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镍包覆碳化钛复合粉体的制备及真空烧结性能

Preparation and vacuum sintering properties of Ni coated TiC composite powders

  • 摘要: 采用浸渍-流化床还原工艺在碳化钛粉末表面沉积了金属镍纳米颗粒,随后利用镍催化剂自催化化学镀反应制备高均匀性的镍包覆碳化钛粉体,通过真空烧结工艺制备了TiC–Ni金属陶瓷。采用扫描电子显微镜、X射线衍射仪分析了镍包覆碳化钛粉体以及TiC–Ni金属陶瓷的微观形貌和物相组成,并与相同烧结工艺下混合粉体制备的TiC–Ni金属陶瓷进行性能比较。结果表明:金属镍颗粒能够非常均匀地沉积在碳化钛粉末表面,相比于镍催化剂含量(质量分数),颗粒尺寸是影响化学镀镍沉积速率的决定性因素,镍颗粒越小,沉积速率越高。当镍催化剂质量分数为0.2%时,镍颗粒平均尺寸约为22 nm,化学镀镍沉积速率达到最高值3.56 mg·g−1·min−1,以此制备了高均匀性的TiC–20Ni包覆粉体(镍质量分数20%),当烧结温度为1410 ℃时,TiC–20Ni包覆粉体烧结样品相对密度高达99.54%。相比于混合粉体,包覆粉体中镍的均匀分布不仅避免了烧结组织中“镍池”的产生,还能够有效抑制因碳化钛直接接触导致的高温合并长大,包覆粉体真空烧结样品表现出更优异的力学性能,硬度为HV1.0 (2214±68),横向断裂强度为(1152±20) MPa。

     

    Abstract: The nickel (Ni) nanoparticles were deposited on the surface of titanium carbide (TiC) powders by the impregnation-fluidized bed reduction process. The highly uniform Ni coated TiC powders were prepared through the nickel-catalyzed autocatalytic electroless plating reaction. The TiC–Ni cermets were subsequently fabricated by vacuum sintering. The microstructure and phase component of the Ni coated TiC powders and TiC–Ni cermets were characterized by scanning electron microscopy and X-ray diffraction. The performances of the TiC–Ni cermets using the Ni coated TiC powders and the mixed powders under the same sintering conditions were conducted. The results show that the Ni particles are uniformly deposited on the TiC powder surface. Compared with Ni catalyst content (mass fraction), Ni particle size dominates the electroless rate of Ni in electroless plating, with smaller Ni particles yielding higher deposition rates. When the Ni catalyst content is 0.2%, the average Ni particle size is approximately 22 nm, achieving a maximum electroless plating rate of 3.56 mg·g−1·min−1. Based on this, the highly uniform TiC–20Ni coated powders (Ni mass fraction is 20%) are prepared, and the TiC–20Ni coated sintered samples achieve the relative density of 99.54% at 1410 ℃. Compared to the cermets fabricated by mixed powders, the homogeneous Ni distribution in the coated powders not only prevents the formation of “Ni pools” in the sintered structure, but also effectively suppresses the high-temperature coalescence and grain growth caused by the direct TiC contact. As a result, the sintered samples fabricated by the coated powders exhibit the superior mechanical properties, including Vickers hardness of HV1.0 (2214±68) and transverse rupture strength of (1152±20) MPa.

     

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