Microstructures and hardness properties of laser clad Ni base two-phase intermetallic alloy coating
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Takuto Yamaguchi Osaka Research Institute of Industrial Science and Technology, Izumi, Osaka 5941157, Japan
Satoshi Semboshi Trans-Regional Corporation Center, Institute for Materials Research, Tohoku University, Sakai, Osaka 5998531, Japan
Hideki Hagino Osaka Research Institute of Industrial Science and Technology, Izumi, Osaka 5941157, Japan
Takayuki Takasugia) Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 5998531, Japan (Received 18 April 2017; accepted 9 August 2017)
The two-phase Ni3Al and Ni3V intermetallic alloy laser clad on substrate of SUS304 was evaluated by hardness measurement, scanning electron microscopy, electron probe microanalyzer and transmission electron microscopy observations, focusing on the effect of post annealing after laser irradiation. The laser clad coating layer was diluted with approximately 5.4 at.% Fe and 1.6 at.% Cr stemming from the substrate. In the as-clad coating layer, the inhomogeneous eutectoid microstructure due to incomplete phase separation into two intermetallic phases Ni3Al and Ni3V took place. The hardness in the as-clad coating layer was lower than that in post annealed coating layers. In the coating layer annealed at 1553 K for 5 h, a dual two-phase microstructure composed of the primary cuboidal Ni3Al surrounded by the channel regions in which the major constituent is the Ni3V phase was observed, indicating that the complete eutectoid microstructure was developed. In the coating layer annealed at 1248 K for 24 h, the developed microstructure was lamellar-like one composed of the Ni3Al and Ni3V phases. The hardness in the coating layer annealed at 1248 K was the highest in the coatings observed in this study.
I. INTRODUCTION
The present authors have recently developed a new type of two-phase intermetallic alloys composed of Ni3Al (L12: a 5 0.3572 nm) and Ni3V (D022: a 5 0.3542 nm and c/ a 5 2.036) phases.1–7 The microstructure is composed of Ni3Al and Ni solid solution (A1: fcc) phases at a high temperature, and the Ni solid solution phase is decomposed into a (Ni3Al 1 Ni3V) microstructure by a eutectoid reaction at a low temperature (;1273 K) as shown in Fig. 1.8,9 The so called dual two-phase microstructure is thus comprised of whole intermetallic (ordered) phases with high structural coherency, leading to high microstructural stability at a high temperature. The dual twophase intermetallic alloys have been found to exhibit excellent strength and hardness at high temperatures due to their fine, coherent, and stable microstructure and thereby are expected to be used for high-temperature Contributing Editor: Mathias Göken a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.352
structural and wear-resistant applications such as hightemperature dies, molds, and tools. For wear-resistant applications, coating processes such as thermal spraying and cladding by welding have been practically applied. Recently, laser cladding has been widely used as a surface modification processing becau
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