Reinforced Pores in Porous Steels Obtained with Matrix Soluble Space Holders
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.388
Reinforced Pores in Porous Steels Obtained with Matrix Soluble Space Holders G.O. Neves1; G. Paz1; N. Araya1; C. Binder1; A.N. Klein1 1
Universidade Federal de Santa Catarina, Laboratório de Materiais, Campus Trindade, Florianópolis, SC 88040-900, Brazil.
ABSTRACT
This paper presents a novel way to obtain reinforced pores by the dissociation of mixed carbides during sintering. Porous materials have a wide range of applications such as dampeners, light structures, etc. But usually pores act as points of stress concentration and crack nucleation, harming the mechanical properties of these materials. Methods have been developed to control the shape and size of pores but, until now, there are no techniques that allow reinforcing the material around the pores. To address this, steels were prepared by adding 1, 3 and 5 wt.% of Mo 1.5Cr0.5C mixed carbide particles to a iron matrix by metal injection moulding. The results showed that during sintering, the dissociation of the carbide followed by the dissolution of the elements in the matrix generated rounded secondary pores with a reinforced vicinity, which increased the mechanical strength of the materials. The presence of rounded pores encircled by an enriched vicinity can allow the production of porous materials with exceptional fatigue strength and fracture toughness.
INTRODUCTION Porous materials are defined as such when their engineering function is made possible by the presence of pores in the volume of the material. They are heterogeneous materials formed by a 3D metallic or ceramic matrix forming the skeleton and pores that occupy, in most cases, between 20 and 97 % of the volume. Porous materials have several applications such as filters, materials for sound absorption, vibration control, light-weight structures, among others [1–3]. Several studies have noted that a porosity greater than 5 vol.% is exponentially detrimental to the material mechanical strength. Pores are volumetric discontinuities that can be treated as pre-nucleated cracks, which not only reduce the effective resistant area of the material but also act as stress concentrators. In addition, for dynamic loads, pores
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can facilitate both crack nucleation and propagation. Even a small crack propagation can result in large pores joining (pore-linking), which rapidly decreases the effective resistant area, resulting in premature fracture [4–7]. Powder metallurgy is a suitable technique to manufacture porous materials. Among other techniques, the use of space-holders is a known technique for controlling the total porosity, and the pore size, shape and distribution. This technique basically consists of the preparation of a biphasic composite consisting of a continuous matrix of metallic or cer
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