蜂窝预制体孔径对WC/Fe复合材料中W扩散均匀性的影响

为探究蜂窝预制体孔径对WC/Fe复合材料中W扩散均匀性的影响，采用真空消失模铸渗(V-EPC)工艺制备不同孔径下的复合材料。检测W质量分数分布，发现预制体孔径较小或较大时W质量分数分布不均匀；而预制体孔径适中时W质量分数分布较均匀，其原孔壁与原孔心处W质量分数与硬度相差最小，复合层耐磨性最高。基于扩散动力学进行模拟，表明W扩散均匀性同时受扩散距离与扩散时间的影响。预制体孔径较小时，扩散距离虽短，但其孔内熔体凝固较快，扩散时间较短，不利于W扩散；预制体孔径较大时，其孔内熔体凝固虽慢，扩散时间较长，但扩散距离增长，仍不利于W扩散；预制体孔径适中时，因兼顾扩散距离与扩散时间，利于W扩散。W扩散均匀性较差时，预制体原孔心处W质量分数较小，硬度也较低，一定范围内降低复合层耐磨性。 

Hole diameter of honeycomb preform governing W diffusion uniformity in WC/Fe composites

In order to investigate the effect of hole diameter in honeycomb preform on the W diffusion uniformity, the WC/Fe composites with different diameters were fabricated by vacuum expendable pattern casting (V-EPC) process. Based on the W mass fraction distribution analysis, it is found that the W distributes uniformity when the hole diameter is too large or too smallthe, while wear resistance of WC/Fe composites with the proper hole diameter of preform is the best, and the differences of the W mass fraction and hardness between initial hole wall and initial hole center are reduced. The simulation results by diffusion dynamics show that the uniformity of W diffusion is both influenced by diffusion distance and diffusion time. The W diffusion is limited when the hole diameter is samll and the diffusion distance is short although the diffusion time decreases, resluted from the fast internal matrix solidification. The W diffusion is also limited when the hole diameter is large, although the internal matrix solidifies slow and the diffusion time increases, but the diffusion distance increases. So the proper hole diameter has positive influence on the W diffusion uniformity with reasonable diffusion distance and diffusion time. On the contrary, the W diffusion uniformity is undesirable, and the W mass fraction and the hardness at the initial hole center are lower, resulting in the reduction of wear resistance within a certain range.