Diffusion Bonding of 17-4 Precipitation Hardening Stainless Steel to Ti Alloy With and Without Ni Alloy Interlayer: Inte
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INTRODUCTION
THE dissimilar material joint of Ti alloy and precipitation hardening stainless steel (PHSS) is potentially applied for attractive products for various applications. For instance, a golf club head can be made by a Ti alloy striking plate and a PHSS body.[1,2] The conventional fusion welding method is not suitable for joining them due to a high possibility of the brittle intermetallics formation in the weld zone, in addition to the difference in melting points of these two materials. Furthermore, Ti alloy and stainless steel have wide differences in their physical properties. In particular is the mismatch of their coefficients of thermal expansion with Ti alloy and PHSS having coefficient of thermal expansion 3.36 9 10 8/K and 1.08 9 10 5/K, respectively, which results in large residual stress in the joints after processing.[3] Diffusion bonding has proved to be a near net shape forming process for simultaneous joining and manufacturing of Ti alloy materials without gross macroscopic distortion and with minimum dimensional S. KUNDU, Assistant Professor, G. ANAND, Post-Graduate Student, and S. CHATTERJEE, Professor and Director of Research and Consultancy, are with the Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711103, West Bengal, India. Contact e-mail: [email protected], [email protected] Manuscript submitted November 25, 2011. Article published online November 30, 2012 2196—VOLUME 44A, MAY 2013
tolerances, as Ti alloy exhibits both the superplasticity and diffusion bonding under the same conditions.[4–6] The literature reports that the intermetallic phases were formed at the diffusion interface of the transition joint consisting of Ti/Ti alloy and steel/stainless steel, which deteriorates the bond strength of the transition joints.[7–19] In the case of diffusion bonding of dissimilar materials, an interlayer inserted between substrates is often necessary to prevent the formation of intermetallic compound and to reduce the residual stress in the joints.[2,20] In an earlier investigation, the present authors improved the strength and ductility properties of diffusion-bonded joints between commercially pure titanium and 304 stainless steel using pure Ni as an intermediate material and achieved the tensile strength of the joint which was comparable with the strength of commercially pure titanium.[21] The literature reports that a shear strength of ~148 MPa was obtained for diffusion-bonded Ti-6Al-4V and 304 stainless steel web joint when processing was carried out at 1123 K to 1153 K (850 C to 880 C) for 10 to 20 minutes under 10 to 15 MPa load using a 30-lm-thick pure Ni interlayer.[22] However, direct bonding of these two dissimilar materials results in a lower bond shear strength of ~72 MPa.[23] In an earlier investigation, Ti alloy to 17-4 PHSS joint was carried out by a brazing technique and a maximum shear strength of ~233 MPa had been achieved at 1123 K (850 C) for 180 seconds using a 10-lm-thick (72Ag-28Cu in wt pct) braze alloy.[
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