Journal of Mechanical Science and Technology 33 (5) (2019) 2085~2091 www.springerlink.com/content/1738-494x(Print)/1976-3824(Online) DOI 10.1007/s12206-019-0412-0 Enhancement of metal creep lifetime by graphene coating † Fahim Ahmed Ibupoto 1 , Jang Gyun Lim 2 , Dongmok Lee 3 , Seunghyun Baik 1 and Moon Ki Kim 1,2,* 1 School of Mechanical Engineering, Sungkyunkwan University, Suwon 16419, Korea 2 Sungkyunkwan Advanced Institute of Nano Technology (SAINT), Sungkyunkwan University, Suwon 16419, Korea 3 Institute of Advanced Machinery and Technology, Sungkyunkwan University, Suwon 16419, Korea (Manuscript Received May 19, 2018; Revised December 4, 2018; Accepted January 12, 2019) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract An advancement can be seen in ultra-thin coatings used for the enhancement of material durability and lifespan. Among candidate ma- terials, copper is used in various applications, such as micro sensors, nuclear fuel waste deposition canisters, and International Thermo- nuclear Experimental Reactor first walls. However, it is easily susceptible to metal creep, due to its exposure to harsh environments. In this study, graphene, a promising ultra-thin material, is tested as a single-layer coating substance used to enhance the creep property of copper. For measuring creep life, the small punch creep test methodology is adopted. Results show that, remarkably, the creep lifetime of copper increases by up to 19 % with the use of the graphene coating. In testing, the heat-treated copper specimen without graphene was fractured at 45 hours, while the graphene-coated copper specimen was fractured at 55.4 hours. The finite element method also supports the experimental results obtained. Keywords: Creep rupture; Finite elemental method (FEM); Heat-treated copper (HT-Cu); Single-layered graphene copper (SG-Cu); Small punch creep test (SPCT) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction In recent times, a rapid advancement has occurred with re- spect to ultrathin coatings research for preserving/increasing substrate materials’ integrity. Study has mostly focused on enhancing the corrosion resistance at various temperatures and under different conditions [1, 2]. In our work, however, we focused on enhancing the mechanical properties by coatings. In this regard, single-layer graphene, having a thickness of 0.355 nm [3], represents a very attractive and promising mate- rial, as it demonstrates extremely unique properties. Up until the last several years, it had mostly been studied and em- ployed for its high electrical, optical, and super lubricity prop- erties [4-8], with a relatively fewer efforts focused on its me- chanical properties—although, it is known that it has excellent mechanical properties, such as a Young’s modulus of 1 TPa [3]. In order to improve the mechanical properties by gra- phene coating, the adhesion between the material being coated and the graphene should be excellent. Copper is one such material that is being used in various industries [9-11]. One of the applications of copper is in the real-time moni- toring of the manufacturing systems of metal tooling struc- tures for reducing response times, lowering operating costs, and improving product output and quality [9]. Manufacturing systems operating at high temperatures and pressure levels and with severe strain have a high compulsion of in-situ tem- perature, pressure, and strain monitoring at critical areas [12]. Due to their small-scale size, micro sensors can be potentially be placed into systems without conflicting with the normal operation of the system. As these thermal/mechanical sensors are placed in harsh conditions, consequently, it is essential to consider their creep lifetime [13]. Due to continuous exposure to high temperatures and stress, the sensor workpieces can creep rupture and damage the sensors themselves. In light of this, we believe that, by adding the graphene coating presented in this paper, the creep lifetime of micro sensor copper work- pieces can be significantly increased. Another application in the coming years for the graphene coating discussed herein would also be in nuclear fuel waste deposition canisters and over the years, interest has grown regarding the use of copper as a nuclear fuel waste canister material for long-duration storage [14]. Ideally, these canisters should retain their integrity for thousands of years in the face of corrosion and internal and external stresses [15]. However, in some cases, constant internal and external stress causes the copper to develop creep deformation and cracks, eventually leading to rupture of the canister [16]. Furthermore, the ap- pearance of corrosion in conjunction with creep strain can expedite this rupture time period. Therefore, our research * Corresponding author. Tel.: +82 31 299 4840 E-mail address: mkkim@me.skku.ac.kr † Recommended by Associate Editor Sung-Hee Yoon © KSME & Springer 2019