Effects of Microstructural Change in Joint Interface on Mechanical Properties of Si3N4/S.S316 joint with Ni Buffer layer

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J. Korean Ceram. Soc. > Volume 37(4); 2000 > Article

Journal of the Korean Ceramic Society 2000;37(4): 381.

Ni buffer layer를 사용한 Si3N4/S.S316 접합체에서 접합계면의 미세구조 변화가 접합체의 기계적 특성에 미치는 영향

장희석, 박상환¹, 권혁보², 최성철

한양대학교 무기재료공학과
¹한국과학기술연구원 복합기능세라믹스연구센터
²경남대학교 신소재공학과

Effects of Microstructural Change in Joint Interface on Mechanical Properties of Si3N4/S.S316 joint with Ni Buffer layer

ABSTRACT

Si3N4/stainless steel 316 joints with Ni buffer layer were fabricated by direct active brazing method (DIB) using Ag-Cu-Ti brazing alloy only and double brazing method (DOB) using Ag-Cu brazing alloy with Si3N4 pretreated with Ag-Cu-Ti brazing alloy. For the joint brazed by DIB method, Ti was segregated at the Si3N4/brazing alloy interface, but was not enough to form a stable joint interface. In addition, large amounts of Ni-Ti inter-metallic compounds were formed in tehbrazing alloy near the joint interface, which could deplete the contents of Ti involved in the interfacial reaction. However, for the joint brazed by DOB method, segregation of Ti at the joint interface were enough to enhance the formation of stable interfacial reaction products such as TiN and Ti-Si-Ni-N-(Cu) multicompounds, which restricted the formation of Ni-Tio inter-metallic compounds in the brazing alloy during brazing with Ni buffer layer. Fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was much improved by using DOB method rather than DIB method. It could be deduced that the differences of fracture strength of the joint with Ni buffer layer depending on brazing process adapted were directly affected by the formation of stable joint interface and the change in microstructure of the brazing alloy near the joint interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of Ni buffer layer in the joint was increased from 0.1 mm to 10 mm. It seems to due to the increased residual stress in the joint as the thickness of Ni buffer layer is increased. The maximum fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was 386 MPa, and the fracture of joint was originated at Si3N4/brazing alloy joint interface and propagated into Si3N4 matrix.

Key words: Silicon nitride, Active brazing, Ni buffer layer, Interfacial reaction product