ISSN: 1402-1757 ISBN 978-91-7439-XXX-X Se i listan och fyll i siffror där kryssen är LICENTIATE T H E SIS Department of Engineering Scienceand Mathematics Division of Machine Elements Jorge Rituerto Sin Investigation of Hafnium for Biomedical Applications of Hafnium for Biomedical Rituerto Sin Investigation Jorge ISSN: 1402-1757 Investigation of Hafnium ISBN 978-91-7439-680-5 (print) ISBN 978-91-7439-681-2 (pdf) for Biomedical Applications Luleå University of Technology 2013 Corrosion and Tribocorrosion in Simulated Body Fluids Jorge Rituerto Sin INVESTIGATION OF HAFNIUM FOR BIOMEDICAL APPLICATIONS Hf 40 cps /eV 20 Hf Hf C Hf O Hf Hf Hf Hf Hf Hf 0 12345678910keV Corrosion and Tribocorrosion in Simulated Body Fluids JORGE RITUERTO SIN Luleå University of Technology Department of Engineering Science and Mathematics Division of Machine Elements Cover figure: Schematic representation of an atom of hafnium. Title page figure: Energy dispersive X-Ray spectroscopy (EDX) spectrum of hafnium. INVESTIGATION OF HAFNIUM FOR BIOMEDICAL APPLICATIONS Corrosion and Tribocorrosion in Simulated Body Fluids Copyright c Jorge Rituerto Sin (2013). This document is freely available at http://www.ltu.se or by contacting Jorge Rituerto Sin, [email protected] This document may be freely distributed in its original form including the cur- rent author’s name. None of the content may be changed or excluded without the permission of the author. Printed by Universitetstryckeriet, Luleå 2013 ISSN: 1402-1757 ISBNISBN: 978-91-7439-680-5 (print) ISBN 978-91-7439-681-2 (pdf) Luleå 2013 Luleå 2013 www.ltu.se Preface The work presented in this Licentiate thesis has been carried out at the Division of Machine Elements at Luleå University of Technology (Luleå, Sweden) and at the Institute of Engineering Thermofluids, Surfaces and Interfaces (iETSI) (Leeds, UK). This research has been funded by the European Regional Devel- opment Fund through the Centrum för medicinsk teknik och fysik (CMTF) and Kempe Stiftelserna. The Swedish Research School in Tribology is acknowl- edged for travel funding. I would like to thank my supervisors Associate Professor Nazanin Emami, for giving me the opportunity of working on this project, and Professor Anne Neville, for her valuable help and guidance. I would also like to thank Dr. Xinming Hu for his input to my work. Thanks go to Martin Lund and Tore Serrander for their assistance in the lab and Lars Frisk for valuable help with sample preparation. I am grateful to my friends and colleagues at Leeds University, especially James Hesketh for long discussions about tribocorrosion and for his help in the lab. I would also like to thank all my friends and colleagues at the Divi- sion of Machine Elements at Luleå University of Technology for providing a friendly and enjoyable place to work. I would especially like to express my gratitude to Gregory Simmons for his valuable feedback on my manuscripts and Silvia Suñer for all her support and advice that help me to improve every day. Finally, I would like to thank my family for endless support and encourage- ment. Abstract Metals have excellent properties, such as high strength, ductility and tough- ness, which make them the material of choice for many biomedical applica- tions. However, the main drawback of metals is their general tendency to cor- rode, which is an important factor when they are used as biomaterials due to the corrosive nature of the human body. Titanium and titanium alloys are widely used in biomedical devices due to their excellent corrosion resistance and good biocompatibility. However, one of the disadvantages of titanium is its low wear resistance. Hafnium is a passive metal with a number of interesting properties, such as high ductility and strength, as well as resistance to corrosion and mechanical damage. Previous studies have shown that hafnium has good biocompatibility and osteogenesis. However, the behaviour of hafnium in biological environ- ment has not been studied in great depth. Furthermore, little is known about the resistance of the passive layer under wear-corrosion conditions and the ef- fect of proteins on its corrosion and tribocorrosion behaviour. The overall goal of this study is to assess the potential of hafnium for use in biomedical applications. The aim of this work is to investigate the corrosion resistance of hafnium in simulated body fluids as well as its behaviour in wear corrosion and fretting corrosion conditions. The results showed that hafnium presents a passive state in the presence of proteins and its oxide layer provides high protection to corrosion. In addi- tion, although the passive layer could be disrupted due to wear and fretting, increasing the corrosion of the metal, it was rapidly rebuilt when the damaging ceased. On the other hand, the main drawback of hafnium was its tendency to suffer from localised corrosion. Although the formation of corrosion pits was retarded in the presence of proteins, it was drastically increased when hafnium was scratched or subjected to fretting. Appended Papers [A] J. Rituerto Sin, X. Hu, N. Emami. Tribology, Corrosion and Tribocorrosion of Metal-on-Metal Implants. Published in Tri- bology - Materials, Surfaces and Interfaces, 2013, 7(1), 1-12∗. Presented at the International Conference on BioTribology, September 18-21, 2011, London, UK. ∗Reprinted with permission of Maney Publishing and Tribology - Ma- terials, Surfaces and Interfaces. Permission to reprint this material is gratefully acknowledged. [B] J. Rituerto Sin, A. Neville, N. Emami. Corrosion and Tribocor- rosion of Hafnium in Simulated Body Fluids. Submitted for journal publication. Presented at the 9th World Biomaterials Congress, June 1-5, 2012, Cheng- du, China. [C] J. Rituerto Sin, A. Neville, N. Emami. Fretting Corrosion of Hafnium in Simulated Body Fluids. To be submitted. Presented at the 3rd International Tribology Symposium of IFToMM, March 19-21, 2013, Luleå, Sweden. Contents I The Thesis 1 1 Introduction 3 1.1 The need for biomaterials . .................. 3 1.1.1 Types of biomaterials .................. 4 1.2 Metallic biomaterials ...................... 5 1.2.1 Titanium and titanium alloys . ............ 7 1.2.2 Possibilities of hafnium ................ 8 1.3 Tribocorrosion of metallic implants . ............ 10 1.3.1 Corrosion of implant materials . ............ 10 1.3.2 Wear of implant materials . ............ 11 1.3.3 Case study: Tribocorrosion of Metal on Metal implants 12 2 Objectives 15 3 Materials and Methods 17 3.1 Materials and material preparation . ............ 17 3.2 Test conditions . ....................... 17 3.3 Experimental set up ....................... 18 3.3.1 Electrochemical cell .................. 18 3.3.2 Tribocorrosion set up .................. 18 3.4 Experimental methods . .................. 19 3.4.1 Electrochemical tests.................. 19 3.4.2 Tribocorrosion tests . .................. 20 3.4.3 Fretting corrosion tests ................. 21 3.5 Surface analysis . ....................... 22 3.5.1 Microhardness . .................. 22 3.5.2 Optical microscopy . .................. 22 3.5.3 3D optical profilometry ................. 23 vii 4 Results and Discussion 25 4.1 Corrosion resistance of hafnium ................ 25 4.2 Tribocorrosion of hafnium . .................. 28 4.3 Fretting corrosion of hafnium .................. 30 5 Conclusions 35 6 Future Work 37 References 39 II Appended Papers 43 A Tribocorrosion of MoM implants 45 B Corrosion and Tribocorrosion of Hafnium 79 C Fretting Corrosion of Hafnium 97 Part I The Thesis 1 Chapter 1 Introduction In this chapter, the need for biomaterials is introduced. The most commonly used biomaterials are summarised, giving especial attention to the main groups of metals used for biomedical applications. Titanium and titanium alloys are discussed in more detail, and the possibilities of hafnium as an implant ma- terial are explored. Finally, the environment and conditions that biomaterials face when implanted into the body are discussed. 1.1 The need for biomaterials The human body is formed by a number of organs that work together as one unit. When one or more of these organs are damaged due to injuries, infections or different types of diseases, body function is affected. Different solutions have been developed to minimise the adverse effect of these injuries and dis- eases. Often, these solutions involve the implantation of biomedical devices in the patient’s body in order to replace or improve the function of human tissue. Biomaterials can be defined as materials used to make devices to replace a part or a function of the body in a safe, reliable, economic, and physiologically acceptable manner [1]. The implantation of biomaterials in the body implies different restrictions that must be considered to minimise the risk of failure and the need of revision of the implant (Figure 1.1). A biomedical device should not generate any adverse biological response after implantation. Therefore, biomaterials must be biocompatible, non toxic and non carcinogenic. Also, the possible degradation products generated during the lifetime of the implant must not lead to any adverse reactions. In addition, the physical and mechan- 3 4 CHAPTER 1. INTRODUCTION Figure 1.1: The main causes of implant failure that lead to revision surgery often combine biological aspects with material and engineering aspects. ical properties of the material must be adequate for the requirements of each particular application. The machining properties, the cost and the availability are also