Effect of Joining Atmosphere in Transient Liquid Phase Bonding of Inconel 617 Superalloy
- PDF / 4,324,283 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 37 Downloads / 219 Views
INCONEL 617 (UNS N06617) is a solid solution-strengthened Ni-base superalloy, which consists of high amounts of solid solution elements (Mo, Cr, and Co). This superalloy has an exceptional combination of excellent oxidation resistance, superior mechanical properties, and high-temperature phase stability above 980 C.[1] This superalloy is used in power generation parts, industrial turbine, aerospace, and nuclear industry.[2,3] In the hot section of gas turbines, there are some components such as mixing chamber and hot gas inner casing that are manufactured from Inconel 617.[4] Fusion welding is the most widely used technique for joining parts made of Inconel 617. Cracking in the heat-affected zone (HAZ) before and after post-weld heat treatment is a common problem during fusion welding.[5] The material of Inconel 617 is very sensitive
H. ESMAEILI is with the Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT), Hafez Avenue, P.O. Box 15916-34311, Tehran, Iran, and also with the Mapna Turbine Engineering and Manufacturing Co., P.O. Box 3167643954, Tehran, Iran. S.E. MIRSALEHI and A. FARZADI are with the Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (AUT). Contact e-mail: [email protected] Manuscript submitted March 14, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
to the hot cracking especially in the HAZ. Therefore, during repair of these parts, complete HAZ removal of the welding joints is mandatory.[6] Repair of weld line more than two times is forbidden, due to precipitation of carbides in grain boundaries and permutation of structure after long-time service.[7] However, the increase in cost of superalloys and the high cost of manufacturing turbine components encourage the application of repair techniques rather than replacing failed parts to restore structural integrity.[8] Transient liquid phase bonding (i.e., diffusion brazing) solves all the above problems occurred during repair by welding. In this process, considering its low temperature, there is no melting in the base metal, and also simultaneous execution of several joints and implementation of complex joints can be possible. These characteristics of TLP bonding make it suitable for repair of gas turbine connections.[9] In the TLP bonding, a filler metal is placed between the base metals to reduce the bonding time. The operation is performed at a temperature lower than the solidus temperature of base metal and higher than the liquidus temperature of filler metal.[10] Normally, the process comprises three main stages: base metal dissolution, isothermal solidification, and homogenization of bonding zone.[11] The change in composition of the joints causes the joint to isothermally solidify.[12] However, if the bonding time is not sufficient for complete isothermal solidification, formation of
eutectic constituents could occur along the joints.[13] The homogenization heat treatment also improves the joint quality because of avoiding the formation of brittle phases.[14] The most
Data Loading...
