Damage mechanisms in silicon nitride wire rolling tools: lab-scale experiments and correlation with finite element modeling Iyas Khader a,b *, Andreas Kailer a a Fraunhofer Institute for Mechanics of Materials IWM, Freiburg, Germany b Institute for Reliability of Components and Systems IZBS, Karlsruhe Institute of Technology, Karlsruhe, Germany Abstract This study addresses the failure modes and damage mechanisms in silicon nitride rolling tools applied in caliber rolling steel wires. The study is based on experimental work conducted in conjunction with finite element simulations. Lubri- cated and unlubricated cold wire rolling experiments were conducted using two different grades of steel wires. The effects of lubrication and loading were taken into consideration when interpreting the outcomes. The correlation be- tween the experimental observations and numerical results enabled explaining damage nucleation and evolution in terms of stress fields. It was shown how the failure in silicon nitride rolls “switches” from fatigue induced damage to fast fracture, depending on the tensile stress fields. The importance of lubrication was emphasized by comparing surface and subsurface damage in both cases. Keywords Ceramics, silicon nitride, caliber rolling, wire rolling, rolling tools, damage 1 Introduction Early studies on silicon nitride, such as the work of Fukuhara et al. (1985), highlighted its exceptional properties such as high hardness, low thermal expansion, low density and superior performance in cutting tools. Additionally, high re- sistance against wear, corrosion and contact fatigue, combined with high temperature stability and low adhesion to metals, made silicon nitride a first choice ceramic for modern bearing applications (Katz and Hannoosh, 1985) and metalworking tools (Kailer and Hollstein, 2004). In the field of metalworking, tools made of silicon nitride and SiAlOns offer the potential of considerably enhanced service life and superior product quality. Examples of which are deep drawing (Kataoka et al. 2004), stamping and forging (Behrens et al. 2004) tools. Early work on ceramic rolling tools was conducted by Ohkohchi et al. (1992), who used SiAlON ceramics for cold rolling of thin steel sheets. Andersson et al. (2009) suggested that rolls made of ceramic composites exhibited a promising roll material candidate for hot rolling of steel bars. The authors experimentally showed that the wear of the ceramic composite was lower than that of a con- ventional reference cast iron material used in rolling tools. These considerations have encouraged researchers to test and apply silicon nitride as a material for rolling tools. Kailer et al. (2008) showed that silicon nitride rolls were successfully developed and tested for various industrial rolling applications, such as foil and sheet rolling. The mechanical strength of the ceramic rolls was proven to be sufficient for the high compressive stresses occurring in such applications. It was