Surface characteristics and erosion phenomena in WEDM of alumina composites

ABSTRACT

Reinforcing the ceramic materials with a conducting filler allows the net electrical properties to increase. This makes the composites machinable by electrical discharge process. Present work identifies the influence of multi-walled carbon nanotubes (MWCNT) as conducting fillers toward the machined surface profile. Alumina composites with 5 and 10 vol. % MWCNTs are fabricated and machined by wire electrical discharge machining process. The spalling effect is found to be more dominant at lower MWCNT concentrations in the composites. Cracks, porosity, and oxidization of the surface materials are the main defects observed during the machining process. Also, a more intense cracks and porous behavior is observed at lower concentration of MWCNT (5 vol. %). A closer analysis of machined surface edges yielded some phenomena of mechanical erosion and chipping due to physical contact. This situation is brought forward by low electrical conductivity and high brittleness of the composites. The Energy Dispersive X-Ray (EDX) analysis confers toward actual dissociation and melting of the carbon nanotubes even at low concentration of MWCNTs (5 vol. %) though not readily visible.

KEYWORDS:

• Alumina
• MWCNT
• erosion
• WEDM
• porosity
• cracks
• subsurface
• spalling

Acknowledgments

The authors are grateful to Dr. Devasish Chowdhury, IASST Guwahati, India, for the FESEM facility.

Additional information

Funding

The Slovak Research and Development Agency has supported this work (project no. APVV- 15-0469, Ceramic materials for extreme operating conditions) and project CERANEA (Multifunctional Ceramic/Graphene Coatings for New Emerging Applications).