Corrosion Characteristics of Ni-Based Hardfacing Alloy Deposited on Stainless Steel Substrate by Laser Cladding
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I.
INTRODUCTION
WEAR and corrosion are the most common surface-initiated failure mechanisms for the components working under aggressive conditions. When components are exposed to corrosion environments, combined effects of corrosion and wear are much more detrimental than those caused by corrosion or wear alone.[1,2] In order to improve wear and corrosion resistance of the surface, a large variety of hardfacing alloys, including cobalt (Co), nickel (Ni) and iron (Fe)-based, have been developed and explored, by depositing on various substrates.[3,4] Of these hardfacing alloys, some alloys provide excellent wear resistance but poor resistance to
REENA AWASTHI, GEOGY ABRAHAM, SANTOSH KUMAR, NACHIKET KESKAR, R.P. KUSHWAHA, R. TEWARI, D. SRIVASTAVA, and G.K. DEY are with the Material Science Division, Laser Materials Processing Section, Bhabha Atomic Research Centre, S-63 A, South Site, Mumbai, Maharastra 400085, India. Contact e-mail: [email protected] KAUSTAVA BHATTACHARYYA is with the Chemistry Division, Bhabha Atomic Research Centre, Mumbai, India. RAMANA RAO is with the Materials Characterisation Division, Nuclear Fuel Complex, Hyderabad, India. Manuscript submitted September 8, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
corrosive environments (such as carbon containing Fe-based hardfacing alloys, metal/ceramic composites to name a few) and vice-versa (Ni-based alloys such as Inconel and Monel). Generally, increase in hardness and wear resistance of the hardfacing alloy is associated with the reduction in corrosion resistance.[5] This behavior has been attributed to the fact that most of the materials derive their wear resistance from the presence of a hard phase (carbide, boride, or intermetallic phase) dispersed in a relatively more ductile eutectic or solid solution matrix. The presence of multiphases in hardfacing alloys with different compositions may sometime lead to preferential partitioning of some of the corrosion-resistant elements such as chromium (Cr) in one of the phases and make the other phase prone to corrosion. Generally, carbide containing wear-resistant hardfacing alloys, most specifically metal/ceramic composites (e.g., WC-Co) is not corrosion-resistant.[6] Generally, the susceptibility of Co binder to chemical attack limits the corrosion resistance of most commonly used Co-based carbide containing hardfacing alloys. The corrosive media dissolve the Co binder from the matrix, and thus a weak, unsupported skeleton of tungsten carbide grains left behind gets abraded away easily.[6]
Co- and Ni-based Tribaloy series of intermetallic alloys, containing 32Mo, 15Cr, and 3Si (wt pct) as alloying elements, exhibit their superiority over other hardfacing alloys in terms of their overall resistance to both wear and corrosion over a wide range of temperatures [~1073 K to 1273 K (~800 C to 1000 C)].[7–9] These alloys are primarily strengthened by Mo-rich intermetallic Laves phase dispersed in a Co- or Ni-based gamma solid solution or a eutectic matrix.[10–12] Ni-based intermetallic Laves phase all
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