The objective of this work was to explain a relationship between a distribution of carbide particles in overlay composite alloys and the size of abrasive sand on abrasive wear. The overlay composite alloys were fabricated by plasma transfer arc powder welding. Reinforcing powders of Cr-carbide and Ti-carbide were mixed with Co-base alloy powder (stellite powder), respectively, and the mixing ratio of those powders were 80: 20, 60: 40 and 40: 60. The volume fraction of non-fused carbide particles and crystallized carbides increased with the increases of the mixing ratio. The average hardness of matrix including Cr-carbide powder increased with increase of the mixing ratio, while that of matrix including Ti-carbide did not depend on the mixing ratio.
In order to assess the resistance to abrasive wear of the overlay composite alloys, a rubber wheel abrasion test was carried out on the surface using three size of abrasive sands, respectively. Weight loss caused by wearing decreased as the amound of carbide particles increases. Especially, the abrasive wear resistance of the composite alloys including Cr-carbide powder depended on the volume fraction of non-fused Cr-carbide particles including needle like carbide.
On the distribution of carbide particles, distances between carbide particles have been measured to estimate a value of matrix mean free path (λm) from which the abrasive wear resistance can be appreciated. It is found that weight loss caused by wearing decreased when a value of λm/Ds (the size of abrasive sand) became less than 1. Within the value of λm/Ds below 1, the abrasive wear resistance of composite alloy including Cr-carbide was better than the composite alloy including Ti-carbide. The Ti-carbide particles were crushed by larger abrasive sands, and hence its resistance to abrasive wear decreased.
