Effect of Heat Treatment on the Performances of Passivation Machine Drill Made of Yttrium-containing W18Cr4V Steel

Focusing on the inferior impact and thermal fatigue performances of drill made of W18Cr4 V steel which are often caused by serious segregation of carbides and the existence of large carbides particles in the steel,different annealing temperatures and quenching processes were employed to carry out the heat treatment for passivation machine drill made of yttrium-containing W18Cr4 V steel,and the microstructure,impact properties and thermal fatigue performances of the drill were respectively analyzed by SEM,impact and thermal fatigue tests.The results show that with increasing annealing temperature,both the impact properties and thermal fatigue performances of the drill are firstly improved then degraded.Step quenching is more conducive to the improvement of impact properties and thermal fatigue performances of the drill.For the passivation machine drill made of yttrium-containing W18Cr4 V steel,the optimal annealing temperature is 900℃ with optimum step quenching of 1 450℃×10 min+1 250℃×20 min.