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 because 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 microstructure 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.