Investigation on the Electrical Properties of Vacuum Cold Sprayed SiC-MoSi 2 Coatings at Elevated Temperatures

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JTTEE5 20:892–897 DOI: 10.1007/s11666-011-9635-z 1059-9630/$19.00  ASM International

Investigation on the Electrical Properties of Vacuum Cold Sprayed SiC-MoSi2 Coatings at Elevated Temperatures Y.-Y. Wang, Y. Liu, C.-J. Li, G.-J. Yang, J.-J. Feng, and K. Kusumoto (Submitted December 10, 2010; in revised form February 6, 2011) SiC-MoSi2 composite powders was prepared by wet milling with MoSi2 powders and SiC loose grinding ball in alcohol solution. Vacuum cold spray (VCS) process was used to deposit SiC-MoSi2 electric conducting composite coatings. The microstructure of the VCS SiC-MoSi2 composite coatings were characterized by scanning electron microscopy. The electrical resistance of the coatings was measured using a four-point probe method. The effects of the deposition parameters on the electrical resistivity of the composite coatings were investigated. The electrical properties of the coatings at elevated temperatures in air and Ar gas atmospheres were also explored. The results show that the electrical resistivity of SiC-MoSi2 coatings decreases with increasing He gas flow rates ranged from 3 to 6 L/min. The electrical resistivity increases with the increase in heat treatment temperature due to ‘‘pesting’’ behavior of MoSi2. The electric conductive property of the VCS SiC-MoSi2 coating is significantly improved after heat treatment at 1000 °C for 3 h in Ar protective atmosphere without oxidation. A minimum resistivity of the heat treated coating is 0.16 X Æ cm.

Keywords

electrical properties, SiC-MoSi2 composite coating, vacuum cold spray oxidation

1. Introduction Vacuum cold spray (VCS) is a novel spray technology that enables deposition of ceramics on various substrates such as metals, ceramics, and plastics. The method is based on shock-loading solidification. In the process, ultrafine ceramic particles are accelerated up to a very high velocity by carrier gas through a micro-orifice nozzle and subsequently impact and form a coating on a substrate in a chamber under vacuum conditions at room temperature. Because the solid ceramic powder is mixed with a carrier gas to form an aerosol flow, the technique is also called aerosol deposition (AD) method (Ref 1). VCS has received much attention because of its outstanding advantages: (a) at the low deposition temperature (room temperature), the microstructure of the feedstock can be transferred into the as-deposited coating without any crystal grain growth or structural changes and (b) the high deposition efficiency (ranging from several lm/min to several tens of lm/min) (Ref 1, 2).

Y.-Y. Wang, Y. Liu, C.-J. Li, G.-J. Yang, and J.-J. Feng, State Key Laboratory for Mechanical Behavior of Materials, Xian Jiaotong University, Shaanxi 710049, China; and K. Kusumoto, Department of Mechanical Systems Engineering, Engineering Faculty of Gunma University, Gunma 376-0052, Japan. Contact e-mail: [email protected].

892—Volume 20(4) June 2011

Silicon carbide (SiC) demonstrates excellent thermal properties (such as high thermal conductivity, structural stability

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