Microstructure and mechanical strength of diffusion-bonded Ti 3 SiC 2 /Ni joints
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M.S. Lia) and Y.C. Zhou Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China (Received 10 April 2006; accepted 15 June 2006)
Diffusion bonding of Ti3SiC2 and nickel has been conducted at temperatures of 800 °C–1100 °C for 10–90 min under 6–20 MPa in a vacuum. The phase composition and microstructure of the joints were investigated by x-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The total diffusion path of the joining is determined to be Ni/Ni31Si12 + Ni16Ti6Si7 + TiCx/Ti3SiC2 + Ti2Ni + TiCx/ Ti3SiC2. The growth of the reaction layer follows parabolic law, and the temperature dependence of the reaction constant, k, can be expressed as k ⳱ 1.68 × 10−4 exp(−118 ± 12 kJ/RT) m/s1/2. The diffusion of nickel through the reaction zone toward Ti3SiC2 is the main controlling step in the bonding process. Joint strengths were determined through shear tests. The maximum shear strength of 121 ± 7 MPa, which is close to the shear strength of Ti3SiC2, has been obtained under the condition of 1000 °C for 10 min under 20 MPa.
I. INTRODUCTION
Ti3SiC2 is one of the nanolayered ternary ceramics Mn+1AXn, where M is a transition metal, A is an A-group (mostly IIIA or IVA) element, and X is C or N. It attracts considerable attention because of its unique combination of properties. The salient properties of this ceramic include low density, high strength, and elastic modulus, a high ratio of fracture toughness to strength, damage tolerance at room temperature, metallic electrical conductivity, good machinability, excellent thermal shock resistance, and oxidation resistance. These unusual combinations of the properties render it a candidate structural material for high-temperature applications.1–8 Although synthesis and properties such as mechanical properties and high-temperature oxidation resistance of Ti3SiC2 bulk material have been widely investigated, its application is still limited. Similar to other ceramics, the synthesis of bulk Ti3SiC2 with big dimensions and complex shapes is also difficult in practice. This limitation can be overcome by joining suitable components together to get the required dimensions.9 Therefore, studies on the joining of Ti3SiC2 with metals or ceramics are a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0290 J. Mater. Res., Vol. 21, No. 9, Sep 2006
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significant for promoting its applications. Gao et al.10 conducted the diffusion bonding of Ti3SiC2 with Ti-6Al-4V. Their results indicated that Ti3SiC2 could be bonded with Ti-6Al-4V in the temperature range from 1200 °C– 1400 °C, but the bending strength of the joint was about 100 MPa, only one-quarter of that of Ti3SiC2. Thus, more work on the joining of Ti3SiC2 is needed. Various bonding techniques on joining ceramic to metal or ceramic to ceramic have been developed in the last few decades.9–26 In this work, diffusion bonding is considered
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