以BNi2非晶为中间层的CB2耐热钢瞬时液相扩散连接的接头组织和性能研究

Microstructure and mechanical properties of transient liquid phase bonded joints of CB2 ferritic heat resistant steels with amorphous BNi-2 interlayer

摘要:

本文主要研究采用BNi2非晶态中间层的CB2耐热钢瞬时液相扩散连接接头组织和性能,及焊后热处理对接头组织和性能的影响。富Cr硼化物(CrB, CrB2, Cr2B3, Cr3B4 and Cr5B3)和Cr-Mo硼化物出现在接头的过渡区和扩散影响区,其尺寸和数量在等温凝固完成时达到最大值。随着连接温度和时间的增加,富Cr的硼化物和Cr-Mo硼化物逐渐减少,而BN相逐渐增加。经过焊后热处理后,接头的富Cr硼化物几乎全部消失,而BN相的尺寸和数量增加。在热处理之前,焊接温度为1150°C ,保温时间1800s的接头有最大的拉伸强度为934 MPa,延伸率为5.3%。通过焊后热处理,断裂发生在母材,延伸率提升到20%,而拉伸强度降低到720 MPa。

Abstract:

Microstructure and mechanical properties of transient liquid phase (TLP) bonded joints and the post bonding heat treatment (PBHT) for CB2 heat resistant steel using BNi-2 insert alloy were investigated. The Cr-rich borides (CrB, CrB2, Cr2B3, Cr3B4 and Cr5B3) and Cr-Mo borides generate in the transition region (TZ) and diffusion-affected zone (DAZ) reach the peak values in size and quantity when the isothermal is completed. Subsequent elevation in bonding temperature and increment in bonding time result in gradual disappearance of such Cr-rich and Cr-Mo borides, increased percent of BN precipitates. After PBHT the Cr-rich borides almost disappear while the size and amount of BN precipitates rise. The maximum tensile strength reach to 934 MPa for the joint bonded at 1150 °C for 1800 s with elongation of 5.3%. PBHT result in significant improvement in ductility of the joint as elongation of 20% is achieved with a decreased strength of 720 MPa, the fracture takes place at base materials.