碳化物特性对Ni3Al基表面强化复合材料组织与性能的影响

将真空常压烧结的方法制得的Cr3C2-Ni-Al和WC-Ni-Al复合焊丝氩弧堆焊于碳钢表面时,利用氩弧物理热和Ni-Al反应热,促使碳化物硬质颗粒与自生成的Ni3Al金属间化合物基体复合.XRD分析表明,在堆焊过程中两种焊丝中的Ni,Al均化合反应生成Ni3Al金属间化合物.微观组织与硬度试验表明,受各自物理特性(密度、熔点)的影响,两种碳化物硬质相在Ni3Al基体中分布均匀程度不同,其强化效果也迥异:WC仍以原始的大颗粒形态偏聚于焊层层间界面处,而起不到弥散强化作用;Cr3C2则发生分解,并反应析出条块状的Cr7C3相,均匀分布于Ni3Al基体中,很好地强化了基体材料.Cr7C3/Ni3Al复合材料的室、高温硬度远高于传统高温耐磨材料stellite合金.该合金有望成为一种新型的高温耐磨表面强化材料.

Influence of Carbides Characters on Microstructure and Properties of Ni3Al Base Surface-strengthening Composites

Two welding wires including Cr3C2-Ni-Al and WC-Ni-Al were produced by pressureless sintering in vacuum. When the welding wires were welded on the surface of carbon steel by the manual gas-tungsten arc welding, carbide particles reinforced Ni3Al base composites were formed by the physical heat of arc and Ni-Al exothermic reaction. XRD showed that Ni reacted with Al to form Ni3Al in both wires during welding. Microstructure and hardness tests showed that carbides distributed in matrix and strengthened matrix differently, which was mainly attributed to their different physical characters (such as density, melting point). WC appeared as large particles and segregated on welding interfaces, and hence the strengthening effect was small. However, Cr3C2 was decomposed during welding to form the dispersed Cr7C3 with stripe shape, which strengthened the matrix significantly. The room and high temperature hardness of Cr7C3/ Ni3Al composite was much higher than that of Stellite alloys. Cr7C3/Ni3Al composite is attractive as potential candidate for high-temperature surface wear-resistant material.