Titanium-304L Stainless Steel Joining by Powder Metallurgical Uniaxial Pressing under Vacuum Conditions

M. Telli, R. Yamanoglu, H. Sanlı Kocaeli University, Metallurgical and Materials Engineering Department, 41380 Kocaeli, Turkey

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Ti-304L dissimilar metal joining was achieved by using powder metallurgical uniaxial pressing at 1000° for 10 minutes under vacuum. According to scanning electron microscope investigations, there were two different intermetallic layer formations rich in Fe, Ti and Ni content at joining interface. There were also some iron, nickel and chromium diffusion into titanium but limited Ti diffusion into 304L. For the studied sample dimensions, high residual stress appears as the result of big thermal expansion difference and large cool down step from high joining temperature to room temperature. Chemical bonding was found to be strong enough to prevent total delamination of joined Ti-304L sample, though cracking from surface defects at interface was observed. ANSYS 14 Multiphysics modelling has shown that residual stress levels were in fact high. For studied sample profiles, the 304L layer had residual maximum tensile principal stress around 332 MPa at the outer edge of the joining interface, Ti layer had lower residual minimal compressive principal stress around -290 MPa in the region close to the outer edge. Corresponding equivalent plastic strains were of the order of 0.0017 m/m for Ti layer and of the order of 0.011 m/m for 304L layer. Despite high residual stress levels, Ti-304L joining could be done at 1000° with powder metallurgical uniaxial pressing.

DOI:10.12693/APhysPolA.134.37 topics: Ti, 304L, dissimilar metal joining, interfacial reactions, powder metallurgy, residual stress strain modelling