Availableonlineatwww.sciencedirect.com WEAR ELSEVIER wear260(2006)634-641 www.elsevicr.com/locatewear Tribological behaviour of SinA and Si3N4-ooTiN based composites and multi-layer laminates M. Hadad a,*G. Blugan.J Kubler D.E. Rosset. L Rohr a J Michler a erkerstr: 39. CH-3600 Thun Swit b EMPA, Laboratory for High Performance Ceramics, 8600 Duebendorf, Switzerland Received 12 January 2004; received in revised form I March 2005: accepted 16 March 2005 Available online 24 June 2005 Abstract Si3N4-Tin based multi-layer laminates exhibit differences in residual stress between individual layers due to a variation of the thermal expansion coefficient between the layers. The residual stress distribution in these multi-layer laminates is known to improve the apparent macroscopic fracture toughness. In this work, the tribological behaviour of bulk, composites and multi-layers laminates are investigated. Si3N4 bulk, Si,Na based composites with 10, 20 and 30 wt% Tin and different multi-layer laminates have been tested under dry conditions with reciprocal movement using a ball-on-block configuration In particular, the infuence of sliding directions with respect to the layer orientations has been investigated The experimental results show that wear resistance increased with increasing tiN content in Si3N4-TIN composites. However, multi-layer laminates exhibit an up to three times higher apparent fracture toughness, but do not show an improvement of wear resistance compared to C 2005 Elsevier B V. All rights reserved Keywords: Silicon nitride; Composites and laminate ceramics; Ball-on-block wear testing; Anisotropy; Wear mechanism Introduction toughness up to 100% and to enhance fracture strength up to 1000 MPa [ 8]. This has been attributed mainly to resid Silicon nitride Si3 N4 based ceramics have attractive phys- ual stress at hetero-phase boundaries(Si3 N4-TIN) caused by ical properties such as high hardness, chemical inertness and mismatch of thermal expansion coefficient between TIN and low density. One of the most important applications are cut- Si3 N4. Similarly, multi-layer ceramic laminates have been ting tools and machining of hard materials, like cast iron and previously reported to have considerable improvement in nickel based alloys [1, 2]. The main limitations of ceramic macroscopic fracture toughness [11-13]. This was attributed cutting tools are their low tensile strength and fracture tough- to crack deflection due to the presence of residual stresses ness. Different approaches to improve mechanical properties between the layers. Si3N4 based laminates have therefore like fracture toughness and wear performance include:(a) the potential for considerable improvements in term of prod enforcement by a textured second phase or multi-layer uct lifetime and energy consumption reduction for several laminates [3-5] and composites and(b)second phase addi- applications, e.g. cutting tools [14]. Similar to composites, tions such as Tin or TiB2 being dispersed homogenously additional residual stresses are formed within laminates due into the matrix of Si3N4 [6-10]. Silicon nitride compos- to the difference in thermal expansion coefficient between ites with 230-40 wt% TiN have shown to increase fracture two layers(Si3 N4 and Si3N4-TIN composite)upon cooling from the sintering temperature Corresponding author. Tel: +41 33 228 2963; fax: +41 33 228 44 90. The abrasive wear resistance of materials has been E-mail address: mousab. hadad @empa.ch(M. Hadad) reported to increase generally with both increasing hardness 0043-1648/- see front matter O 2005 Elsevier B V. All rights reserved doi:10.1016/wear2005.03.027Wear 260 (2006) 634–641 Tribological behaviour of Si3N4 and Si3N4–%TiN based composites and multi-layer laminates M. Hadad a,∗, G. Blugan b, J. Kubler ¨ b, E. Rosset c, L. Rohr a, J. Michler a a EMPA, Swiss Institute for Material Science and Technology, Feuerwerkerstr. 39, CH-3600 Thun, Switzerland b EMPA, Laboratory for High Performance Ceramics, 8600 Duebendorf, Switzerland c University of Applied Sciences of Geneva, Switzerland Received 12 January 2004; received in revised form 1 March 2005; accepted 16 March 2005 Available online 24 June 2005 Abstract Si3N4–TiN based multi-layer laminates exhibit differences in residual stress between individual layers due to a variation of the thermal expansion coefficient between the layers. The residual stress distribution in these multi-layer laminates is known to improve the apparent macroscopic fracture toughness. In this work, the tribological behaviour of bulk, composites and multi-layers laminates are investigated. Si3N4 bulk, Si3N4 based composites with 10, 20 and 30 wt% TiN and different multi-layer laminates have been tested under dry conditions with reciprocal movement using a ball-on-block configuration. In particular, the influence of sliding directions with respect to the layer orientations has been investigated. The experimental results show that wear resistance increased with increasing TiN content in Si3N4–TiN composites. However, multi-layer laminates exhibit an up to three times higher apparent fracture toughness, but do not show an improvement of wear resistance compared to composites. © 2005 Elsevier B.V. All rights reserved. Keywords: Silicon nitride; Composites and laminate ceramics; Ball-on-block wear testing; Anisotropy; Wear mechanism 1. Introduction Silicon nitride Si3N4 based ceramics have attractive phys￾ical properties such as high hardness, chemical inertness and low density. One of the most important applications are cut￾ting tools and machining of hard materials, like cast iron and nickel based alloys [1,2]. The main limitations of ceramic cutting tools are their low tensile strength and fracture tough￾ness. Different approaches to improve mechanical properties like fracture toughness and wear performance include: (a) reinforcement by a textured second phase or multi-layer laminates [3–5] and composites and (b) second phase addi￾tions such as TiN or TiB2 being dispersed homogenously into the matrix of Si3N4 [6–10]. Silicon nitride compos￾ites with 230–40 wt% TiN have shown to increase fracture ∗ Corresponding author. Tel.: +41 33 228 29 63; fax: +41 33 228 44 90. E-mail address: mousab.hadad@empa.ch (M. Hadad). toughness up to 100% and to enhance fracture strength up to 1000 MPa [8]. This has been attributed mainly to resid￾ual stress at hetero-phase boundaries (Si3N4–TiN) caused by mismatch of thermal expansion coefficient between TiN and Si3N4. Similarly, multi-layer ceramic laminates have been previously reported to have considerable improvement in macroscopic fracture toughness [11–13]. This was attributed to crack deflection due to the presence of residual stresses between the layers. Si3N4 based laminates have therefore the potential for considerable improvements in term of prod￾uct lifetime and energy consumption reduction for several applications, e.g. cutting tools [14]. Similar to composites, additional residual stresses are formed within laminates due to the difference in thermal expansion coefficient between two layers (Si3N4 and Si3N4–TiN composite) upon cooling from the sintering temperature. The abrasive wear resistance of materials has been reported to increase generally with both increasing hardness 0043-1648/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2005.03.027