顶柱（KO）是在高温、高频热锻工况下热锻组合模的关键易损件，其直接承受锻锤的冲击载荷，约束高温坯料在型腔中的塑性流动，最后顶出套圈成形锻坯。在成形过程中，顶柱表层材料发生的大压缩应变-恢复、高温加热-水冷却的循环热疲劳、高温加热的回火软化、表面高温氧化起皮、表面上坯料塑性流动作用，会使顶柱发生早期失效。对顶柱的失效行为和形成机制进行分析，可为延长热锻模的使用寿命提供理论支持。

The kick-out (KO) of hot forging combination-die with high temperature and high frequency of impacting was the consumable key part,it directly bore the impact load by the hammer head,constrained the plastic flow of hot blank within the die cavity and kicked out the as-formed bearing blank. In the forming process, the surface material of the kick-out underwent large compressive strain-recovery, cyclic thermal fatigue of high temperature heating-water cooling, annealing softening of high temperature heating, skinning of surface high temperature oxidation, and plastic flow of billet on the surface,which made the kick-out fail at an early stage. The analysis of failure behavior and formation mechanism of kick-out could provide theoretical support for prolonging the service life of hot forging die.