农机铸件表面硼化物梯度耐磨材料的显微组织

铸造表面合金化工艺制备的合金层存在着硬度高，机械加工困难及合金层与基体结合强度较低而易剥落的缺陷，该研究针对这些缺陷进行研究，采用梯度成分设计原则，制备出不同组分及含量的梯度合金粉剂层膏块，在HT200铸铁件表面制备出硼化物梯度耐磨材料，对该材料的形成过程、微观组织及显微硬度进行了研究，发现该合金层由过渡区→中间耐磨层→表面铸铁烧结层3部分组成，中间层的微观组织为硼化物，其基体上散布着高碳铬铁颗粒，且颗粒粒径影响其与梯度材料的熔合性，并在实际农机铸铁件犁锺上进行了现场应用，结果表明，与未处理零件相比，犁锺使用寿命提高2.5倍以上。

Microstructure of the wear-resisting functional gradient borides materials on the agricultural machinery casting surface

The wear-resisting alloying layer on casting surface can be prepared by the surface alloying technique. However, the layer has obvious defects such as high hardness leading to difficultly machining, easily spalling became of low bonding strength between layer and matrix. Aimed at solving the problems, the blocks coated by different component of gradient powder layers using the principle of gradient composite design were prepared. Then wear-resisting functional gradient borides materials (FGMs) on HT200 cast iron's surface were formed, and their forming mechanism, microstructure and microhardness were studied. The results showed that the alloying layers were made up of transition region, middle wear-resisting layer and ingot particles sintering layer. Further study on the mierostructure of middle wear-resisting layer indicated that high-hardness ferrochrome particles homogeneously scattered on the boride matrix, which its size affected the fusion of the materials. Application in slade showed that the service life of treated slade was increased more than 2.5 times comparing with that of untreated slade.