A nickel-iron alloy for automotive turbine impellers and its preparation method

Abstract

A nickel-iron alloy for automotive turbine impellers comprises, by mass percentage: Cr 12–22%, Ni 37–50%, C 0.1–0.322%, W 4.5–8.5%, Mo 0.5–2.8%, Al 1.5–3.5%, B 0.06–0.25%, Si ≤0.5%, Mn ≤0.5%, Tb ≤0.15%, Ho ≤0.12%, Gd ≤0.2%, and the balance Fe. This nickel-iron alloy exhibits excellent wear resistance at 1000℃, high hardness at room temperature, and long service life. It can operate stably at 1000℃ for extended periods, significantly improving work efficiency.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to an iron-nickel alloy for automotive turbine impellers and its preparation method. Background Technology

[0002] In automotive technology, the turbocharger, as a crucial component, primarily increases the engine's intake air volume. The turbine blades are a key part of the turbocharger, constantly needing to withstand the friction and wear caused by high temperatures and high-speed airflow. Simultaneously, during high-speed rotation, the turbine impeller easily generates friction with bearings and other components, leading to localized high temperatures. This friction easily causes wear on the turbine impeller material, and high temperatures exacerbate this frictional damage, thus reducing the material's lifespan. Therefore, turbine impeller materials need to possess not only high temperature resistance but also high hardness and high-temperature wear resistance.

[0003] Currently, materials commonly used in automotive turbine impellers include nickel alloys, titanium alloys, and stainless steel. However, the hardness and wear resistance of these materials at high temperatures (1000℃) need further improvement. Therefore, it is essential to research an iron-nickel alloy for automotive turbine impellers and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing an iron-nickel alloy for automotive turbine impellers and its preparation method, thereby at least partially solving the problems of the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] On one hand, an iron-nickel alloy for automotive turbine impellers comprises, by mass percentage: Cr 12-22%, Ni 37-50%, C 0.1-0.322%, W 4.5-8.5%, Mo 0.5-2.8%, Al 1.5-3.5%, B 0.06-0.25%, Si≤0.5%, Mn≤0.5%, Tb≤0.15%, Ho≤0.12%, Gd≤0.2%, with the balance being Fe.

[0007] In a further embodiment, the iron-nickel alloy used for the automotive turbine impeller comprises, by mass percentage: Cr 15.3–16.2%, Ni 43.4–45%, C 0.1–0.322%, W 7.5–8.5%, Mo 1.6–2.8%, Al 2.6–3%, B 0.06–0.1%, Si 0.3–0.5%, Mn 0.3–0.5%, Tb 0.08–0.12%, Ho 0.1–0.12%, Gd 0.16–0.2%, with the balance being Fe.

[0008] Preferably, the iron-nickel alloy for the automotive turbine impeller comprises, by mass percentage: Cr 15.6–16.2%, Ni 43.4–45%, C 0.1–0.322%, W 8.4–8.5%, Mo 2.5–2.8%, Al 3%, B 0.06–0.1%, Si 0.45–0.5%, Mn 0.45–0.5%, Tb 0.1–0.12%, Ho 0.1–0.12%, Gd 0.18–0.2%, with the balance being Fe.

[0009] On the other hand, the above-mentioned method for preparing iron-nickel alloy for automotive turbine impellers includes the following steps:

[0010] Step 1: Smelting

[0011] According to the above component ratio, nickel plate, steel, low carbon ferrochrome, high carbon ferrochrome, ferrotungsten, molybdenum powder, aluminum lime, boron powder, terbium, holmium, and gadolinium are refined, and then silicon and manganese are added and kept at a constant temperature to obtain the casting liquid.

[0012] Step Two: Casting

[0013] The casting liquid is poured in to obtain a cast part;

[0014] Step 3: Heat Treatment

[0015] The cast part is heated to 1150-1170℃ and then held at this temperature under high pressure. After the holding period, it is cooled to room temperature to obtain the first preform.

[0016] Step 4: Solution Treatment

[0017] The first preform is subjected to solution treatment to obtain the second preform;

[0018] Step 5: Time-sensitive processing

[0019] The second preform is subjected to aging treatment to obtain an iron-nickel alloy for automotive turbine impellers.

[0020] In a further embodiment, in step one, the refining temperature is 1620–1640°C, and the refining time is 10–15 min; the heat preservation temperature is 1620–1640°C, and the heat preservation time is 8–10 min.

[0021] In a further embodiment, in step three, the heating rate is ≤10℃ / min; the holding temperature is 1150~1170℃, the holding time is 5~6h; and the high pressure applied during the heating and holding process is 100~120Mpa.

[0022] In a further embodiment, in step three, the cooling to room temperature is achieved by furnace-side cooling, and the cooling rate to room temperature is ≤30℃ / min.

[0023] In a further embodiment, step four, the solution treatment step, is as follows:

[0024] The first preform is placed in a heating furnace and heated to 1150-1180°C at a heating rate of 5-10°C / min. It is then held at this temperature for 3-4 hours and then air-cooled to room temperature to obtain the second preform.

[0025] Preferably, the heating rate of the solution treatment is 10℃ / min for temperatures below 1000℃ and 5℃ / min for temperatures above 1000℃.

[0026] In a further proposed solution, step five, the timeliness processing steps, are as follows:

[0027] The second preform is placed in a heat treatment furnace and heated to 850-870°C at a heating rate of ≤10°C / min. It is then held at this temperature for 7-8 hours and air-cooled to room temperature to obtain the third preform.

[0028] Preferably, in step five, the temperature of the heat treatment furnace is ≤100℃ before the second preform is placed into the heat treatment furnace.

[0029] On the other hand, an automotive turbine impeller is made from the aforementioned automotive turbine impeller made of an iron-nickel alloy.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention provides an iron-nickel alloy for automotive turbine impellers. Through the strengthening effect of five main elements (nickel, iron, chromium, tungsten, and molybdenum), the grain boundary strengthening effect of trace elements (carbon and boron), and the purification effect of rare earth elements, the iron-nickel alloy for automotive turbine impellers has excellent wear resistance at 1000℃, high hardness at room temperature, long service life, and can operate stably at 1000℃ for a long time, greatly improving work efficiency.

[0032] 2. The iron-nickel alloy for automotive turbine impellers of the present invention incorporates rare earth elements such as terbium, holmium, and gadolinium. Terbium, holmium, and gadolinium work synergistically to enhance grain boundary bonding and improve the high-temperature wear resistance and hardness of the alloy.

[0033] 3. The iron-nickel alloy used in the automotive turbine impeller of this invention exhibits a high-temperature wear of only 0.007 mm at 1000℃. 3 Under the same conditions, the alloy is 0.025mm thicker. 3 It has one-third the capacity and excellent high-temperature wear resistance. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope (SEM) image of the as-cast part prepared in Example 1 of this invention.

[0035] Figure 2 This is a scanning electron microscope (SEM) micrograph (1000x) of the iron-nickel alloy for automotive turbine impellers prepared in Example 1 of this invention;

[0036] Figure 3 This is a scanning electron microscope (SEM) image (100x) of the iron-nickel alloy for automotive turbine impellers prepared in Example 1 of this invention. Detailed Implementation

[0037] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following description is merely an exemplary illustration of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0038] Turbine blades are a key component of turbochargers, constantly subjected to frictional wear caused by high temperatures and high-speed airflow. Simultaneously, during high-speed rotation, the turbine impeller easily rubs against bearings and other components, leading to localized high temperatures. This friction easily causes wear on the turbine impeller material, and high temperatures exacerbate this wear, thus reducing the material's lifespan. Therefore, turbine impeller materials need to possess not only high temperature resistance but also high hardness and high-temperature wear resistance. However, current turbine impeller materials cannot meet the requirements for long-term stable use under 1000℃ conditions.

[0039] This invention employs a process of smelting and casting, special heat treatment, solution treatment, and aging treatment to prepare iron-nickel alloy for automotive turbine impellers. Through reasonable design, the iron-nickel alloy for automotive turbine impellers can operate stably for a long time at 1000℃, greatly improving working efficiency. Its excellent wear resistance at high temperatures extends the service life of the material, resulting in significant cost reduction and profit gains in actual production.

[0040] To address the aforementioned problems, embodiments of the present invention provide an iron-nickel alloy for automotive turbine impellers, comprising the following components by mass percentage: Cr 12–22%, Ni 37–50%, C 0.1–0.322%, W 4.5–8.5%, Mo 0.5–2.8%, Al 1.5–3.5%, B 0.06–0.25%, Si ≤0.5%, Mn ≤0.5%, Tb ≤0.15%, Ho ≤0.12%, Gd ≤0.2%, and the balance Fe.

[0041] In a further embodiment, the iron-nickel alloy used for the automotive turbine impeller comprises, by mass percentage: Cr 15.3–16.2%, Ni 43.4–45%, C 0.1–0.322%, W 7.5–8.5%, Mo 1.6–2.8%, Al 2.6–3%, B 0.06–0.1%, Si 0.3–0.5%, Mn 0.3–0.5%, Tb 0.08–0.12%, Ho 0.1–0.12%, Gd 0.16–0.2%, and the balance Fe.

[0042] Preferably, the iron-nickel alloy for the automotive turbine impeller comprises, by mass percentage: Cr 15.6–16.2%, Ni 43.4–45%, C 0.1–0.322%, W 8.4–8.5%, Mo 2.5–2.8%, Al 3%, B 0.06–0.1%, Si 0.45–0.5%, Mn 0.45–0.5%, Tb 0.1–0.12%, Ho 0.1–0.12%, Gd 0.18–0.2%, and the balance Fe.

[0043] The iron-nickel alloy of this invention uses Ni to form a stable austenitic matrix, ensuring the stability of the alloy structure; other refractory metals mainly play a solid solution strengthening role, improving the high-temperature strength of the alloy; the introduction of rare earth elements such as terbium, holmium, and gadolinium is beneficial to enhancing the grain boundary bonding force and improving the high-temperature wear resistance of the alloy, enabling it to operate stably for a long time at a working temperature of 1000℃.

[0044] This invention also provides a method for preparing an iron-nickel alloy for automotive turbine impellers, comprising the following steps:

[0045] Step 1: Smelting

[0046] According to the above component ratio, nickel plate, steel, low carbon ferrochrome, high carbon ferrochrome, ferrotungsten, molybdenum powder, aluminum lime, boron powder, terbium, holmium, and gadolinium are refined, and then silicon and manganese are added and kept at a constant temperature to obtain the casting liquid.

[0047] Step Two: Casting

[0048] The casting liquid is poured in to obtain a cast part;

[0049] Step 3: Heat Treatment

[0050] The cast part is heated to 1150-1170℃ and then held at this temperature under high pressure. After the holding period, it is cooled to room temperature to obtain the first preform.

[0051] Step 4: Solution Treatment

[0052] The first preform is subjected to solution treatment to obtain the second preform;

[0053] Step 5: Time-sensitive processing

[0054] The second preform is subjected to aging treatment to obtain an iron-nickel alloy for automotive turbine impellers.

[0055] In a further embodiment, in step one, the refining temperature is 1620–1640°C, and the refining time is 10–15 min; the heat preservation temperature is 1620–1640°C, and the heat preservation time is 8–10 min.

[0056] In a further embodiment, in step three, the heating rate is ≤10℃ / min; the holding temperature is 1150~1170℃, the holding time is 5~6h; and the high pressure applied during the heating and holding process is 100~120Mpa.

[0057] In this invention, after casting an iron-nickel alloy, heat treatment is performed first, followed by solution treatment and aging treatment. High pressure is applied during the heating and holding processes of the heat treatment. Controlling the high pressure conditions helps to reduce the porosity of the component, increase its density, and promote the homogenization of the microstructure, thereby improving the hardness and high-temperature wear resistance of the material.

[0058] In a further embodiment, in step three, the cooling to room temperature is achieved by furnace-side cooling, and the cooling rate to room temperature is ≤30℃ / min.

[0059] In a further embodiment, step four, the solution treatment step, is as follows:

[0060] The first preform is placed in a heating furnace and heated to 1150-1180°C at a heating rate of 5-10°C / min. It is then held at this temperature for 3-4 hours and then air-cooled to room temperature to obtain the second preform.

[0061] Preferably, the heating rate of the solution treatment is 10℃ / min for temperatures below 1000℃ and 5℃ / min for temperatures above 1000℃.

[0062] In the solution treatment process, the present invention selects different heating rates at different temperature ranges. Compared with heating at the same rate, the present invention is more conducive to forming a uniform structure and increasing the amount of strengthening phase precipitated.

[0063] In a further proposed solution, step five, the timeliness processing steps, are as follows:

[0064] The second preform is placed in a heat treatment furnace and heated to 850-870°C at a heating rate of ≤10°C / min. It is then held at this temperature for 7-8 hours and air-cooled to room temperature to obtain the third preform.

[0065] Preferably, in step five, before the second preform is placed into the heat treatment furnace, the temperature of the heat treatment furnace is ≤100℃. Controlling the temperature of the heat treatment furnace is beneficial for achieving uniform microstructure, increasing the amount of reinforcing phase precipitated, and improving material properties.

[0066] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0067] Examples 1-5 and Comparative Examples 1-6

[0068] An iron-nickel alloy for automotive turbine impellers, the composition of which is shown in Table 1 below, is prepared by the following steps:

[0069] Step 1: Smelting

[0070] According to the composition ratio shown in Table 1, nickel plate, steel, low carbon ferrochrome, high carbon ferrochrome, ferrotungsten, molybdenum powder, aluminum lime, boron powder, terbium, holmium and gadolinium are refined for 15 minutes to melt them. Then silicon and manganese are added and kept at 1640℃ for 10 minutes to obtain casting liquid.

[0071] Step Two: Casting

[0072] The temperature of the casting liquid is controlled at 1640℃. The casting liquid is poured into the ingot mold and cooled to room temperature to obtain the cast part.

[0073] Step 3: Heat Treatment

[0074] The cast part was heated to 1170℃ at a heating rate of 10℃ / min, while a high pressure of 120MPa was applied simultaneously during the heating process. After the temperature stabilized, the cast part was kept at 1170℃ and 120MPa for 4 hours. Then, the part was cooled in the furnace at a rate not exceeding 30℃ / min until it reached room temperature, at which point the first preform was obtained.

[0075] Step 4: Solution Treatment

[0076] The first preform is placed in a heating furnace and heated to 1000°C at a heating rate of 10°C / min, and then heated to 1180°C at a heating rate of 5°C / min. After the temperature stabilizes, it is kept at this temperature for 4 hours and then air-cooled to room temperature to obtain the second preform.

[0077] Step 5: Time-sensitive processing

[0078] The second preform is placed in a heat treatment furnace (the initial temperature of the heat treatment furnace is 100℃), and heated to 870℃ at a heating rate of 10℃ / min. After the temperature stabilizes, it is held at this temperature for 8 hours, and then air-cooled to room temperature to obtain the iron-nickel alloy for automotive turbine impellers.

[0079] Table 1

[0080]

[0081]

[0082] The difference between Comparative Example 7 and Example 2 is that no high pressure is applied during the heating process in the heat treatment section of this comparative example.

[0083] The difference between Comparative Example 8 and Example 2 is that no high pressure is applied during the heat treatment process in this comparative example.

[0084] The difference between Comparative Example 9 and Example 2 is that no high pressure is applied during the heating and holding processes in the heat treatment section of this comparative example.

[0085] The difference between Comparative Example 10 and Example 2 is that this comparative example does not have a heat treatment process, that is, the cast parts are directly subjected to solution treatment.

[0086] The difference between Comparative Example 11 and Example 2 is that the heating rate in the solution treatment section of this comparative example is 10°C / min.

[0087] The difference between Comparative Example 12 and Example 2 is that the heating rate in the solution treatment section of this comparative example is 5°C / min.

[0088] Experimental Example 1

[0089] The microstructure of the cast parts and the iron-nickel alloy for automotive turbine impellers prepared in Example 1 was analyzed using field emission scanning electron microscopy. The results are as follows: Figures 1 to 3 As shown.

[0090] As shown in the figure Figure 1 The microstructure of the cast part Figure 2 and Figure 3The microstructure of the iron-nickel alloy used in automotive turbine impellers is shown. Compared to cast parts, the iron-nickel alloy used in automotive turbine impellers has a more uniform microstructure, resulting in improved alloy strength and overall performance. The precipitated phases in the microstructure of the iron-nickel alloy used in automotive turbine impellers are mainly strengthening phases and secondary carbides M6C. Both precipitated phases are large in size and abundant in quantity, significantly increasing the alloy's hardness and thus enhancing its high-temperature wear resistance. The addition of rare earth elements also improves the alloy's wear resistance, greatly extending the service life of the iron-nickel alloy at 1000℃ while also achieving cost reduction and profit enhancement.

[0091] Experimental Example 2

[0092] The following tests were conducted on the iron-nickel alloys for automotive turbine impellers prepared in the above embodiments and comparative examples, with ZG40Cr25Ni20 heat-resistant steel as a control.

[0093] 1. Room temperature hardness properties

[0094] According to standard GB / T231.1-2009, room temperature hardness tests were conducted using an HBRV-187.5 electric Briović hardness tester.

[0095] 2. High-temperature wear performance

[0096] High-temperature friction and wear tests were conducted using a CSM brand THT01-04015 high-temperature friction testing machine, with silicon nitride ceramic balls as the abrasive material. Temperature 1000℃, load 25N, frequency 5Hz, linear reciprocating high-temperature friction at 1000℃ for 20 minutes under atmospheric conditions.

[0097] The experimental results are shown in Table 2.

[0098] Table 2

[0099] Example 1 352 0.070 Example 2 363 0.050 Example 3 345 0.080 Example 4 359 0.065 Example 5 348 0.082 Comparative Example 1 315 0.184 Comparative Example 2 313 0.186 Comparative Example 3 311 0.287 Comparative Example 4 314 0.276 Comparative Example 5 282 0.298 Comparative Example 6 281 0.299 Comparative Example 7 314 0.186 Comparative Example 8 302 0.194 Comparative Example 9 294 0.260 Comparative Example 10 290 0.330 Comparative Example 11 326 0.166 Comparative Example 12 329 0.160 ZG40Cr25Ni20 heat-resistant steel 165 0.250

[0100] As shown in the table, the room temperature hardness of ZG40Cr25Ni20 heat-resistant steel is 165 HBS, while the room temperature hardness of the iron-nickel alloy prepared by this invention exceeds 340 HBS, more than twice that of ZG40Cr25Ni20 heat-resistant steel, indicating a significant increase in hardness. The results of Comparative Examples 1-6 show that terbium, holmium, and gadolinium have a synergistic effect, contributing to improving the room temperature hardness of the alloy; the room temperature hardness is highest when all three elements are present simultaneously. The results of Comparative Examples 7-10 show that heat treatment before solution treatment and controlling the heat treatment conditions help improve the hardness of the alloy.

[0101] The wear rate results show that the wear rate of ZG40Cr25Ni20 heat-resistant steel is 0.25 mm. 3The wear rate of the iron-nickel alloy obtained by this invention is 0.05-0.08 mm. 3 The wear rate of ZG40Cr25Ni20 heat-resistant steel is more than three times that of iron-nickel alloys. Therefore, the iron-nickel alloy prepared by this invention has significantly superior wear resistance at high temperatures and a much longer service life. Since the improvement of hardness directly affects the high-temperature wear resistance of the alloy, the addition of the three rare earth elements has a synergistic effect, which is beneficial to improving the hardness of the alloy and, correspondingly, also beneficial to improving the high-temperature wear resistance of the alloy.

[0102] The results of Comparative Examples 7-10 show that only by applying high pressure simultaneously during the heating and holding process, followed by solution treatment, can the room temperature hardness and high temperature wear resistance of the alloy be greatly improved.

[0103] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A nickel-iron alloy for automotive turbine impellers, characterized in that, By mass percentage, it contains the following components: Cr 12-22%, Ni 37-50%, C 0.1-0.322%, W 4.5-8.5%, Mo 0.5-2.8%, Al 1.5-3.5%, B 0.06-0.25%, Si≤0.5%, Mn≤0.5%, Tb≥0.08 and≤0.15%, Ho≥0.1 and≤0.12%, Gd≥0.16 and≤0.2%, with the balance being Fe.

2. The iron-nickel alloy for automotive turbine impellers according to claim 1, characterized in that, By mass percentage, it contains the following components: Cr 15.3–16.2%, Ni 43.4–45%, C 0.1–0.32%, W 7.5–8.5%, Mo 1.6–2.8%, Al 2.6–3%, B 0.06–0.1%, Si 0.3–0.5%, Mn 0.3–0.5%, Tb 0.08–0.12%, Ho 0.1–0.12%, Gd 0.16–0.2%, with the balance being Fe.

3. The iron-nickel alloy for automotive turbine impellers according to claim 2, characterized in that, By mass percentage, it contains the following components: Cr 15.6–16.2%, Ni 43.4–45%, C 0.1–0.32%, W 8.4–8.5%, Mo 2.5–2.8%, Al 3%, B 0.06–0.1%, Si 0.45–0.5%, Mn 0.45–0.5%, Tb 0.1–0.12%, Ho 0.1–0.12%, Gd 0.18–0.2%, with the balance being Fe.

4. The method for preparing the iron-nickel alloy for automotive turbine impellers according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Smelting The nickel plate, steel, low-carbon ferrochrome, high-carbon ferrochrome, ferrotungsten, molybdenum powder, aluminum lime, boron powder, terbium, holmium, and gadolinium are refined, and then silicon and manganese are added. The mixture is kept at a constant temperature to obtain the casting liquid. Step Two: Casting The casting liquid is poured in to obtain a cast part; Step 3: Heat Treatment The cast part is heated to 1150-1170℃ and then held at this temperature under high pressure. After the holding period, it is cooled to room temperature to obtain the first preform. Step 4: Solution Treatment The first preform is subjected to solution treatment to obtain the second preform; Step 5: Time-sensitive processing The second preform is subjected to aging treatment to obtain an iron-nickel alloy for automotive turbine impellers.

5. The preparation method according to claim 4, characterized in that, In step three, the heating rate is ≤10℃ / min; the holding temperature is 1150~1170℃; the holding time is 5~6h; and the high pressure applied during the heating and holding processes is 100~120Mpa.

6. The preparation method according to claim 4, characterized in that, The solution treatment steps are as follows: The first preform is placed in a heating furnace and heated to 1150-1180°C at a heating rate of 5-10°C / min. It is then held at this temperature for 3-4 hours and then air-cooled to room temperature to obtain the second preform.

7. The preparation method according to claim 6, characterized in that, The heating rate for the solution treatment is 10℃ / min for temperatures below 1000℃ and 5℃ / min for temperatures above 1000℃.

8. The preparation method according to claim 4, characterized in that, In step five, the timeliness processing steps are as follows: The second preform is placed in a heat treatment furnace and heated to 850-870°C at a heating rate of ≤10°C / min. It is then held at this temperature for 7-8 hours and air-cooled to room temperature to obtain the third preform.

9. The preparation method according to claim 8, characterized in that, Before the second preform is placed into the heat treatment furnace, the temperature of the heat treatment furnace is ≤100℃.

10. An automotive turbine impeller, characterized in that, It is prepared from the iron-nickel alloy for automobile turbine impellers as described in any one of claims 1 to 3.

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