A method for preparing a ni-cr alloy target

Abstract

This invention discloses a method for preparing NiCr alloy sputtering targets, belonging to the field of powder metallurgy technology. The preparation method is as follows: S1, by weight percentage, Ni powder is 38-42 wt% and Cr powder is 58-62 wt%; S2, zirconium balls are added to the raw material at a weight ratio of 1:6 in a mixing tank, argon gas is introduced, and the mixture is then mixed in a ball mill; S3, after the NiCr alloy powder is loaded into a mold, it is pre-pressed in a furnace to 5-8 MPa, held for 5-10 minutes, and then depressurized; a vacuum is drawn to below 10 Pa, and the temperature is raised to 1150-1200℃ in three stages, then held at that temperature and pressurized at a uniform rate to 30-40 MPa. After sintering, a NiCr alloy target blank is obtained, which is then machined to obtain a NiCr alloy target of suitable size. The NiCr alloy target prepared by this invention has low oxygen content, high relative density, and uniform grain size, effectively ensuring the quality of the sputtered film.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a method for preparing NiCr alloy targets. Background Technology

[0002] In the coating industry, nickel-chromium (NiCr) alloy sputtering targets, prepared by adding Cr to high-purity Ni, possess excellent properties such as heat resistance, wear resistance, and corrosion resistance. These properties have led to their widespread application in high-tech industries such as surface-strengthening thin films, low-emissivity (Low-E) glass, microelectronics, magnetic recording, semiconductors, and thin-film resistors. Consequently, the demand for NiCr alloy sputtering targets is increasing, along with higher requirements for their performance, such as density, purity, grain size and distribution, uniformity, and grain orientation. However, existing NiCr alloy sputtering targets still suffer from quality issues, such as low raw material utilization, high oxygen content, uneven grain size, and difficulty in controlling grain orientation. These problems negatively impact the quality of the sputtered film. Patent document CN115522086A provides a method for preparing NiCr alloy sputtering targets. This method uses a traditional preparation process of melting, casting, and hot rolling to prepare a NiCr alloy sputtering target. However, NiCr alloy is prone to segregation during melting, resulting in uneven composition and cracking during hot rolling. At the same time, the high internal pressure during hot isostatic pressing hinders the removal of gas between powders, resulting in a high oxygen content in the NiCr alloy. Patent document CN113088909A provides a hot pressing method for preparing nickel-chromium alloy sputtering targets. The method includes the following steps: (1) preparing nickel-chromium alloy powder with a Cr content of 30-80 wt%, loading it into a mold and sealing it; (2) hot pressing and sintering the sealed mold; (3) machining the obtained nickel-chromium alloy sintered body to obtain a nickel-chromium alloy sputtering target. This method employs hot-pressing sintering to prepare high-chromium (30-80 wt%) nickel-chromium alloys with characteristics such as density ≥99%, fine grain size, uniform internal structure, and magnetic flux ≥99%. However, this method does not control the oxygen content in the target material and is unsuitable for preparing NiCr alloy targets with Ni content of 38-42 wt% and Cr content of 58-62 wt% and low oxygen content. Therefore, there is an urgent need to develop a method for preparing NiCr alloy targets, using which the prepared nickel-chromium alloy targets have low oxygen content. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing NiCr alloy targets, so as to solve the problems of high oxygen content and uneven grain size in NiCr alloy targets.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing a NiCr alloy target includes the following steps:

[0006] S1. Raw material preparation: By weight percentage, the amount of Ni powder is 38-42wt%, the amount of Cr powder is 58-62wt%, the purity of Ni powder is 2N8 and the particle size is 5-10μm, and the purity of Cr powder is 3N5 and the particle size is 325 mesh.

[0007] S2. Ball Milling and Powder Mixing: Weigh zirconium balls according to a zirconium ball to raw material weight ratio of 1:6. Place the zirconium balls and raw material into a mixing container, and purge the container with argon gas. After purging, mix the powder using a drum ball mill. During mixing, remove the mixing container every 30 minutes and shake it up and down to ensure uniform mixing. After mixing, the NiCr alloy powder can be directly hot-pressed and sintered, or it can be vacuum-stored for later use. NiCr alloy powder that has been vacuum-stored for a period of time before use needs to be mixed again for 2 hours using the above method to avoid segregation caused by prolonged powder storage.

[0008] S3. Hot Press Sintering: Cut graphite paper to the appropriate size and place it into a graphite mold. Load NiCr alloy powder into the graphite mold and sinter two products at a time. Separate the powder between the two products with graphite paper and a graphite gasket to prevent the target material from sticking to the graphite mold. After loading the mold, pre-pressurize in a furnace to 5-8 MPa, hold for 5-10 minutes, and then release the pressure. Evacuate to below 10 Pa, raise the temperature to 580-650℃ in the first stage, 1020-1060℃ in the second stage, and 1150-1200℃ in the third stage. Hold at this temperature and apply pressure at a uniform rate to 30-40 MPa. Sinter for 90-140 minutes to obtain the NiCr alloy target blank. Remove the graphite paper from the surface of the target blank and perform grinding, rough grinding, EDM, turning, and milling to obtain a target material of suitable size. Perform relevant defect and density tests. If no abnormalities are found, vacuum pack.

[0009] Furthermore, in S2, the ratio of large spheres to small spheres in the zirconium spheres is 1:7.

[0010] Furthermore, in S2, the diameters of the large and small zircon spheres are Φ20 and Φ15, respectively.

[0011] Furthermore, the inflation time in S2 is 15 minutes.

[0012] Furthermore, in S2, the ball mill speed is 230 r / min, and the mixing time is 12 h.

[0013] Furthermore, in S3, the first stage heating rate is 15℃ / min, the second stage heating rate is 7.5℃ / min, and the third stage heating rate is 4℃ / min.

[0014] Furthermore, the uniform pressurization rate in S3 is 0.6 MPa / min.

[0015] Furthermore, in the machining process described in S3, the feed rate used in the grinding process is 10 μm.

[0016] The beneficial effects of this invention are:

[0017] 1. The preparation process of this invention belongs to powder metallurgy. Powder is used as raw material for hot pressing. During the sintering process, the temperature is controlled in three stages to ensure that the hot pressing temperature does not exceed the melting point. Since the grain boundary hinders the diffusion of components, the powder is not prone to segregation during the hot pressing process. At the same time, the negative pressure inside the vacuum hot pressing sintering is also conducive to the removal of gas, further ensuring the low oxygen content of the NiCr alloy target.

[0018] 2. This invention provides a method for preparing NiCr alloy targets, which improves the accuracy of NiCr alloy target composition, and the target has high relative density and uniform grain size, effectively ensuring the quality of sputtered films. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1

[0021] A method for preparing a NiCr alloy target includes the following steps:

[0022] S1. Raw material composition: Ni powder 40wt%, Cr powder 60wt%.

[0023] S2. Ball Milling and Powder Mixing: Weigh zirconium balls according to a zirconium ball to raw material weight ratio of 1:6, with a ratio of large zirconium balls (Φ20) to small zirconium balls (Φ15) of 1:7. Add the weighed raw material and zirconium balls to a polyurethane mixing tank, and continuously fill the mixing tank with argon gas for 15 minutes. After filling, seal the mixing tank and place it on a drum ball mill. Set the speed to 230 r / min and mix for 12 hours. During this period, manually remove the tank every 30 minutes and shake it up and down for 2 minutes to ensure that the NiCr alloy powder is mixed evenly.

[0024] S3. Hot Pressing Sintering: Graphite paper of suitable size is used to isolate the powder from the graphite mold. NiCr alloy powder is loaded into the graphite mold and pre-pressed at a pressure of 5.4 MPa for 10 minutes, after which the pressure is released. A vacuum of 9 Pa is applied, and the temperature is uniformly increased to 600℃ at a rate of 15℃ / min, then to 1050℃ at a rate of 7.5℃ / min, and finally to 1170℃ at a rate of 4℃ / min. Pressure is then applied and maintained at this temperature until a pressure of 36 MPa is reached at a rate of 0.6 MPa / min. The mixture is then sintered at 1170℃ and 36 MPa for 12 hours to obtain the NiCr alloy target blank. The NiCr alloy target material is then obtained by grinding. The target density was tested using the Archimedes displacement method, and the relative density of the target was greater than 99%. The carbon content of the target was measured to be 352 ppm using a carbon-sulfur detector, and the oxygen content was measured to be 677 ppm using an oxygen-nitrogen-hydrogen detector. The Ni content was measured to be 40.28% using a titration method. The purity of the target was measured to be ≥99.95% using a GDMS instrument. The magnetic flux of the target was measured to be 99.9% using a magnetic flux meter.

[0025] Example 2

[0026] A method for preparing a NiCr alloy target includes the following steps:

[0027] S1. Raw material composition: Ni powder 42wt%, Cr powder 58wt%.

[0028] S2. Ball Milling and Powder Mixing: Weigh zirconium balls according to a zirconium ball to raw material weight ratio of 1:6, with a ratio of large zirconium balls (Φ20) to small zirconium balls (Φ15) of 1:7. Add the weighed raw material and zirconium balls to a polyurethane mixing tank, and continuously fill the mixing tank with argon gas for 15 minutes. After filling, seal the mixing tank and place it on a drum ball mill. Set the speed to 230 r / min and mix for 12 hours. During this period, manually remove the tank and shake it up and down for 2 minutes every 30 minutes. After mixing, vacuum store the NiCr alloy powder.

[0029] S3. Hot Pressing and Sintering: Graphite paper of suitable size is used to isolate the powder and the graphite mold. The NiCr alloy powder described in S2 is mixed again for 2 hours according to the mixing method in S2. The mixture is then placed into the graphite mold for pre-pressing at a pressure of 6.5 MPa. After holding the pressure for 10 minutes, the pressure is released. A vacuum of 7 Pa is applied, and the temperature is uniformly increased to 640℃ at a heating rate of 15℃ / min, then to 1020℃ at a heating rate of 7.5℃ / min, and finally to 1150℃ at a heating rate of 4℃ / min. Pressure is then applied and maintained at this temperature until it reaches 30 MPa at a pressure rate of 0.6 MPa / min. The mixture is then sintered at 1150℃ and 30 MPa for 12 hours to obtain the NiCr alloy target blank. The blank is then machined to obtain the NiCr alloy target material. The target material was tested and found to have a relative density greater than 99%, a carbon content of 358 ppm, an oxygen content of 683 ppm, a Ni content of 42.87%, a purity of ≥99.95%, and a magnetic flux of 99.9%.

[0030] Comparative Example 1

[0031] A nickel-chromium alloy sputtering target was prepared using a hot-pressing method provided by Chinese Patent CN113088909A. In this preparation process, the nickel-chromium alloy target with a Cr content of 60wt% was tested by an oxygen, nitrogen, and hydrogen detector and found that the oxygen content was 798ppm, which is much higher than the oxygen content of the target prepared with the same Cr content in Example 1. Therefore, a three-stage temperature control method was used to effectively regulate the atomic diffusion inside the material at high temperature, while reducing the temperature difference between the heating element and the target in the furnace at high temperature, reducing the heat transfer rate, and thus further regulating the oxygen content, resulting in a uniform grain distribution and high relative density of the target.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a NiCr alloy target, characterized in that, Includes the following steps: S1. Raw material preparation: By weight percentage, Ni powder is 38-42wt% and Cr powder is 58-62wt%; S2. Ball milling and powder mixing: NiCr alloy powder is obtained by ball milling zirconium balls and raw materials under an argon atmosphere. During the powder mixing process, the mixing bucket is removed and shaken up and down for 2-3 minutes every 30 minutes. S3. Hot pressing sintering: After NiCr alloy powder is loaded into the mold, it is pre-pressed in the furnace to 5-8MPa and then held for 5-10 minutes before depressurization. The vacuum is then reduced to below 10Pa. The temperature is increased to 580-650℃ in the first stage, 1020-1060℃ in the second stage, and 1150-1200℃ in the third stage. The temperature is held and the pressure is increased at a uniform rate to 30-40MPa. After sintering for 90-140 minutes, the target blank is obtained. After grinding, the NiCr alloy target material is obtained. The constant pressurization rate in S3 is 0.6 MPa / min.

2. The method for preparing a NiCr alloy target according to claim 1, characterized in that, The weight ratio of zirconium balls to raw materials in S2 is 1:

6.

3. The method for preparing a NiCr alloy target according to claim 2, characterized in that, The zirconium spheres consist of large spheres and small spheres, with a ratio of 1:7 between the large and small spheres.

4. The method for preparing a NiCr alloy target according to claim 3, characterized in that, The diameters of the large ball and the small ball are Φ20 and Φ15, respectively.

5. The method for preparing a NiCr alloy target according to claim 1, characterized in that, The ball milling speed in S2 is 230 r / min.

6. The method for preparing a NiCr alloy target according to claim 1, characterized in that, The ball milling time in S2 is 12 hours.

7. The method for preparing a NiCr alloy target according to claim 1, characterized in that, In S3, the first stage heating rate is 15℃ / min, the second stage heating rate is 7.5℃ / min, and the third stage heating rate is 4℃ / min.