Effect of Solidification Mode on Microstructure and Mechanical Properties of AISI420 Steel to SAF2507 Steel Dissimilar J
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Effect of Solidification Mode on Microstructure and Mechanical Properties of AISI420 Steel to SAF2507 Steel Dissimilar Joint Produced by Transient Liquid Phase M. Jafari1 · M. Rafiei1 · H. Mostaan2 Received: 19 February 2019 / Accepted: 28 July 2019 © The Korean Institute of Metals and Materials 2019
Abstract In this investigation, the microstructure and mechanical properties of AISI420/SAF2507 dissimilar joint produced by TLP process were investigated at different bonding times. For this purpose, TLP process was carried out in a vacuum furnace at 1050 °C using BNi-2 interlayer. The microstructure of different areas of the joint was evaluated by optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. Also, the mechanical properties of the bonded samples were studied using microhardness and shear-tensile tests. It was found that isothermal solidification was completed after 60 min of bonding time. The width of DAZ in SAF2507 steel side was greater than that of AISI420 steel side at all bonding times owing to the easier volume diffusion of boron in to the fully austenitic structure of AISI420 steel as compared with dual crystal structure of SAF2507 steel. At bonding time of 60 min, by regarding the more time for diffusion as compared with 1 min, boride compounds dissolved in the base metals and were discontinued. Thus, the aggregation of boride compounds decreased and as a result the microhardness decreased. In fully isothermal solidification sample, due to the lack of eutectic and intermetallic compounds and creating a homogenous joint (γ-Ni phase), the strength increased. In fact, transformation of athermal solidification to isothermal solidification led to the increase of the joint strength. Keywords AISI420 · SAF2507 · TLP bonding · Microstructure · Mechanical properties
1 Introduction In many cases, when corrosion resistance in reduction environments, strength, hardness, high wear resistance and keep sharp edges in pieces are important, martensitic stainless steels are used. These steels are magnetic and have ability to obtain variable range of hardness. The corrosion resistance
* M. Rafiei [email protected] M. Jafari [email protected] H. Mostaan [email protected] 1
Advanced Materials Research Center, Department of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
Department of Materials and Metallurgical Engineering, Faculty of Engineering, Arak University, Arak 38156‑8‑8349, Iran
2
of theses steels is weaker as compared with ferritic and austenitic stainless steels [1]. Nowadays, martensitic stainless steels due to the high corrosion resistance in reduction environments are widely used in oil industries and power plants. Also, these alloys are used in thermal generators due to maintaining high temperature strength [1]. Resistance to corrosion and thermal and mechanical shocks made of these steels good candidate to produce turbine blades, internal parts of industrial valves and especially as a best choice for producing
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