Investigating the microstructure and properties of nickel base alloy 718 produced by additive manufacturing process with laser direct metal deposition method

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Investigating the microstructure and properties of nickel base alloy 718 produced by additive manufacturing process with laser direct metal deposition method

ارائه دهنده: Provider: Yeganeh ghahremani

اساتید راهنما: Supervisors: Dr. Sheikhi - Dr. Mazaheri

اساتید مشاور: Advisory Professors: Dr. Mahmood Moradi

اساتید ممتحن یا داور: Examining professors or referees: Dr.Esfahani - Dr.Pak

زمان و تاریخ ارائه: Time and date of presentation: 1401/12/16

مکان ارائه: Place of presentation: Amphitheater

چکیده: Abstract: Additive manufacturing is a new method for producing parts in various materials such as metal, polymer, plastic, etc., which is controlled by computer and creates three-dimensional parts by depositing materials in layers. Additive manufacturing of superalloys is used in various industries such as aerospace, transportation, defense, biomedicine, power plants, and repairing turbine blades. Inconel 718 is one of the common alloys for metal additive manufacturing and has a wide range of applications. In the present research, Inconel 718 superalloy powder was deposited on the steel substrate using direct laser metal deposition method and 1 kW fiber laser. In this process, variable input parameters are powder flow rate parameters, laser scanning speed, scanning pattern and other process parameters such as laser power, axial gas, powder carrier gas, lens placement, number of deposition layers, stopping time of successive deposition layers and waves. Constants were determined as fixed parameters. Eight experiments were performed by applying variable and fixed input parameters and samples were made using Inconel 718 powder and steel substrate. In this research, the effect of process parameters such as powder flow rate, scanning speed and scanning pattern on the microstructure, microhardness and height of the samples was investigated. An optical microscope was used to examine the structure of the sediment layers at low magnification, a field emission electron microscope was used to image the microstructure and chemical composition of the phases, and a microhardness device was used to measure the microhardness of different points of the deposited layers. In addition, the chemical composition of the powder was calculated by analyzing the inductively coupled plasma spectrometer and the height of the samples with Digimizer software. Microscopic investigations showed that several types of microstructures can be seen in the deposited layers. It was observed that in the lowest part of the layers, the microstructure is cellular, and moving upwards, the microstructure becomes cellular-dendritic, then columnar dendrites, and finally coaxial dendrites. This non-uniformity in the microstructure can happen due to the increase of subfreezing mixture from the bottom to the top of the samples. Investigations showed that Inconel 718 super alloy consists of different phases. The base phase is ϒ phase and other phases such as ϒ′′, ϒ′ and Lava phase are created in Inconel 718 alloy. Phase ϒ′ and ϒ′′ are the main phases of the amplifier. The hardness measurement of the samples showed that the microhardness of the samples is unevenly distributed, which can be justified by the fact that with the reduction of the powder flow rate, the thickness of the layers decreases, in which case each layer becomes the HAZ of the previous layer. converted and the hardness decreases. Also, with the increase in scanning speed, the HAZ area becomes smaller and the hardness of the samples increases. The highest average microhardness is 477 Vickers, which occurred at high powder flow rate and high scan speed. The calculation of the height of the samples showed that the height of the samples increases with the increase of the powder flow rate and the decrease of the scanning speed. The highest height of the samples is 5890 micrometers, which happened at high powder flow rate and low scanning speed. Investigations showed that the scanning pattern parameter had no significant effect on the microhardness and height of the samples.