WO2021083166A1 - 一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法 - Google Patents

一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法 Download PDF

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WO2021083166A1
WO2021083166A1 PCT/CN2020/124223 CN2020124223W WO2021083166A1 WO 2021083166 A1 WO2021083166 A1 WO 2021083166A1 CN 2020124223 W CN2020124223 W CN 2020124223W WO 2021083166 A1 WO2021083166 A1 WO 2021083166A1
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iron boron
neodymium iron
coercivity
corrosion resistance
improving
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French (fr)
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刘仲武
何家毅
邱万奇
余红雅
钟喜春
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South China University of Technology SCUT
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/06—Alloys based on chromium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
    • C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/58—After-treatment
    • C23C14/5806—Thermal treatment

Definitions

  • the invention belongs to the technical field of preparation of neodymium iron boron permanent magnets, and particularly relates to a method for improving the coercivity and wear resistance and corrosion resistance of neodymium iron boron magnets.
  • NdFeB rare earth permanent magnet materials Due to its excellent magnetic properties, NdFeB rare earth permanent magnet materials have been widely used in the fields of computers, aerospace, new energy, and intelligent communications. Neodymium iron boron magnets are cost-effective, small in size and have a large magnetic energy product.
  • the molding process of commercial sintered NdFeB includes composition design, smelting, crushing and powder milling, oriented compression molding, sintering, tempering, machining and surface treatment.
  • NdFeB magnets In the service process of NdFeB permanent magnet motors, in order to adapt to harsh working conditions such as high temperature and high humidity, NdFeB magnets are required to have high coercivity and good corrosion resistance.
  • Nd 2 Fe 14 B main phase
  • neodymium iron boron magnets In industrial production, the heat treatment of neodymium iron boron magnets is mostly carried out under the protection of vacuum or inert gas, which requires high heat treatment equipment, which increases production costs. Although the traditional rare earth grain boundary diffusion process can effectively improve the coercivity of the magnet, the rare earth used for diffusion is expensive, leading to higher production costs. Moreover, the addition of rare earth elements such as terbium (Tb), dysprosium (Dy), and praseodymium (Pr) will severely reduce the remanence of neodymium iron boron magnets, resulting in a decrease in the magnetic energy product.
  • Tb terbium
  • Dy dysprosium
  • Pr praseodymium
  • NdFeB magnets have a multi-phase structure and have many cavities on the surface, they are prone to interact with external media and cause corrosion, resulting in a serious decline in magnetic properties.
  • a common and effective method is to deposit corrosion-resistant metal coatings on the surface of the magnets by chemical or physical methods to improve the corrosion resistance of the magnets.
  • the traditional nickel/copper/nickel (Ni-Cu-Ni) and zinc (Zn) plating processes are mature, but they pollute the environment and are not in line with the concept of sustainable green development.
  • the physical vapor deposition method has a major advantage of being environmentally friendly, and it can ensure uniform film formation and good shape stability.
  • the Al coating prepared by the PVD method has low hardness (only 1 to 2 GPa) and is easy to be scratched and invalidated, so that the neodymium iron boron matrix is exposed to the external environment again, which is easy to be corroded.
  • coating treatment after grain boundary diffusion or tempering heat treatment has disadvantages such as low bonding force between the film layer and the magnet.
  • patents that provide methods such as passivation solution passivation or anodic oxidation to increase the hardness of the Al coating, the process is complicated and waste liquid is generated, which greatly reduces the advantages of the PVD method.
  • the Cr coating has good corrosion resistance, high hardness, and a more beautiful metallic luster.
  • the Cr coating deposited on the surface of the sintered NdFeB magnet by the PVD method has poor bonding force with the substrate, is brittle, and is easy to collapse during use.
  • non-rare earth metal elements such as aluminum (Al), chromium (Cr), copper (Cu), zinc (Zn), magnesium (Mg) and other alloys can be added to the neodymium iron boron magnet to optimize the magnet structure Structure to improve coercivity without sacrificing remanence. Compared with the traditional rare earth grain boundary diffusion, it saves the amount of rare earth elements and can improve the corrosion resistance of the magnet.
  • Al atoms can enter the main phase of neodymium iron boron, replacing the positions of boron (B) atoms to form a Nd-(Fe, Al) phase with higher anisotropy field; Al can also play a role in promoting the formation of thin layered neodymium rich The role of the phase increases the demagnetization coupling between the crystal grains of the main phase, thereby increasing the coercivity of the magnet.
  • the Cr atoms can partially replace the iron (Fe) atoms in the main phase and can also increase the coercivity of the magnet.
  • Al and Cr are two metals with surface passivation and have good corrosion resistance.
  • the purpose of the present invention is to provide a method for improving the coercivity and wear resistance and corrosion resistance of neodymium iron boron magnets.
  • a method for improving the coercivity and wear and corrosion resistance of neodymium iron boron magnets includes the following steps:
  • the Al-Cr alloy layer is prepared on the surface of the neodymium iron boron magnet matrix by magnetron sputtering, and then diffusion heat treatment is performed in the atmosphere (without inert gas or vacuum protection).
  • the Al content in the Al-Cr alloy target material is 40 to 85 wt.%, and the Cr content is 15 to 60 wt.%.
  • the source of the neodymium iron boron magnets used in the present invention is not particularly limited, and may include sintered neodymium iron boron magnets or hot-pressed and thermally deformed neodymium iron boron magnets.
  • the neodymium iron boron magnet is N38 sintered neodymium iron boron magnet.
  • the magnetron sputtering is performed in an Ar atmosphere with a pressure of 0.5 to 1.0 Pa.
  • the temperature of the magnetron sputtering substrate is 20-100°C.
  • the power density of the magnetron sputtering is 5.5 to 6.5 W/cm 2 .
  • the substrate bias voltage of the magnetron sputtering is 0-300V.
  • the sputtering time of the magnetron sputtering is 30-150 min.
  • the thickness of the Al-Cr alloy layer is 6 ⁇ m.
  • the substrate is sputter cleaned for 10 to 20 minutes under an Ar gas pressure of 1 Pa and a negative bias of -800 to -1000V before magnetron sputtering.
  • the temperature of the diffusion heat treatment is 350 to 650°C, and the holding time is 1 to 5 hours.
  • the heating rate of the diffusion heat treatment is 15-25°C/min.
  • the method of the present invention Compared with the existing surface coating treatment, grain boundary diffusion and diffusion heat treatment process for NdFeB magnets, the method of the present invention has the following advantages and beneficial effects:
  • Diffusion heat treatment after coating can allow some Al and Cr atoms to diffuse into the magnet, further adjust and optimize the structure of the magnet, improve the magnetic properties (especially the coercivity), and form a metallurgical bond at the same time, increasing the bonding force of the coating .
  • the surface of the Al-Cr alloy coating can be thermally oxidized to Al-Cr oxide by performing diffusion heat treatment in the air after coating.
  • the film structure with continuous changes in composition can effectively improve the hardness, wear resistance and corrosion resistance of the coating, while also ensuring that the coating has good toughness.
  • the color of Al coating prepared by PVD is white and lacks metallic luster, but after adding Cr element, the coating presents silver-white metallic luster, the decoration effect is better, and it can better meet the market demand.
  • the preparation method of the coating is environmentally friendly and conforms to the environmental protection concept of green development.
  • Figure 1 is a microscopic morphology diagram and elemental analysis diagram of an Al-Cr alloy/oxide coating prepared by coating-diffusion heat treatment in Example 1;
  • FIG. 2 is a comparison diagram of the appearance and morphology of the surface of the magnet after coating-diffusion heat treatment obtained in Examples 1 to 3 and the Al film deposited on the surface of the sintered NdFeB by PVD method;
  • Figure 3 is a comparison diagram of the structure of the magnet (b) and the original magnet (a) after coating-diffusion heat treatment in Example 1;
  • Figure 4 is a comparison diagram of the magnetic properties of the magnet after coating-diffusion heat treatment in Example 1 and the original N38 neodymium iron boron magnet;
  • Fig. 5 is a comparison diagram of the corrosion resistance of the magnet after coating-diffusion heat treatment in Example 1 and the original neodymium iron boron magnet and the magnet coated with Al film by PVD method.
  • an Al-Cr target material of 85wt.% Al is used to improve the coercivity and wear and corrosion resistance of the neodymium iron boron magnet through magnetron sputtering and diffusion heat treatment:
  • the sputtering coating power supply is turned off, the background vacuum is pumped, and the sample is taken out after the furnace is cooled to room temperature.
  • the sample is placed in a heat treatment furnace with air, and the temperature is raised to 550°C at a heating rate of 15°C/min for diffusion heat treatment, and the temperature is kept for 2h. The furnace was then cooled to room temperature, and the sample was taken out.
  • the micro-morphology and element analysis diagrams of the Al-Cr alloy/oxide coating are prepared as shown in FIG. 1.
  • the comparison of the appearance of the obtained magnet surface and the PVD method deposited Al film on the surface of sintered NdFeB is shown in Figure 2. Its appearance is silver-white and has a good decorative effect.
  • the surface is compact and flat, with a hardness of 10.5 GPa; It has high bonding force with the substrate, does not break or fall off under impact impact, and can meet most of the requirements of scratch-resistant and corrosion-resistant coatings.
  • the comparison of the structure of the obtained magnet (b) and the original magnet (a) is shown in Fig. 3, and the structure of the magnet has been optimized.
  • Figure 4 shows the comparison of the magnetic properties of the obtained coating-diffusion heat treatment magnet and the original N38 neodymium iron boron magnet.
  • the magnetic performance of the magnet has been improved to a certain extent, and the coercive force is increased by about 7.2% under the condition that the remanence and the maximum magnetic energy product do not change significantly.
  • the corrosion resistance comparison diagram of the obtained coating-diffusion heat treatment magnet and the original neodymium iron boron magnet and the PVD method coated with Al film is shown in FIG. 5.
  • the corrosion resistance of the magnet is better than that of the pure Al coating prepared by the PVD method.
  • a 70wt.% Al Al-Cr target is used to improve the coercivity and wear and corrosion resistance of the neodymium iron boron magnet through magnetron sputtering and diffusion heat treatment:
  • the sputtering coating power supply is turned off, the background vacuum is pumped, and the sample is taken out after the furnace is cooled to room temperature.
  • the sample is placed in a heat treatment furnace with air, and the temperature is raised to 350°C at a heating rate of 20°C/min for diffusion heat treatment, and the temperature is kept for 5 hours. The furnace was then cooled to room temperature, and the sample was taken out.
  • the prepared Al-Cr alloy/oxide coating after coating-diffusion heat treatment, has a silver-gray film (see Figure 2), which has a good decorative effect, a compact and flat surface, and a hardness of 11.1 GPa;
  • the toughness is good, the bonding force with the matrix is high, and the coating will not crack or fall off under the impact of general impact load.
  • the coercive force is increased by about 8.7%.
  • the corrosion resistance of the magnet is better than that of PVD plating pure Al.
  • a 55wt.% Al Al-Cr target is used to improve the coercivity and wear and corrosion resistance of the neodymium iron boron magnet through magnetron sputtering and diffusion heat treatment:
  • the sputtering coating power supply is turned off, the background vacuum is pumped, and the sample is taken out after the furnace is cooled to room temperature.
  • the sample is placed in a heat treatment furnace with air, and the temperature is raised to 650°C at a heating rate of 25°C/min for diffusion heat treatment, and the temperature is kept for 1 hour. The furnace was then cooled to room temperature, and the sample was taken out.
  • the prepared Al-Cr alloy/oxide coating is a silver-gray film (see Figure 2), which has a good decorative effect, a flat surface, and a hardness of 11.6 GPa; the film is more tough Good, high bonding force with the substrate, the coating will not break or fall off under the impact of general impact load. It can meet the requirements of most scratch-resistant and corrosion-resistant films. Under the condition that there is no significant change in remanence and maximum magnetic energy product, the coercive force is increased by about 6.1%. The corrosion resistance of the magnet is better than that of PVD plating pure Al.
  • a 40wt.% Al Al-Cr target is used to improve the coercivity and wear and corrosion resistance of the neodymium iron boron magnet through magnetron sputtering and diffusion heat treatment:
  • the sputtering coating power supply is turned off, the background vacuum is pumped, and the sample is taken out after the furnace is cooled to room temperature.
  • the sample is placed in a heat treatment furnace with air, and the temperature is raised to 500°C at a heating rate of 20°C/min for diffusion heat treatment, and the temperature is kept for 2h. The furnace was then cooled to room temperature, and the sample was taken out.
  • the prepared Al-Cr alloy/oxide coating is a silver-white film, which has a good decorative effect, a compact and flat surface, and a hardness of 9.7 GPa; the film has good toughness, and The bonding force of the matrix is high, and the coating will not break or fall off under the impact of general impact load. It can meet the requirements of most scratch-resistant and corrosion-resistant films. Under the condition that there is no significant change in remanence and maximum magnetic energy product, the coercive force is increased by about 4%. The corrosion resistance of the magnet is better than that of PVD plating pure Al.

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Abstract

本发明属于钕铁硼永磁体制备技术领域，公开了一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法。以Al-Cr合金作为靶材，通过磁控溅射在钕铁硼磁体基体表面制备Al-Cr合金层，然后在大气气氛下进行扩散热处理。本发明获得的Al-Cr镀层经过扩散热处理工艺可有效提高钕铁硼磁体的磁性能，特别是矫顽力。与此同时，所述的Al-Cr金属/氧化物镀层相比于纯Al镀层具有更好的金属光泽、更高的硬度和耐磨性、更好的抗划伤能力，并且具有很好的耐腐蚀性能。在空气中进行扩散热处理降低了对热处理设备的要求，生产成本低。

Description

一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法
本申请要求于2019年10月28日提交中国专利局、申请号为201911029280.8、发明名称为“一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明属于钕铁硼永磁体制备技术领域，具体涉及一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法。
背景技术
钕铁硼稀土永磁材料因拥有优异的磁性能，在计算机、航天航空、新能源和智能通讯等领域已取得了广泛的应用。钕铁硼磁体性价比高，体积小的同时具有较大的磁能积。商用烧结钕铁硼的成型工艺包括成分设计、冶炼、破碎与制粉、取向压制成型、烧结、回火、机加工及表面处理等过程。
在钕铁硼永磁电机的服役过程中，为适应高温、高湿等苛刻的工况，要求钕铁硼磁体有高的矫顽力和较好的耐腐蚀性能。然而，商用烧结钕铁硼磁体在在烧结过程中，容易在主相(Nd 2Fe 14B)的附近产生大块聚集在三角晶界处的富钕相，不利于生产较高矫顽力的磁体。这个问题可以通过后续的烧结后的回火热处理工艺或晶界扩散工艺对磁体组织进行调控优化。而工业生产中钕铁硼磁体的热处理多在真空或惰性气体的保护下进行，对热处理设备要求较高，从而增加了生产成本。传统的稀土晶界扩散工艺虽能有效提高磁体矫顽力，但扩散所用稀土价格昂贵，导致生产成本升高。而且铽(Tb)、镝(Dy)、镨(Pr)等稀土元素的加入会严重降低钕铁硼磁体的剩磁，导致磁能积下降。
此外，因为商用烧结钕铁硼磁体具有多相结构并在表面存在较多空洞，容易与外界介质发生作用并产生腐蚀，导致磁性能严重下降。针对钕铁硼磁体耐腐蚀性能差这个问题，常用有效的方法是用化学或物理的方法在磁体表面沉积耐蚀金属镀层，从而提高磁体耐蚀性。传统的电镀镍/铜/镍(Ni-Cu-Ni)以及镀锌(Zn)工艺成熟，但对环境造成污染，不符合可持续 绿色发展的理念。近年来，人们采用真空蒸镀或者电弧离子镀等气相沉积的方法，在钕铁硼磁体表面沉积纯Al镀层。与传统的电镀法相比，物理气相沉积法(PVD)具有环境友好的一大优点，而且其可保证成膜均匀，形状稳定性好。但采用PVD法制备的Al镀层硬度较低(仅为1～2GPa)，易划伤失效，使得钕铁硼基体再次暴露在外界环境中，从而易遭腐蚀。另外，经晶界扩散或回火热处理后进行镀膜处理具有膜层与磁体结合力较低等弊端。虽然有专利提供了通过钝化液钝化或者阳极氧化法等方法以提高Al镀层硬度，但工艺复杂，而且会产生废液，使得PVD法的优势大打折扣。Cr镀层耐腐蚀性良好，硬度较高，有较美观的金属光泽。然而，用PVD法在烧结钕铁硼磁体表面沉积的Cr镀层，与基体结合力差，脆性大，使用过程中容易崩落。有学者提出用PVD法在烧结钕铁硼表面沉积Cr/Cr 2O 3或Al/Al 2O 3多层膜，以提高镀层硬度、增加耐磨性，但此工艺在工业生产中工艺复杂，生产成本高。
据已有报道，微量的非稀土金属元素，如铝(Al)、铬(Cr)、铜(Cu)、锌(Zn)、镁(Mg)等合金可加入至钕铁硼磁体中优化磁体组织结构，在不牺牲剩磁的条件下提高矫顽力。相比于传统的稀土晶界扩散，其更节省稀土元素的用量，而且能提高磁体的耐腐蚀性能。其中Al原子可进入钕铁硼主相中，替换硼(B)原子的位置，形成各向异性场更高的Nd-(Fe,Al)相；Al也可起到促进形成薄层状富钕相的作用，增加主相晶粒之间的去磁耦合作用，从而提高磁体矫顽力。而Cr原子则可部分替代主相中的铁(Fe)原子，亦可提高磁体矫顽力。同时Al、Cr两种金属是两种具有表面钝化作用的金属，具有良好的耐腐蚀性能。
因此，如何更好地结合磁体晶界扩散以及表面镀膜工艺，以简单、低成本的工艺制备出矫顽力较高、耐磨耐蚀性能好的钕铁硼磁体，是目前对商用钕铁硼急需解决的问题之一。
发明内容
针对以上现有技术存在的缺点和不足之处，本发明的目的在于提供一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法。
本发明目的通过以下技术方案实现：
一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，包括如下步骤：
以Al-Cr合金作为靶材，通过磁控溅射在钕铁硼磁体基体表面制备Al-Cr合金层，然后在大气气氛下(无惰性气体或真空保护)进行扩散热处理。
优选地，所述Al-Cr合金靶材中Al的含量为40～85wt.％，Cr的含量为15～60wt.％。
本发明所用的钕铁硼磁体，对其来源没有特别限制，可以包括烧结钕铁硼磁体或热压、热变形钕铁硼磁体。
优选地，所述钕铁硼磁体为N38烧结钕铁硼磁体。
优选地，所述磁控溅射在压力为0.5～1.0Pa的Ar气氛下进行。
优选地，所述磁控溅射的基体的温度为20～100℃。
优选地，所述磁控溅射的功率密度为5.5～6.5W/cm 2。
优选地，所述磁控溅射的基体偏压为0～-300V。
优选地，所述磁控溅射的溅射时间为30～150min。
优选地，所述Al-Cr合金层的厚度为6μm。
优选地，所述基体在磁控溅射之前在Ar气压力为1Pa，-800～-1000V的负偏压下溅射清洗10～20min。
优选地，所述扩散热处理的温度为350～650℃，保温时间为1～5h。
优选地，所述扩散热处理的升温速率为15～25℃/min。
与现有针对钕铁硼磁体的表面镀膜处理、晶界扩散及其扩散热处理工艺相比，本发明的方法具有如下优点及有益效果：
(1)通过镀膜后进行扩散热处理可使部分Al、Cr原子扩散至磁体内部，进一步调控优化磁体组织结构，提高磁性能(特别是矫顽力)，同时形成冶金结合，增加了镀层的结合力。
(2)扩散热处理过程中扩散物不包含稀土元素，从而在提高磁体矫顽力的同时进一步节省了稀土用量。
(3)通过镀膜后进行空气中扩散热处理能使Al-Cr合金镀层表面热氧化成Al-Cr氧化物。这种成分连续变化的膜层结构能有效提高镀层硬度、耐磨性以及耐腐蚀性能，同时也能保证镀层有较好的韧性。
(4)不使用惰性气氛或真空保护，可以降低热处理设备的要求，节省生产成本。
(5)PVD制备Al镀层颜色偏白，缺乏金属光泽，但加入Cr元素后，镀层呈现银白色的金属光泽，装饰效果更好，能更好地符合市场需求。
(6)加入Cr元素后，溅射速率加快，可在更短的时间里在磁体表面沉积出较厚的镀层。
(7)本镀层制备方法环境友好，符合绿色发展的环保理念。
附图说明
图1为实施例1中经过镀膜-扩散热处理制备的Al-Cr合金/氧化物镀层的微观形貌图及元素分析图；
图2为实施例1～3所得经过镀膜-扩散热处理的磁体表面与PVD法沉积Al膜于烧结钕铁硼表面的外观形貌对比图；
图3为实施例1经过镀膜-扩散热处理的磁体(b)与原始磁体(a)的组织结构对比图；
图4为实施例1经过镀膜-扩散热处理的磁体与原始N38钕铁硼磁体的磁性能对比图；
图5为实施例1经过镀膜-扩散热处理的磁体与原始钕铁硼磁体、PVD法镀有Al膜的磁体的耐腐蚀性对比图。
具体实施方式
下面结合实施例及附图对本发明作进一步详细的描述，但本发明的实施方式不限于此。
实施例1
本实施例采用85wt.％Al的Al-Cr靶材通过磁控溅射及扩散热处理改善钕铁硼磁体矫顽力和耐磨耐蚀性能：
(1)依据磁控溅射系统靶材尺寸，订制含85wt.％Al的Al-Cr靶材；
(2)用N38烧结钕铁硼磁体作基体，将基体抛光至镜面后，在丙酮与无水乙醇中超声清洗15分钟后，置于50℃烘箱中烘干；
(3)安装Al-Cr合金溅射靶至连接有直流溅射电源靶位，调节基体与靶材之间距离至80mm，将烘干的样品置于样品台，抽真空并开启红外烘烤至150℃，抽至本底真空度后，关闭真空烘烤，将基体冷却至室温；
(4)向真空室通入氩气(Ar)至1Pa，基体施加-900V的负偏压，开启直流溅射系统，样品在负偏压下溅射清洗15min；
(5)逐渐减少Ar气流量，使真空度维持在0.5～0.8Pa范围，将负偏压调整至-50～-80V，用5.5～6.0W/cm 2的功率密度沉积90min，可沉积出约6μm的Al-Cr合金膜(图1)；
(6)Al-Cr合金膜沉积完成后，关闭溅射镀膜电源，抽至本底真空后，炉冷却至室温后取出样品。
(7)镀膜后样品置于通入空气的热处理炉中，以15℃/min的升温速率升温至550℃进行扩散热处理，保温2h。随后炉冷至室温，取出样品。
本实施例中，经过镀膜-扩散热处理后，制备出Al-Cr合金/氧化物镀层的微观形貌图及元素分析图如图1所示。所得磁体表面与PVD法沉积Al膜于烧结钕铁硼表面的外观形貌对比图如图2所示，其外观为银白色，有较好的装饰效果，表面致密平整，硬度为10.5GPa；镀层与基体结合力高，受撞击性冲击不破裂，不脱落，能满足大部分抗划伤耐蚀镀层要求。所得磁体(b)与原始磁体(a)的组织结构对比图如图3所示，磁体组织结构得到优化。所得镀膜-扩散热处理的磁体与原始N38钕铁硼磁体的磁性能对比图如图4所示。磁体磁性能有一定的提高，在剩磁和最大磁能积没有明显变化的条件下，矫顽力提升约7.2％。此外所得镀膜-扩散热处理的磁体与原始钕铁硼磁体、PVD法镀有Al膜的磁体的耐腐蚀性对比图如图5所示。磁体耐腐蚀性能比PVD法制备的纯Al镀层更好。
实施例2
本实施例采用70wt.％Al的Al-Cr靶材通过磁控溅射及扩散热处理改善钕铁硼磁体矫顽力和耐磨耐蚀性能：
(1)依据磁控溅射系统靶材尺寸，订制含70wt.％Al的Al-Cr靶材；
(2)用N38烧结钕铁硼磁体作基体，将基体抛光至镜面后，在丙酮与无水乙醇中超声清洗15分钟后，置于50℃烘箱中烘干；
(3)安装Al-Cr合金溅射靶至连接有直流溅射电源靶位，调节基体与靶材之间距离至80mm，将烘干的样品置于样品台，抽真空并开启红外烘烤至150℃，抽至本底真空度后，关闭真空烘烤，将基体冷却至室温；
(4)向真空室通入Ar气至1Pa，基体施加-800V的负偏压，开启直流溅射系统，样品在负偏压下溅射清洗15min；
(5)逐渐减少Ar气流量，使真空度维持在0.5～0.8Pa范围，将负偏 压调整至-50～-80V，用5.5～6.0W/cm 2的功率密度沉积90min，可沉积出约6.5μm的Al-Cr合金膜；
(6)Al-Cr合金膜沉积完成后，关闭溅射镀膜电源，抽至本底真空后，炉冷却至室温后取出样品。
(7)镀膜后样品置于通入空气的热处理炉中，以20℃/min的升温速率升温至350℃进行扩散热处理，保温5h。随后炉冷至室温，取出样品。
本实施例中，经过镀膜-扩散热处理后，制备出的Al-Cr合金/氧化物镀层外观为银灰色薄膜(见图2)，有良好的装饰效果，表面致密平整，硬度为11.1GPa；薄膜的韧性较好，与基体结合力较高，受一般冲击载荷冲击镀层不破裂，不脱落。在剩磁和最大磁能积没有明显变化的条件下，矫顽力提升约8.7％。磁体耐腐蚀性能比PVD法镀纯Al的更好。
实施例3
本实施例采用55wt.％Al的Al-Cr靶材通过磁控溅射及扩散热处理改善钕铁硼磁体矫顽力和耐磨耐蚀性能：
(1)依据磁控溅射系统靶材尺寸，订制含55wt.％Al的Al-Cr靶材；
(2)用N38烧结钕铁硼磁体作基体，将基体抛光至镜面后，在丙酮与无水乙醇中超声清洗15分钟后，置于50℃烘箱中烘干；
(3)安装Al-Cr合金溅射靶至连接有直流溅射电源靶位，调节基体与靶材之间距离至80mm，将烘干的样品置于样品台，抽真空并开启红外烘烤至150℃，抽至本底真空度后，关闭真空烘烤，将基体冷却至室温；
(4)向真空室通入Ar气至1Pa，基体施加-900V的负偏压，开启直流溅射系统，样品在负偏压下溅射清洗15min；
(5)逐渐减少Ar气流量，使真空度维持在0.5～0.8Pa范围，将负偏压调整至-50～-80V，用5.5～6.0W/cm 2的功率密度沉积90min，可沉积出约6μm的Al-Cr合金膜；
(6)Al-Cr合金膜沉积完成后，关闭溅射镀膜电源，抽至本底真空后，炉冷却至室温后取出样品。
(7)镀膜后样品置于通入空气的热处理炉中，以25℃/min的升温速率升温至650℃进行扩散热处理，保温1h。随后炉冷至室温，取出样品。
本实施例中，经过镀膜-扩散热处理后，制备的Al-Cr合金/氧化物镀 层为银灰色薄膜(见图2)，有良好的装饰效果，表面平整，硬度为11.6GPa；薄膜的韧性较好，与基体结合力较高，受一般冲击载荷冲击镀层不破裂，不脱落。能满足大多数抗划伤耐蚀性薄膜要求。在剩磁和最大磁能积没有明显变化的条件下，矫顽力提升约6.1％。磁体耐腐蚀性能比PVD法镀纯Al的更好。
实施例4
本实施例采用40wt.％Al的Al-Cr靶材通过磁控溅射及扩散热处理改善钕铁硼磁体矫顽力和耐磨耐蚀性能：
(1)依据磁控溅射系统靶材尺寸，订制含40wt.％Al的Al-Cr靶材；
(2)用N38烧结钕铁硼磁体作基体，将基体抛光至镜面后，在丙酮与无水乙醇中超声清洗15分钟后，置于50℃烘箱中烘干；
(3)安装Al-Cr合金溅射靶至连接有直流溅射电源靶位，调节基体与靶材之间距离至80mm，将烘干的样品置于样品台，抽真空并开启红外烘烤至150℃，抽至本底真空度后，关闭真空烘烤，将基体冷却至室温；
(4)向真空室通入Ar气至1Pa，基体施加-900V的负偏压，开启直流溅射系统，样品在负偏压下溅射清洗15min；
(5)逐渐减少Ar气流量，使真空度维持在0.5～0.8Pa范围，将负偏压调整至-50～-80V，用5.5～6.0W/cm 2的功率密度沉积90min，可沉积出约6μm的Al-Cr合金膜；
(6)Al-Cr合金膜沉积完成后，关闭溅射镀膜电源，抽至本底真空后，炉冷却至室温后取出样品。
(7)镀膜后样品置于通入空气的热处理炉中，以20℃/min的升温速率升温至500℃进行扩散热处理，保温2h。随后炉冷至室温，取出样品。
本实施例中，经过镀膜-扩散热处理后，制备的Al-Cr合金/氧化物镀层为银白色薄膜，有较好的装饰效果，表面致密平整，硬度为9.7GPa；薄膜的韧性较好，与基体结合力较高，受一般冲击载荷冲击镀层不破裂，不脱落。能满足大多数抗划伤耐蚀性薄膜要求。在剩磁和最大磁能积没有明显变化的条件下，矫顽力提升约4％。磁体耐腐蚀性能比PVD法镀纯Al的更好。
上述实施例为本发明较佳的实施方式，但本发明的实施方式并不受上 述实施例的限制，其它的任何未背离本发明的精神实质与原理下所作的改变、修饰、替代、组合、简化，均应为等效的置换方式，都包含在本发明的保护范围之内。

Claims (12)

  1. 一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：包括如下步骤：
    以Al-Cr合金作为靶材，通过磁控溅射在钕铁硼磁体基体表面制备Al-Cr合金层，然后在大气气氛下进行扩散热处理。
  2. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述Al-Cr合金靶材中Al的含量为40～85wt.％，Cr的含量为15～60wt.％。
  3. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述钕铁硼磁体包括烧结钕铁硼磁体、热压钕铁硼磁体或热变形钕铁硼磁体。
  4. 根据权利要求1或3所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述钕铁硼磁体为N38烧结钕铁硼磁体。
  5. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述磁控溅射在压力为0.5～1.0Pa的Ar气氛下进行。
  6. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述磁控溅射的基体的温度为20～100℃。
  7. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述磁控溅射的功率密度为5.5～6.5W/cm 2。
  8. 根据权利要求1和5～7中任一项所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述磁控溅射的基体偏压为0～-300V；磁控溅射的溅射时间为30～150min。
  9. 根据权利要求8所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述Al-Cr合金层的厚度为6μm。
  10. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述磁控溅射前还包括：钕铁硼磁体基体在Ar气压力为1Pa，-800～-1000V的负偏压下溅射清洗10～20min。
  11. 根据权利要求1所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述扩散热处理的温度为350～650℃，保温时间 为1～5h。
  12. 根据权利要求11所述的一种改善钕铁硼磁体矫顽力和耐磨耐蚀性能的方法，其特征在于：所述扩散热处理的升温速率为15～25℃/min。
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