Ni含量和烧结压力对SPS法制备NiTi合金显微组织及摩擦学性能的影响

Influence of the nickel contents and sintering pressure on microstructure and tribological properties of NiTi alloy prepared by Spark Plasma Sintering

摘要:

采用高能球磨和放电等离子烧结法(SPS)在1000℃制备NiTi合金,研究镍含量和烧结压力对NiTi合金致密度、显微组织、显微硬度和摩擦学性能的影响。结果表明：通过高能球磨后,粉末颗粒尺寸减小；随着镍含量增加,Ni相衍射峰向高角度偏移。NiTi合金致密度随着烧结压力增大而增大,在5 MPa烧结压力下,合金致密度随着镍含量增加从94.7%降低到84.6%；在烧结压力高于5 MPa下,合金致密度随着镍含量增加表现出先增加后减小的趋势,在镍含量为45 wt. %时,合金致密度最低。NiTi合金主要由NiTi相、NiTi2相和Ni3Ti相组成,Ni3Ti相含量随着镍含量和烧结压力增大而增大,并且镍含量和烧结压力增大会引起Ni3Ti相晶格畸变。随着镍含量从0 wt. %增加到65 wt. %时,合金显微硬度先增大后减小,在镍含量为50 wt. %时,显微硬度最大。在相同化学成分下,合金显微硬度随着烧结压力增大而增大。增大镍含量和烧结压力会降低NiTi合金磨损率,显著提高合金耐磨性。室温下NiTi合金的磨损机制是以磨粒磨损和黏着磨损为主。

Abstract:

In this investigation, NiTi alloys were prepared by high-energy milling and spark plasma sintering (SPS) at 1000℃. The effects of the Ni content and sintering pressure on the density, microstructure, microhardness and tribological properties of NiTi alloys were also investigated. The experimental results showed that the particle sizes of the powders were decreased after high-energy ball milling, and the diffraction peaks of Ni phase were shifted to the high angle with the increase of nickel contents. As the sintering pressure increased, the relative densities of NiTi alloys were increased. At the sintering pressure of 5MPa, the relative densities of NiTi alloys were decreased from 94.7% to 84.6% with the increase of nickel contents. When the sintering pressure was higher than 5MPa, the relative densities of NiTi alloys were firstly increased and then decreased as nickel content increased. However, the lowest value of the relative density of NiTi alloys was happened at nickel content of 45 wt.%. NiTi phase, NiTi2 phase and Ni3Ti phase were presented in the microstructures of NiTi alloys. The microhardness of the alloy were firstly increased and then decreased as the nickel contents increased from 0 wt.% to 65 wt.%. The microhardness of the NiTi alloy has the biggest value at nickel content of 45 wt.%. The wear rates of NiTi alloys were reduced as the nickel content and sintering pressure increased and the wear resistance of the alloys were significantly improved. The wear mechanisms of NiTi alloys at room temperature were mainly abrasive wear and adhesive wear.