Effect of Heat Treatment on Coated Ceramics for Composite Formation by Laser Processing

Sateesh N H, Mohankumar G C, Prasad Krishna

Abstract


Metal Matrix Composites (MMCs) now-a-days are gaining wide popularity because of their superior mechanical properties such as high mechanical strength; wear resistance, excellent thermal conductivity and ability to retain strength at high temperature. However, there still exist challenges in producing high quality MMCs by different laser additive manufacturing processes, and one such important process is Direct Metal Laser Sintering (DMLS). To obtain the highly densified products by DMLS the critical factor is attaining excellent bonding between the reinforcement and matrix. Further to achieve more improvement in uniform dispersion and mechanical properties, there is a need to focus on minimizing the interfacial reaction between the matrix and reinforcement. The above mentioned critical issues associated with MMCs are addressed in the recent times by improving the wettability of the reinforcement. Among these, metallic coating of the ceramic reinforcements are gaining wide spread acceptance to address the above issues. Electroless plating technique can be used to coat metallic coatings on ceramic reinforcements. Several parameters influence the process of coating, on the ceramic particles to get uniform and adherent deposition of metallic particles including pre-treatment of ceramic powder. With reference to the above facts, this paper focuses on the methodology for achieving a thin uniform Nickel-Phosphide (Ni-P) coating on Siliconcarbide (SiC) particles, which is the most commonly used ceramic reinforcement material to develop MMCs by DMLS process and also about the importance of heat treatment of ceramic powders after coating. Scanning Electron Micrograph (SEM), Energy Dispersive Spectroscopy (EDAX), and X-ray Diffraction (XRD) studies have been carried out on the coated ceramic particles. These studies clearly reveal the uniform coating of Nickel-Phosphide on ceramic particles and also reveal that the coating on the surface of the SiC is in amorphous before heat treatment and reaches crystalline state after heat treatment indicating the presence of stable Ni and Ni3P phases.


Keywords


Metal Matrix Composites (MMCs), Additive manufacturing (AM) process, Direct Metal Laser Sintering (DMLS), Electroless Plating, SiC, Heat treatment, Ni-P Coating, SEM, EDAX and XRD studies.

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