Effect of Specific Energy Input on Microstructure and Mechanical Properties of Nickel-Base Intermetallic Alloy Deposited
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AN extensive demand for materials with improved properties in terms of their hardness and their resistance to wear, corrosion, and oxidation has been the driving force for the development of various surface hardfacing techniques and materials. Recently, laser cladding has been explored for the deposition of less diluted and fusion-bonded thick and thin metallic coatings on a wide variety of metallic substrate materials with a low heat input. Numerous studies have shown superior characteristics of hardfacing alloys deposited by laser cladding as compared with other conventional surfacing techniques.[1–4] Laser treatments have also been employed for the densification of thermally sprayed metal alloy clad layers.[5,6] The laser-cladding technique has the advantage of depositing a controlled thickness of the clad material on a selected area of the substrate. Cobalt- and nickel-base Tribaloy intermetallic alloys have been developed as an excellent corrosion- and
REENA AWASTHI, SANTOSH KUMAR, KAMLESH CHANDRA, B. VISHWANADH, C.S. VISWANADHAM, and D. SRIVASTAVA, Scientific Officers, and G.K. DEY, Head, are with the Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400085, India. Contact e-mails: [email protected]; [email protected] R. KISHORE, Scientific Officer, is with the Post Irradiation Examination Division, Bhabha Atomic Research Centre. Manuscript submitted August 22, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS A
wear-resistant material over a wide range of temperatures and environments.[7] Tribaloy alloys are strengthened by the presence of a large volume fraction of a hard intermetallic Laves phase in a much softer solid-solution phase or a eutectic phase mixture.[8–11] Among the constituent elements of Tribaloy, chromium is used to enhance corrosion resistance and strengthen the solid solution, whereas molybdenum and silicon are used to impart wear resistance by forming the intermetallic Laves phase, and nickel or cobalt provide a tough matrix. Laves phases have topologically closed-packed structures,[12] which hinder the movement of dislocations, making them very hard and rather brittle.[13] Therefore, Tribaloys are seldom applied in bulk form but rather are applied as coatings.[14,15] Cobalt-base Tribaloy alloys have been extensively studied as welded and clad overlays by laser-cladding technique[16–18] as well as thermal spray technique.[19–21] However, the high cost and scarcity of cobalt led to the development of cobalt-free hardfacing alloys. Furthermore, in the nuclear industry, the use of cobalt-base alloys is limited due to the induced activity of long-lived radioisotope Co60 formed. These difficulties led to the development of various nickel and iron-base alloys to replace cobalt-base hardfacing alloys.[22,23] Tribaloy T-700 is cobalt-free nickel-base alloy, described as an alternative to the cobalt-base Tribaloy for nuclear applications involving wear, corrosion, and hightemperature resistance.[24] It was demonstrated that a nickel-base alloy having composition, Ni-32 wt pct
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