Abstract: Abstract The small head of the 93WNiFe tungsten alloy rivet top iron broke during operation. The reasons for the fracture of the top iron were analyzed using macroscopic observation, chemical composition analysis, scanning electron microscopy and energy spectrum analysis, metallographic examination, density testing, hardness testing. The results show that the fracture property of tungsten alloy top iron was brittle fracture, and the crack originated from the root of the R angle at the working small head of the top iron, where the cross-section changed and promoted crack initiation. During the heat treatment of tungsten alloy, incomplete liquid-phase sintering resulted in small tungsten particles and the lack of a firmly bonded network like bonding phase between particles, led to a decrease in the bonding strength of the internal interface of the alloy material. When the alloy was subjected to stress, microcracks propagated from the grain interface with weaker bonding strength, ultimately led to the fracture of the top iron.