IARJSET ISSN (Online) 2393-8021 ISSN (Print) 2394-1588 International Advanced Research Journal in Science, Engineering and Technology ISO 3297:2007 Certified Vol. 4, Issue 6, June 2017 Copyright to IARJSET DOI10.17148/IARJSET.2017.4607 36 Cutting of 316L Stainless Steel Stents by using Different Methods and Effect of Following Heat Treatment on Their Microstructures Levent Oncel 1 , Ahmet Turan 2 , M. Ercan Acma 1 Metallurgical and Materials Engineering Department, Faculty of Chemical and Metallurgical Engineering, Istanbul Technical University, Maslak, Istanbul, Turkey 1 Chemical and Process Engineering Department, Faculty of Engineering, Yalova University, Yalova, Turkey 2 Abstract: In this study, effect of different cutting methods and following normalization heat treatment on microstructure of 316L stainless steel tubings were investigated. 316L stainless steel is the most commonly used material for coronary stent production. Tubings were cut with laser cutting, plasma cutting, oxy-fuel cutting, water jet cutting and electrical discharge machining methods. Cut tubings were characterized by using Scanning Electron Microscope (SEM). Separate samples were prepared for heat treatment operation. 316L stainless tubings were cut with same methods and same parameters. Normalization heat treatment was applied to the samples. Heat treated tubings were characterized by using Scanning Electron Microscope. When results were evaluated, it was seen that laser cutting gives the best results rather than that of other cutting methods in terms of homogeneous microstructure, smoothness of cutting surface, a microstructure without oxidation and distortion etc. Keywords: Biomaterials, Cutting, Heat Treatment, Microstructure, Stent, 316L. I. INTRODUCTION Implants are medical devices, which are introduced into human body to treat a disease, replace an organ or supply a function. Gold is the first known biomaterial and it was used in dentistry more than 2000 years ago by Romans, Chinese and Aztecs. Glass eyes and wooden teeth had been in common use through most of the recorded history [1]. When we look at the recent history and the present day, we see more advanced implants thanks to experiences gained from the previous implants and interdisciplinary studies. Today a wide variety of implants are produced. Implants like pacemakers, substitute heart valves, occluders, sternum wires, bare metal and drug eluting stents have great importance in the cardiology field [1,2]. Stenting is the most common method for treatment of clogged arteries. Stent is a small metallic mesh tube that has ability to expand. Stent is mounted on a balloon that is opened inside of the coronary artery to push back plaque and to restore blood flow. The stent is expanded to the desired diameter. Balloon is then deflated and removed. So, stent remains in the artery and keep the artery open [3]. Shaping of stents is the first step of the production process. It has patterns less than 100 μm, for this reason cutting operation should be carried out precisely. Stents on the current product market generally has strut width around 75-80 μm. Both sides of the strut will have the effects of the cutting process, so cutting should be done precisely to keep the microstructural change at the minimum level (Figure 1) [4,5]. Laser cutting is the most common method for cutting of stents. In this method, program is loaded to laser cutting machine. This program controls the timing of the laser beam and the movement of the metal tubing. Cutting method is very important to get the desired design of the stent. After the cutting operation, the microstructure next to the cutting area and the microstructure of the same area after the subsequent heat treatment have a critical importance on the properties of the stent [4,6]. Design parameters affect the mechanical properties of the stent. The effect of the design on the mechanical properties of the stent is simulated with a simulation software. Generally, a stent design includes struts and links. When balloon is expanded to desired diameter, mounted stent is also expanded. During this expansion, the angle between these struts increases, by this way struts provide homogenous distribution of plastic deformation. Links are the connectors between these struts [7].