The International Journal of Engineering and Science (IJES) || Volume || 7 || Issue || 7 Ver. I|| Pages || PP 71-78 || 2018 || ISSN (e): 2319 – 1813 ISSN (p): 23-19 – 1805 DOI:10.9790/1813-0707017178 www.theijes.com Page 71 Study Of Mechanical Properties And Microstructure Of Fe 3 Al / Bni-2 / Steel Brazed Joints M. M. Abdalla (1); Eltohamy.R. Elsharkawy (2); A. Kandil (3) (1) Material Sci. and Eng., Omar Al-Mukhtar University, Faculty of Eng., Al-Baidaa, Libya (2) Nuclear &Radiological Regulatory Authority, Cairo, Egypt. (3) Mining and Pet. Department, Faculty of Eng., Al-Azhar University, Cairo Egypt Corresponding Author: Eltohamy.R. Elsharkawy --------------------------------------------------------ABSTRACT---------------------------------------------------------------- Iron aluminides (Fe 3 Al) intermetallic and steel were joined successfully by vacuum brazing using of BNi-2 braze alloy. Brazing experiments were carried-out at bonding temperature 1040 o C and at different bonding time 2-20 minutes. Fe 3 Al/BNi-2/steel joints were thus formed. The microstructure features in the Fe 3 Al/BNi-2/steel joints were analyzed by a variety of characterization techniques such as optical microscope and scanning electron microscope (SEM) with energy- dispersive spectroscopy (EDS), electronic probe microanalysis (EPMA) and an X-ray diffractometer. The micro-hardness from Fe 3 Al to steel through BNi-2 braze alloy were measured with a Vickers microhardness. The shear strength of the Fe 3 Al/BNi-2/steel joints were evaluated with a shear test machine and the maximum shear strength of Fe 3 Al/BNi-2/steel joints was 496 MPa for joints bonded at bonding temperature of 1040 o C and bonding time of 5 minutes. The transition zones in the middle between the Fe 3 Al and the steel were obviously observed and the width of the transition zone was 21 μm. Diffraction Standards indicates that there were chromium boron (CrB); chromium boron(CrB 4 ); aluminum nickel (AlNi 3 ); aluminum iron (FeAl); Iron aluminides (Fe 3 Al); and nickel silicon (NiSi) phases are present at the fracture surfaces of the Fe 3 Al/BNi-2/steel joint and aluminum iron silicon (Al 0.3 Fe 3 Si 7 ); nickel (Ni); Iron aluminides (Fe 3 Al) phases are present at the Fe 3 Al/BNi-2/steel joint surface perpendicular to the joint transition zone. The microhardness values at the transition zone increased from about 211 HV close to steel side to about 451 HV close to BNi-2 side. Along the BNi-2 braze alloy, the microhardness was about 608 HV and when reached the BNi-2/ Fe 3 Al transition zone, the microhardness decreased to 347 HV close to Fe 3 Al. Along the BNi-2 brazed alloy was higher than that at the Fe 3 Al this indicates that there was possible formation of hard and brittle phases at the joint transition zone and at the BNi-2, since the fracture occurred along the BNi-2/ Fe 3 Al transition zone. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 28-06-2018 Date of acceptance: 13-07-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Nickel base braze alloys both have good corrosion resistance and creep strength, so it was selected as filler metal. BNi-2 has high creep strength and low liquidus temperature among all Ni base braze alloys, the solidus and liquidus temperatures of this alloy are 970 and 1000 o C, respectively. Therefore, BNi-2 was chosen as a brazing filler metal in joining Fe 3 Al by infrared brazing and its chemical composition in weight percent was 7.0 Cr, 3.1 B, 4.5 Si, 3.0 Fe, 0.06C, and Ni balance [1,2]. Joining of Fe 3 Al is performed by using infrared vacuum brazing using BNi-2 as the brazing filler alloy. The species and morphology of phases in the brazed joint are extensively examined. Many transient phases, including: (Ni,Fe) 3 Al, (Ni,Fe) 3 (Si,Al), (Fe,Ni,Cr) 3 B and BCr, were observed after infrared brazing. With increasing the homogenization time of the brazement at 1000 o C, the stoichiometry of both (Ni,Fe) 3 Al and (Ni,Fe) 3 (Si,Al) phase has changed into (Ni,Fe) 2 Al and (Ni,Fe) 2 (Si,Al). Most of BCr and (Fe,Cr,Ni) 3 B phases can be dissolved into the Fe 3 Al matrix during homogenization of the brazement, so the amounts of the chromium boride and (Fe,Ni,Cr) 3 B phases are decreased with the time increment of homogenization [3,4]. Iron aluminides (Fe 3 Al) intermetallic and steel were joined successfully by vacuum brazing using of B- Ni83 braze alloy. Brazing experiments were carried-out at bonding temperature 1040 o C and at different bonding time 2-20 minutes. Fe 3 Al/B-Ni83/steel joints were thus formed. The maximum shear strength of Fe 3 Al/B- Ni83/steel joints was 470 MPa for joints bonded at bonding temperature of 1040 o C and bonding time of 5 minutes[5,6]. Diffraction Standards indicates that there were chromium nickel (Cr 1.12 Ni 2.88 ); Awaruite (FeNi 3 ); iron nickel-alpha-(Fe 10.8 Ni); nickel boron (Ni 3 B); chromium boron (CrB) and iron nickel (Fe 0.64 Ni 0.36 ) phases are present at the fracture surfaces of the Fe 3 Al/B-Ni83/steel joint and Iron chromium (FeCr); nickel (Ni); aluminum iron (FeAl) and iron aluminide (Fe 3 Al) phases are present at the Fe 3 Al/B-Ni83/steel joint surface perpendicular to the joint transition zone [7].