TECHNICAL PAPER An Investigation on High-Temperature Oxidation and Hot Corrosion Resistance Behavior of Coated TLP (Transient Liquid Phase)-Bonded IN738-LC Reyhaneh Sahraeian 1 • Hamid Omidvar 1 • S. M. Mehdi Hadavi 2 • Sajad Shakerin 1 • Vahid Maleki 1 Received: 14 April 2018 / Accepted: 16 August 2018 Ó The Indian Institute of Metals - IIM 2018 Abstract Despite all achievements to improve nickel- based superalloy, these classes of alloys are still prone to degradation via high-temperature oxidation and hot corro- sion. Repairing damaged parts could decrease the life cycle, cost of equipment, and a transient liquid phase (TLP) bonding is a favorable method that has successfully been used for this purpose. One way to increase the lifetime of the repaired parts and the main body is to utilize protective coating. In the current study, aluminized coating was applied on IN738-LC which was first bonded by TLP process. Coating performance on the joint centerline compared to the other parts of the sample was investigated using a scanning electron microscope (SEM and FESEM) and X-ray diffraction method (XRD). The oxidation test result showed that coating provided less protection on the joint centerline due to coating’s chemical composition difference in this area: particularly Fe and Cr. XRD results showed that at the initial time of oxidation, all (a, c, d and h)-Al 2 O 3 were formed and by prolonged exposure were transformed to a-Al 2 O 3 . The hot corrosion test also proved that the joint centerline and the diffusion-affected zone were less resistant to the corrosion attack of 3Na 2 SO 4- ? NaCl salts and severity of damage in these zones were clearly distinguished from microscopic images. Keywords High-temperature oxidation Á Hot corrosion Á Pack cementation Á TLP bonding Á Ni-based superalloy 1 Introduction Gas turbine components made of nickel-based superalloys are exposed to extremely harsh operating conditions. Although all modification have been done in the chemical composition of Ni-based alloys during past decades [1, 2], these superalloys are still vulnerable to degradation by both mechanical and chemical factors [3]. The imminent dam- age besides the high price of new equipment is a factor which encourages companies to repair components in operation as long as possible. One way to achieve this goal is to protect these components by application of advanced coating, and another way is to repair damaged part if possible. In some cases, repair process requires detaching of the damaged section and inserting new one or restore the part instead [4–7]. Therefore, utilizing joining methods would be unavoidable for reattachment. Since Ni-based superalloys are susceptible to fusion zone and heat-affected cracking, industrial usage of conventional welding methods for joining or repairing are restricted [8]. Moreover, severe hot corrosion in the welded area has been reported by Indacochea et al. [9]. Nonetheless, transient liquid phase (TLP) bonding is a promising joining/repairing method for IN738-LC featuring near-ideal joints [10]. Considering gas turbine component in severe corrosive atmospheres, it is necessary that bonded parts possess enough resistance to & Reyhaneh Sahraeian sahraeian@aut.ac.ir Hamid Omidvar Omidvar@aut.ac.ir Sajad Shakerin sjdsh@aut.ac.ir Vahid Maleki vahidmaleki@aut.ac.ir 1 Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran 15875-4413, Iran 2 School of Materials Science and Engineering, Malek Ashtar University of Technology, P.O. Box 15875-1774, Tehran, Iran 123 Trans Indian Inst Met https://doi.org/10.1007/s12666-018-1390-0