Functionally graded material (FGM) is an advanced material that illustrates the number of properties in a single component. To develop FGM, it is very important to study each component gradient separately to understand the properties and their behaviour. This paper presents the study of the properties of deposited blocks of the different gradients of Inconel 625 (IN625) and stainless steel 304L (SS304L) (25% IN625 + 75% SS304L, 50% IN625 + 50% SS304L, 75% IN625 + 25% SS304L, and 100% IN625) by a laser directed energy deposition technique. Various tests were performed to understand its mechanical, metallurgical, and chemical behaviour. Deposited samples were heat-treated and then optical microscopy and microhardness were measured and compared to untreated ones and results found to be comparatively improved.
Purpose
Prior to manufacturing, designing plays a vital role in the selection of materials and other design parameters. Therefore, during the deposition of materials, substrate materials provide support and affect the microstructure of the deposits, which may not be desirable in the manufactured product. Hence, the main purpose of the study is to analyse the behaviour of the microstructure at the interface of deposited material and substrate.
Design/methodology/approach
In this study, two blocks of Inconel 625 (IN625) and Stainless steel 304L (SS304L) metal powders were deposited on an SS304L substrate using laser directed energy deposition (DED) technique. Deposited blocks comprised 50% IN625 + 50% SS304L or 100% IN625. After deposition, microstructural behaviour at the interface of the deposits and substrates was analysed using different tests such as optical microscopy (OM), microhardness testing, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). An improvement in microstructure was proposed by performing heat treatment of the deposited sample.
Findings
Formation of martensite and precipitates at the interface of the deposit and substrate was observed. Formation of martensite and precipitates such as α, carbide and δ phases were observed in OM and SEM images. Due to the formation of these phases, interface regions showed a peak in the hardness graphs. Post-heat treatment of the samples was one of the solutions to resolve these issues.
Originality/value
This paper suggests the formation of a heat-affected zone (HAZ) at the interface of the deposit and substrate, which may negatively affect the overall utility of the deposited part. The properties of the HAZ were investigated. To suppress these detrimental effects, post-heat treatment of the deposited sample was performed, and the samples were further analysed. The post-heat-treated samples exhibited as reduction in HAZ thickness and had more uniform hardness throughout the cross-section compared with the untreated samples.
This book presents the abstracts of the papers presented to the Online National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020 (RDMPMC-2020) held on 26th and 27th August 2020 organized by the Department of Metallurgical and Materials Science in Association with the Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, India.
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