1 Tribological Evaluation of an Optical Fiber Laser Marked Stainless Steel for Biomedical Applications Eurico Felix Pieretti 1,2 , Renato Altobelli Antunes², Maurício David Martins das Neves 1 1 Nuclear and Energy Research Institute (IPEN-CNEN), Av. Prof. Lineu Prestes, 2242, São Paulo - SP, 05508-000 – Brazil ² Federal University of ABC (UFABC), Av. dos Estados, 5001, Santo André – SP, 09210-580 - Brazil Abstract The effect of laser marking process on the tribological behaviour of ISO 5832-1 austenitic stainless steel (SS) on the friction coefficient and wear volume using ball-cratering wear tests was evaluated in this work. The laser marking process was carried out with a nanosecond optical fiber ytterbium laser at four different pulse frequencies. For comparison reasons, surfaces without laser treatments were also evaluated. A phosphate buffer solution (PBS) was used as lubricant. The wear tests were carried out during 10 min with PBS drip, solid spheres of AISI 316L SS with 1 inch in diameter and of 52-100 chrome steel, with 2 mm in diameter, were used as counter-bodies. The results indicated that the tribological behaviour is influenced by the laser marking process parameters used, and the wear rate is dependent of the normal force and the type of sphere. Keywords: Orthopaedic Implants, laser, wear. 1. Introduction Biomaterials, due to corrosion and even friction against implantable components, bones or other body parts can detach particles, which coming into contact with bodily fluids, are able to be placed in locations far from the removed source causing complications to the patients [1]. Detached particles released from the degradation process may move inertly, through tissue and/or circulatory system or can be actively transported [2, 3], compromising the biocompatibility. The ISO 5832-1 stainless steel (SS) is one of the metallic materials used for implants manufacture, because of its mechanical and electrochemical properties and low cost [4, 5]. The laser technique is commonly used for identification of the metallic implantable medical device [4-7]. This process involved temperatures above 1600 ºC, which melts the stainless steel surfaces. In the biomaterials’ field for implantable medical or dental devices, tribological tests are of great value in providing an estimate of the normal, tangential and frictional forces in relation to the volume of material that can be detached from the surface, migration and housing of particles. The micro-scale abrasion test (or ball-cratering wear test) is a useful method to investigate the wear resistance of various materials [8-10]. The ball-cratering wear test has gained large acceptance at universities and research centers and is widely used in studies focusing on the abrasive wear behavior of dissimilar materials [11-15]. The principle of this wear test consists in a rotating ball that is forced against the specimen being tested and a lubricant, PBS in this case, is supplied between the ball and the specimen during the experiments. The aim of the ball-cratering wear test is to generate “wear craters” on the specimen. The wear volume ( V) may be determined as a function of b, using Equation 1 [11], where R is the radius of the ball. R d π V 64 4  (1) Wear tests conducted under the ball-cratering technique present advantages in relation to other types of tests, because it can be performed with normal forces (N) and rotations of the sphere (n) relatively low (N < 0.5 N and n < 80 rpm) [16-20]. The aim of this work was to evaluate the tribological behaviour of the ISO 5832-1 austenitic stainless steel (SS), widely used for biomedical applications, marked via an optical fiber laser process with four different pulse frequencies, using two ball-cratering wear methods.