A Fe-based superalloy powder and its application

Abstract

The present invention discloses an iron-based high-temperature alloy powder, the chemical composition and mass percentage of which are as follows: 0.4-0.6% C, 18.0-20.0% Cr, 14.0-16.0% Ni, 10.5-12.0% Mo, 10.5-12.0% Nb, 0.5-1.0% Si, 1.5-2.0% S; the balance is Fe and unavoidable impurities. The iron-based high-temperature alloy powder of the present invention comprehensively considers the performance requirements of high-temperature resistance, wear resistance, and fatigue resistance, and takes into account the interactions between the various chemical elements, enabling it to be used for a long time at 1000°C. The iron-based high-temperature alloy powder of the present invention is formed into a coating on the surface of a part through laser cladding, which improves the workpiece's high-temperature resistance, wear resistance, and fatigue resistance, and its service life is increased by more than three times. At the same time, the present invention also discloses the application scenarios and usage methods of the iron-based high-temperature alloy powder.

Description

Technical Field

[0001] The present invention relates to the field of metal materials, and in particular to an iron-based high-temperature alloy powder and applications thereof. Background Art

[0002] Superalloys are a type of alloy material that can operate for extended periods at temperatures exceeding 600°C and under certain stresses. They possess comprehensive properties, including high high-temperature strength, excellent high-temperature oxidation resistance, and good fatigue performance. Therefore, they are widely used in aviation, aerospace, petroleum, chemical engineering, and shipbuilding.

[0003] According to the classification of matrix elements, high-temperature alloys can generally be divided into iron-based, nickel-based, cobalt-based, etc. The operating temperature of iron-based high-temperature alloys is generally below 800°C. For heat-resistant components used at higher temperatures, high-temperature alloys with nickel-based, cobalt-based or refractory metals as the matrix are used. However, high-temperature alloy materials with nickel-based, cobalt-based or refractory metals as the matrix are relatively more expensive and can often only be used in high-end products such as aircraft engines and gas turbine hot end components. Although general industrial products also have the need to be used at high temperatures, due to the high cost, they often can only use ordinary iron-based high-temperature alloy materials.

[0004] Therefore, it is extremely important to conduct relevant research and development on iron-based high-temperature alloy materials used at higher temperatures (1000°C).

[0005] During the hot-rolled piercing process of seamless steel pipes, the piercing machine head is subjected to high temperature (1000°C), complex rolling force and friction, and is also subjected to hot and cold cycles. It is very easy to produce defects such as nose collapse, meat loss, steel sticking, cracking, etc., and its service life is relatively low. Especially when rolling high-alloy steel pipes, one piercing machine head can only roll 4-5 steel pipes, which greatly reduces the company's production efficiency and increases production costs. Therefore, it is necessary to design a surface strengthening scheme based on the working conditions of the piercing machine head to extend its service life. At present, although many researchers have tried, according to feedback from steel pipe factories, there is still a lack of a suitable strengthening process. Either the service life has not been significantly improved, or the production cost is too high. Summary of the Invention

[0006] The present invention aims to provide an iron-based superalloy powder that comprehensively considers the performance requirements of high-temperature resistance, wear resistance, and fatigue resistance, as well as the interactions between various chemical elements, enabling long-term use at 1000°C. The present invention also provides applications for the iron-based superalloy powder.

[0007] The invention discloses an iron-based high-temperature alloy powder, the chemical composition and mass percentage of which are: 0.4-0.6% C, 18.0-20.0% Cr, 14.0-16.0% Ni, 10.5-12.0% Mo, 10.5-12.0% Nb, 0.5-1.0% Si, 1.5-2.0% S; the balance is Fe and inevitable impurities.

[0008] Furthermore, the mass percentage of Fe element is ≥39.0%; the mass percentage ratio of Mo element to Nb element is 1:1; and the mass percentage ratio of Ni element to (Mo+Nb) element is 1:1.5.

[0009] Furthermore, the particle size of the iron-based high-temperature alloy powder ranges from 75 to 180 μm.

[0010] The principles and effects of the iron-based high-temperature alloy powder material of the present invention are as follows:

[0011] 1. Adding 18.0-20.0% Cr to the iron-based superalloy powder primarily enhances its high-temperature oxidation resistance. The oxidation resistance of iron-based superalloys increases with increasing Cr content. Extensive testing has shown that when the Cr content reaches 18.0-20.0%, the alloy can form a stable oxide film at 1000°C without scaling. Furthermore, the addition of Cr also promotes solid solution strengthening, thereby increasing the alloy's strength.

[0012] Second, adding 14.0-16.0% Ni to the iron-based superalloy powder ensures good room-temperature and high-temperature plasticity, thus preventing cracking during laser cladding. It also enhances the stability of the γ' phase at high temperatures, thereby improving its high-temperature strength. Extensive experimental research has found that the optimal strengthening effect is achieved only when the Ni content reaches 14.0% or above.

[0013] 3. 10.5-12.0% Mo and 10.5-12.0% Nb are added to the iron-based high-temperature alloy powder, mainly to improve its high-temperature strength and wear resistance at high temperatures. The addition of Mo and Nb not only plays a role in solid solution strengthening, but also can form intermetallic compounds, forming precipitation strengthening. Moreover, Mo and Nb elements themselves have high melting points, and the intermetallic compounds formed with other elements in the alloy have high high-temperature strength. In addition, the addition of Nb will also refine the grains, improving the strength while also improving the plasticity of the alloy. Nb will also form carbides with C, thereby improving the wear resistance of the alloy. In addition, after a large number of experimental studies, it was found that the best strengthening effect can be achieved when the ratio of Mo and Nb elements is 1:1.

[0014] 4. To obtain good thermal fatigue resistance, iron-based high-temperature alloy powders need to achieve the best match between plasticity and strength. Based on this, when the mass percentage ratio of Ni and (Mo+Nb) elements in the iron-based high-temperature alloy powder is 1:1.5, it can ensure that the alloy has good high-temperature strength while also having good thermal fatigue resistance.

[0015] 5. The iron-based high-temperature alloy powder contains 0.5-1.0% Si element, which mainly plays the role of deoxidation and slag formation. It is also considered from the perspective of laser cladding formability. The addition of silicon can also improve the hardness and oxidation resistance of the alloy.

[0016] 6. The addition of 1.5-2.0% S to the iron-based superalloy powder, in stark contrast to the traditional concept of S as an impurity element, primarily allows it to react with Mo in situ at high temperatures to form the MoS2 lubricating phase. Molybdenum disulfide has excellent lubricity, and adding a certain amount to the alloy can significantly improve its wear resistance. Therefore, the addition of 1.5-2.0% S enhances the wear resistance of the iron-based superalloy at high temperatures.

[0017] 7. Iron-based superalloy powders must contain at least 39.0% iron, primarily to reduce costs. Furthermore, only when the matrix element reaches a certain concentration can the solid solution strengthening effects of other alloying elements be fully realized. Therefore, the Fe content in the iron-based superalloy powder must be ≥ 39.0% by weight.

[0018] In summary, the chemical composition design of the iron-based high-temperature alloy powder of the present invention comprehensively considers the performance requirements of high temperature resistance, wear resistance, and fatigue resistance, and takes into account the interactions between various chemical elements, and is the best combination obtained through a large number of experimental studies and demonstrations.

[0019] In addition, the particle size range of the iron-based high-temperature alloy powder of the present invention is 75-180 μm. This is because the laser cladding process requires preheating and heat preservation at 450-500° C., which means the heat input is relatively high, and the corresponding powder particle size can be coarser.

[0020] The present invention provides an application of the iron-based high-temperature alloy powder, wherein the powder is laser-clad on the surface of a part to form a coating.

[0021] Furthermore, the thickness is 1.0-2.0 mm.

[0022] Furthermore, during laser cladding, synchronous induction heating equipment is used for preheating and heat preservation to maintain the surface temperature of the workpiece at 450-500°C.

[0023] Furthermore, the room temperature hardness is 55-60HRC, the hardness at 1000°C is 250-300HV, and the tensile strength at 1000°C is greater than 250MPa.

[0024] Furthermore, the friction coefficient is less than 0.2 at 1000°C.

[0025] Furthermore, after stress relief annealing at 600°C for 4 hours, the number of 1000°C thermal shock cycles without cracking is greater than 20.

[0026] Furthermore, the application of iron-based high-temperature alloy powder is used for surface strengthening of the plug of seamless steel pipe piercing machine.

[0027] The iron-based high-temperature alloy powder of the present invention is applied to prepare a coating on the surface of a part by a laser cladding method: laser cladding has the advantages of low heat input, low dilution rate, small residual stress and deformation, forming a dense metallurgical bond with the substrate, and forming a finer microstructure.

[0028] The characteristics of the iron-based high-temperature alloy powder coating of the present invention are:

[0029] 1) The thickness of the iron-based high-temperature alloy coating is 1.0-2.0mm: If the thickness is less than 1.0mm, the coating may fail prematurely due to its thinness; if the thickness is greater than 2.0mm, it will increase the cost and increase the difficulty of the laser cladding process.

[0030] 2) The coating preparation uses synchronous induction heating equipment for preheating and insulation, and the temperature is maintained at 450-500°C. This is the optimal temperature obtained after a large number of tests: when the temperature is lower than 450°C, laser cladding is prone to cracks; when the temperature is higher than 500°C, the heat input is too large, resulting in large deformation, and the laser cladding layer is also prone to collapse.

[0031] 3) The room temperature hardness of the iron-based high-temperature alloy coating is 55-60HRC, the hardness at 1000℃ is 250-300HV, and the tensile strength at 1000℃ is greater than 250MPa, in order to ensure that it has good high-temperature mechanical properties; the friction coefficient of the iron-based high-temperature alloy coating at 1000℃ is less than 0.2, in order to ensure that it has good wear resistance; after stress relief annealing at 600℃ / 4h, the iron-based high-temperature alloy coating can withstand more than 20 thermal shock cycles at 1000℃ without cracking, in order to ensure that it has good resistance to cold and hot fatigue.

[0032] 4) The application of iron-based high-temperature alloy powder is used to strengthen the surface of seamless steel pipe piercing plugs. When rolling high-alloy steel, the strengthened piercing plug can pierce more than 15 pipes, up from the current 4-5.

[0033] In summary, the iron-based high-temperature alloy powder of the present invention can solve the disadvantage of the existing iron-based high-temperature alloy material that the operating temperature is lower than 800°C, and realize the application of the iron-based high-temperature alloy material at 1000°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a morphology diagram of the iron-based high-temperature alloy powder according to Example 1 of the present invention;

[0035] Figure 2 This is a metallographic photograph of the laser cladding layer of Example 1 of the present invention;

[0036] Figure 3 This is a microstructure photograph of the laser cladding layer of Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to better understand the present invention, the materials and methods of the present invention are further described in detail below with reference to the examples.

[0038] Example 1

[0039] The present invention discloses an iron-based high-temperature alloy powder having the following chemical composition and mass percentages: 0.5% C, 18.0% Cr, 16.0% Ni, 12.0% Mo, 12.0% Nb, 0.5% Si, 2.0% S, and 39.0% Fe. The powder particle size is 75 to 180 μm.

[0040] The iron-based high-temperature alloy powder of this embodiment was applied to the plug surface of a φ133 mm piercing machine by laser cladding to prepare a coating with a thickness of 1.0 mm.

[0041] During laser cladding, synchronous induction heating equipment is used for preheating and insulation to maintain the workpiece surface temperature at 500°C.

[0042] Figure 1 This is the morphology diagram of the iron-based high-temperature alloy powder of this embodiment. It can be seen that the powder morphology is good, the sphericity is high, and the proportion of hollow powder and satellite powder is small.

[0043] Figure 2 This is a metallographic photograph of the coating obtained by laser cladding in this embodiment. It can be seen that the cladding layer has no defects such as cracks and pores, and forms a good metallurgical bond with the substrate.

[0044] Figure 3 This is a microstructure picture of the laser cladding layer of this embodiment. It can be seen that there are some precipitated phases on the dendrite matrix. It is these precipitated phases that improve the high-temperature strength and wear resistance of the coating.

[0045] Example 2

[0046] The present invention discloses an iron-based high-temperature alloy powder having the following chemical composition and mass percentages: 0.4% C, 19.0% Cr, 15.0% Ni, 11.25% Mo, 11.25% Nb, 0.7% Si, 1.8% S, and 40.6% Fe. The powder particle size is 75 to 180 μm.

[0047] The iron-based high-temperature alloy powder of this embodiment is applied to the plug surface of a φ150mm punch by laser cladding to prepare a coating with a thickness of 1.5mm.

[0048] During laser cladding, synchronous induction heating equipment is used for preheating and insulation to maintain the surface temperature of the workpiece at 480°C.

[0049] Example 3

[0050] The present invention discloses an iron-based high-temperature alloy powder having the following chemical composition and mass percentages: 0.6% C, 20.0% Cr, 14.0% Ni, 10.5% Mo, 10.5% Nb, 1.0% Si, 1.5% S, and 41.9% Fe. The powder particle size is 75 to 180 μm.

[0051] The iron-based high-temperature alloy powder of this embodiment was applied to the plug surface of a φ435 mm piercing machine by laser cladding to prepare a coating with a thickness of 2.0 mm.

[0052] During laser cladding, synchronous induction heating equipment is used for preheating and insulation to maintain the surface temperature of the workpiece at 450°C.

[0053] The following performance tests were conducted on Examples 1-3 and the corresponding untreated punching machine plugs (Comparative Examples 1-3): (1) Room temperature hardness of the coating: The hardness of the coating at room temperature was measured using a Rockwell hardness tester, and the hardness was measured at five points, and the average value was taken; (2) High temperature hardness of the coating: The Vickers hardness of the coating at 1000°C was measured, and the average value was taken; (3) High temperature strength of the coating: The high temperature tensile properties of the coating at 1000°C were measured using a high temperature tensile testing machine; (4) Friction coefficient of the coating: The wear properties of the coating at 1000°C were measured using a high temperature friction and wear testing machine; (5) Thermal shock performance of the coating: The coating was first subjected to stress relief annealing by heating to 600°C and holding for 4 hours; then the coating sample was heated to 1000°C in a muffle furnace and held for 10 minutes, the sample was taken out and cooled to room temperature by rinsing with running tap water, which was considered as one cycle; the above steps were repeated multiple times until cracks appeared on the surface of the sample, and the number of cycles when cracks appeared was counted; (6) The plugs of Examples 1-3 and Comparative Examples 1-3 were put into use online to test their service life. The results are shown in Table 1.

[0054] Table 1

[0055]

[0056]

[0057] As can be seen from the above, the coating prepared from the iron-based high-temperature alloy powder of the present invention has good high-temperature mechanical properties, good wear resistance, and also good resistance to cold and hot fatigue. Therefore, after the punch head is laser-claded with iron-based high-temperature alloy powder to form a high-performance coating, its service life is increased by more than 3 times.

Claims

1. An iron-based high-temperature alloy powder, characterized in that: Its chemical composition and mass percentage are: 0.4-0.6% C, 18.0-20.0% Cr, 14.0-16.0% Ni, 10.5-12.0% Mo, 10.5-12.0% Nb, 0.5-1.0% Si, 1.5-2.0% S; the balance is Fe and inevitable impurities.

2. The iron-based high-temperature alloy powder according to claim 1, characterized in that: The mass percentage of Fe element is ≥39.0%, the mass percentage ratio of Mo element and Nb element is 1:1, and the mass percentage ratio of Ni element and (Mo+Nb) element is 1:1.

5.

3. The iron-based high-temperature alloy powder according to claim 1, characterized in that: The particle size range of the iron-based high-temperature alloy powder is 75 to 180 μm.

4. An application of an iron-based high-temperature alloy powder, characterized in that: The iron-based high-temperature alloy powder according to any one of claims 1 to 3 is laser clad on the surface of a part to form a coating.

5. The use of the iron-based high-temperature alloy powder according to claim 4, characterized in that: The coating thickness is 1.0-2.0mm.

6. The use of the iron-based high-temperature alloy powder according to claim 4, characterized in that: During laser cladding, synchronous induction heating equipment is used for preheating and insulation to maintain the surface temperature of the workpiece at 450-500℃.

7. The use of the iron-based high-temperature alloy powder according to claim 4, characterized in that: The room temperature hardness of the coating is 55-60HRC, the hardness at 1000℃ is 250-300HV, and the tensile strength at 1000℃ is greater than 250MPa.

8. The use of the iron-based high-temperature alloy powder according to claim 4, characterized in that: At 1000℃, the friction coefficient of the coating is less than 0.

2.

9. The use of the iron-based high-temperature alloy powder according to claim 4, characterized in that: After stress relief annealing at 600℃ for 4h, the coating can withstand thermal shock cycles without cracking for more than 20 times at 1000℃.

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