低温退火对激光粉末床熔融成形René104Sc镍基高温合金显微组织和残余应力的影响

Effects of low temperature annealing on microstructure and residual stress of René104Sc nickel-base superalloy fabricated by laser powder bed fusion

增材制造残余应力会导致成形件发生变形甚至开裂,严重降低力学性能。本文系统观察和分析激光粉末床熔融成形René104Sc镍基高温合金在低温退火过程中显微组织的演变及其对残余应力的影响。结果表明:成形态合金经过退火处理后,胞状组织消失,织构强度降低,显微组织更加均匀,残余应力得到释放。其中,500和600℃退火后,显微组织未发生明显变化,残余应力略微降低;800℃退火后,合金样品中心的残余应力由63 MPa下降至21 MPa,析出大量γ′相,合金发生脆断,伸长率从(25.2±2.6)%下降至(4.7±1.6)%;700℃退火后,合金发生部分再结晶,样品中心的残余压应力由成形态的63 MPa下降至29MPa,综合力学性能最优,硬度(HV_(0.3))和抗拉强度分别为499±4和(1 461±7) MPa,比成形态(423±9,(935±25) MPa)分别提高18%和56%。这一研究结果为消除增材制造镍基高温合金部件的残余应力,防止在存放或后续热处理过程中开裂提供了一条有效途径。

Residual stress in additive manufacturing can cause deformation or even cracking of as-built parts,seriously reducing mechanical properties.In this paper,the microstructure evolution and its effect on residual stress of laser powder bed fusion fabricated René104Sc nickel-base superalloy during low temperature annealing were systematically observed.The results show that after annealing treatment,the cellular structure disappears,the texture strength decreases,the microstructure becomes more uniform and the residual stress is released.After annealing at 500 and 600℃,the microstructure has no obvious change and the residual stress decreases slightly.After annealing at 800℃,the residual stress in sample center decreases from 63 MPa to 21 MPa,and a large amount ofγ′phase precipitates in the alloy,resulting in brittle fracture and elongation decreases from(25.2±2.6)%to(4.7±1.6)%.After annealing at 700℃,the alloy undergoes partial recrystallization,the residual compressive in sample center decreases from 63 MPa to 29 MPa,and its comprehensive mechanical properties are the best with hardness(HV_(0.3))and tensile strength of 499±4 and(1461±7)MPa,respectively,which are 18%and 56%higher than that as-built one(423±9,(935±25)MPa).The results provide an effective way to eliminate the residual stress in the additive manufacturing nickel-base superalloy parts and prevent cracking in the storage or post heat treatment process.