo, or P as a simple substance is mixed with an iron powder, homogenization of the alloy element is insufficient, and therefore, alloying with the iron powder in advance to form an iron alloy powder is also effective in homogenization of the structure. There is no problem even if a part of the alloying elements such as Ni is mixed as the alloying element powder. Since the iron alloy powder is significantly solidified when C is alloyed with the iron alloy powder, it is not necessary to alloy in advance, and a predetermined amount of the graphite powder is preferably mixed.

As the solid lubricant powder, manganese sulfide (MnS) and molybdenum disulfide (MoS) were used₂) Tungsten disulfide (WS)₂) Etc. ofConventional lubricant particle powders may be used. When the solid lubricant powder is blended, two or more kinds may be mixed, and the blending amount of the solid lubricant powder is preferably 0.3 to 5% in total in mass% based on the total amount of the blended powder. More preferably, the concentration is 1 to 3%.

Then, the mixed powder is put into a mold, and a green compact having a predetermined shape is formed by press molding. The density of the green compact is preferably 6.0g/cm³The above.

The obtained green compact was charged into a sintering furnace to prepare a sintered body. The sintering treatment is liquid phase sintering that generates a part of liquid phase. By forming liquid phase sintering, the liquid phase is impregnated into a part of the pores, and the pores are reduced to make the density 7.2g/cm³The above.

The sintering temperature is preferably 1100-1200 ℃. When the sintering temperature is lower than 1100 ℃, liquid phase sintering is insufficient, and a desired density cannot be secured. On the other hand, when the temperature exceeds 1200 ℃ and reaches a high temperature, carbide becomes coarse.

The atmosphere of the sintering treatment is preferably a non-oxidizing atmosphere such as a vacuum atmosphere, a mixed gas atmosphere of hydrogen and nitrogen, or an ammonia decomposition gas (AX) atmosphere.

The present invention will be further described with reference to examples.