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Abstract. The superalloy BC1 (trademark of HAYNES International, Inc.) is an alloy used in the production processes of organic acids at high temperature, refining industry and a wide variety of chemical applications using hydrochloric and sulfuric acids.The HYBRID-BC1 is an alloy composed essentially of 62% of nickel, 22% of molybdenum and 15% of chromium. Its matrix is austenitic and its structure is face-centered cubic.The aim of this work is to study the influence of heat treatment on the structural and mechanical properties of the nickel based alloy. Indeed, four temperatures were chosen 700°C, 800°C, 900°C and 1000°C for a treatment time of 3 hours.The final hardness of the alloys treated at 700°C, 800°C, 900°C and 1000°C is equal respectively to 47.25 HRF, 47 HRF, 47 HRF and 47.5 HRF. The images obtained by optical microscopy after the iso-thermal treatments showed the presence of carbides at the joints and inside the grains in several morphologies, discontinuous transformations and eutectic precipitates. The X-ray diffraction spectra done during over aging consist of peaks of the austenite phase and precipitates.
Keywords: Nickel-based alloy, thermal treatments, hardness, optical microscopy, X-ray diffraction.
1. INTRODUCTION
The large family of nickel-based alloys has been empirically developed over the last 60 years from a matrix consisting of nickel-chromium [1]. These austenitic alloys have a face-centered cubic structure which improved mechanical properties at high temperatures compared to alloys body-centered cubic structure [1].
The family B contains nickel-chromium based alloys characterized by good resistance to oxidizing environments [2].The alloys of the family C are Nickel-Chromium-Molybdenum based alloy that combine a good resistance to reducing and oxidizing environments [3].According to the manufacturer, the superalloy HYBRID-BC1 is an alloy used in applications even in the presence of various oxidizing impurities that neither the alloys of the family B and C can support.
The addition of aluminum protects the alloy against corrosion at high temperature by forming a layer of oxide Al2O3 [4]; a protective layer Cr2O3 is also formed due to the presence of chromium [5].The role of Silicone added in small proportion is to maintain these oxide layers [4].Molybdenum is a refractory element [6] and which can also drastically deagrades resistance to corrosion at high temperature for Nickel-based superalloys [4].
In industrial application, structural changes...