Effects of Ni and TiN Coatings on the Alumina/Heat-Resistant Steel Interface Properties
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Springer 2006
Effects of Ni and TiN Coatings on the Alumina/ Heat-Resistant Steel Interface Properties ENZE WANG, YONG YI, HUA XIE and YONGGE FAN School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621002, PR China. e-mail: [email protected] (Received 27 January 2005; accepted 10 October 2005) Abstract. Ni and TiN coatings on alumina particles were achieved using a chemical vapor deposition (CVD) method. The coated alumina was then used as raw materials to prepare alumina/ heat-resistant steel (HRS) composites. The effects of Ni/TiN coatings on the alumina/HRS interface strength and oxidation resistance at elevated temperature were investigated. It is found that the both coatings can improve the alumina/HRS interface bonding strength and Ni coating has a more significant effect. For the composite made from Ni-coated alumina and HRS, the interface exhibited a better oxidation resistance due to the dissolution of Ni coating into the HRS matrix. However, the composite of TiN-coated alumina/HRS has a poor oxidation resistance behavior because TiN still existed on the alumina/HRS interface. Key words: coatings, composites, interface properties.
1. Introduction There is not any ideal material suitable to sustain for long lifetime under the conditions of high temperature oxidation and abrasive wear, although this working environment is very popular in many industrial areas. The alumina reinforced HRS composite may be a good candidate for service under such severe conditions because alumina particles possess good thermal stability, high hardness and good wear resistance. In addition, the HRS matrix has fine oxidation resistance and high strength at elevated temperature. However, the composite macro-properties mainly depend on their interfacial properties. If the alumina/HRS bonding strength is low, or the oxidation resistance of the interface is not good, hard alumina particles will be pulled out of the matrix and then they cannot be considered as a promising wear resistant material, so the improvement of composites properties relies essentially on reinforcement of their interface. There are many methods to improve ceramic particle/metal matrix composite interface. Among those, the most efficient way is to form a coating on the hard ceramic particles. So that the interface compositions can be controlled and the materials properties can be improved.
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Figure 1. Fabrication of the sample.
The primary aim of using Ni or TiN coating alumina particles for alumina/ HRS composite is to improve the wettability between alumina and HRS matrix. Then the alumina/HRS surface-layer composite can be made using an infiltration casting method [1, 2]. After the introduction of Ni/TiN coatings into the composite, questions arise for its influence on microstructure and bonding strength of the alumina/HRS interface. The objectives of this paper are to examine these concerns. 2. Effects of the Coatings on the Interface Bonding Strength 2.1. EXPERIMENTAL CON
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