Heat Treatment and Mechanical Properties of 316L Stainless Steel Produced by Additive Manufacturing Process

Abstract

316L stainless steel is a type of molybdenum bearing austenitic stainless steel. This steel has a lower carbon and higher molybdenum of percentage than 316 stainless steel. The maximum carbon content in this steel composition is 0.03%, which minimizes the precipitation of carbide during welding. This steel is characterized by high creep resistance, excellent corrosion and pitting resistance, and excellent formability, etc. As a result, this steel is widely used in many industries and commerce, especially in shipbuilding industry and marine.316L stainless steel parts are produced by traditional methods like forging, casting or extrusion, etc. However, these methods do not allow manufacture parts with complex shapes, and the product has to be weld or machined into final form. Therefore, the production processes are time consuming and costly. In the present, a new technology has solved the issue to an extent in certain application regarding to complex shapes and monolithic structure. This is additive manufacturing (AM) technique. However, there are many limitations in the understanding structure and mechanical properties of additive manufactured components. AM is a new technology that fabricates three-dimensional objects through using a computer-aided design (CAD) model or a digital 3D mode [3]. Powder bed fusion (PBF) process is one of the main metallic AM technologies, during which one or multiple laser manner [4]. PBF process spread powdered material over the previously joined layer, ready for processing of the next layer hence the manufacturing is discrete rather than continuous [5]. Each layer is then sequentially bonded on top of each other. The quality of product fabricated by PBF method will depend on the parameters such as laser scanning speed, laser power, layer thickness, hatch distance, laser orientation and build-direction. Therefore, PBF process is a parameter sensitive process. This study aims to better understanding the effect of process parameters and the heat treatment on microstructure and mechanical properties of 316L stainless steel specimens produced by PBF process. Tensile and Vickers hardness test were conducted to study the evolution in mechanical properties after applying different experimental conditions.