Laser Powder Bed Fusion Processed IN713-LC: Efforts to understand Cracking Mechanism Microstructure and Mechanical Properties

Abstract

Laser powder bed fusion (LPBF) is a technique that is used to manufacture the parts with high relative density and mechanical properties as well as to that of conventional approaches i e casting As the complex interaction between the laser and the powder in LPBF it has some flaws like pores micro-cracks and distortion during the built Inconel-713LC is a low carbon (LC) nickel-based superalloy generally produced by casting which is widely used in hot section components of gas turbine engines The selection of materials for gas turbines is critical to obtain high efficiency and reliability especially for the components located in the high-temperature service section where the flow of hot gases imposes severe operating conditions To withstand the loading conditions at high temperatures (500–915?C) it’s considered as a non-weldable alloy as it has a high percentage of Al+Ti compared to that of Inconel 718 This study focuses on the mechanical properties microstructure and phases of IN713LC for the as-built specimen and after the heat-treatment In this study experimental results show that the tensile strength and elongation of LPBF printed IN713LC tensile bar are higher than those made by casting The yield strength of 791 MPa the ultimate strength of 995 MPa elongation of 12% and relative density of the specimen approximately 99 98% is achieved The crack density is also reduced to a lower number to 0 11% per mm? It’s concluded that there are two kinds of micro-cracks one is called solidification cracking which due to the composition effect and the other is ductility dip cracking (DDC) which is due to reheating of the subsequent layer because of grain boundary slides and causes micro-cracking Also it’s concluded that heat treatment of IN713LC processed by LPBF is as it reduces mechanical properties There are two possible reasons for that one is an increase of the grain size after heat treatment and the other possible reason is strain age cracking (SAC) which occurs in Ni-based after the heat treatment as it causes more cracks for non-weldable alloys or increases the size of already existing cracks According to [1] Hot Isostatic Pressing (HIP) is the possible way to improve the mechanical properties as it could close the cracks and also close the small pores that would cause a reduction in mechanical properties

Date of Award	2021
Original language	English
Supervisor	Yu-Lung Lo (Supervisor)