CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 9555–9561 Strength of fine grained carbon-bonded alumina (Al 2 O 3 –C) materials obtained by means of the small punch test S. Soltysiak a,n , M. Abendroth a , M. Kuna a , Y. Klemm b , H. Biermann b a Institute of Mechanics and Fluid Dynamics, TU Bergakademie Freiberg, Lampadiusstraße 4, 09599 Freiberg, Germany b Institute of Materials Engineering, TU Bergakademie Freiberg, Gustav-Zeuner-Straße 5, 09599 Freiberg, Germany Received 15 January 2014; received in revised form 10 February 2014; accepted 10 February 2014 Available online 15 February 2014 Abstract Ceramic open cell foam filters are utilized for the reduction of non-metallic inclusions during casting of steel components. Fine grained carbon- bonded alumina (Al 2 O 3 –C) is used for the production of these porous filters. A new generation of Al 2 O 3 –C materials has been developed. The material has to withstand high mechanical loads during casting. Mechanical testing has to be applied to the material in order to ensure mechanical integrity of the filter structure. Standard sized specimens for the evaluation of the cold modulus of rupture (CMOR) are fabricated by uniaxial and isostatic pressing. The amount of binder (Cabores s P) is varied from 10 to 20 wt% in this study. The differences in the mechanical behavior between the various material compositions as well as differences between the different production routes are investigated by means of the small punch test. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Small punch test; Mechanical strength; Alumina; Carbon; Refractories 1. Introduction The fatigue life-time of steel components is mainly deter- mined by the presence of non-metallic inclusions [1,2]. Hence, ceramic filters are used for the reduction of non-metallic inclusions in cast components [3]. The material of the filters has to withstand the mechanical load applied by the weight and the inertia of the melt. A common procedure to evaluate the fitness for purpose of ceramic filters is the impingement test [4]. A systematic determination of material properties is not possible with this kind of test due to the arbitrary geometrical meso-structure of the filters. Standard tests are the three point bending test or a compression test for the evaluation of the cold modulus of rupture. These tests require a comparably large amount of material for each specimen. It was not possible to manufacture specimens for measuring CMOR in a reproducible manner using the slurry which is applied onto the filters [5]. A problem that occurred is the formation of large cracks inside the specimens during drying or coking. The chemical composition and the production route have therefore been changed to overcome this problem [6]. The influences of these changes on the mechanical properties of the material need to be characterized. A promising testing technique for fine grained ceramic materials is the small punch test (SPT). It has been used for the evaluation of material parameters of brittle materials [7,8]. The main advantage of the SPT is the small amount of material necessary for the test. The specimens have a thickness of t ¼ 500 μm and a diameter of d=8 mm. Thus, it is possible to produce specimens from the slurry used for the production of the filters. Moreover, the influence of size effects [9] can be minimized due to the fact that the specimen dimensions are close to the dimensions of the struts (d strut ¼ 400–500 μm) in a filter. The SPT enables one to perform many tests due to a short testing time. This is beneficial for the evaluation of statistically distributed material parameters. The slurry used for the production of the ceramic filters and the material used by Klemm et al. [6] are investigated by means of the small punch test. The latter material is tested in www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2014.02.030 0272-8842 & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Corresponding author. Tel.: þ49 3731 39 3371. E-mail address: stefan.soltysiak@imfd.tu-freiberg.de (S. Soltysiak).