Crack-Less Electrical Discharge Machining of Molybdenum with Titanium Electrode

Abstract:

This paper describescrack-less electrical discharge machining (EDM) of molybdenum (Mo) with titanium (Ti) electrode. Mo is often machined by EDM because of its high hardness. However, a molybdenum carbide (MoC and Mo₂C) layer with high hardness and brittleness is formed by EDM in kerosene oil. Moreover, Mo becomes recrystallizationembrittlement at high temperature. Therefore, many cracks occurred in the EDMed surface. On the other hand, the addition of Ti rises recrystallization temperature and improves high temperature strength of Mo.In order to decrease the cracks in the machined surface, Mo was machined by EDM with a Ti electrode in deionized water. In the case of the positive electrode polarity, many cracks occurred in the base material and recast layer. The cracks in the base material might generate by crystal grain boundary embrittlement. In contrast, the EDMed surface indicated crack-less on the negative electrode polarity. To clarify the causes of crack-less surface on negative electrode polarity, componential analysis of EDMed surface was carried out. The component ratio of Ti on the negative electrode polarity was higher than that on the positive. In addition, the recast layer was composed by Mo-Ti solid solution.

• Periodical: Applied Mechanics and Materials (Volume 510)
• Pages: 101-105
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.510.101
• Online since: February 2014
• Authors: Kaneko Kensei, Furutani Katsushi
• Keywords: Crack, Deionized Water, Electrical Discharge Machining (EDM), Molybdenum, Titanium

References

[1] H. Tsukahara, H. Minami, K. Masui, T. Sone: Formation of Carbide of Refractory Metals using Electrical Discharge Machining Process, Journal of the Japan Society of Electrical Machining Engineers, Vol. 39, No. 91 (2005), pp.16-23 (in Japanese).

DOI: 10.2526/jseme.39.91_16

[2] R. Demellayer, J. Richard: Precision Electro Discharge Machining of Molybdenum and Tungsten, Procedia CIRP, Vol. 6 (2013), pp.89-94.

DOI: 10.1016/j.procir.2013.03.030

[3] P. Allen, X. Chen: Process Simulation of Micro Electro-Discharge Machining on Molybdenum, Journal of Materials Processing Technology, Vol. 186 (2007), pp.346-355.

DOI: 10.1016/j.jmatprotec.2007.01.009

[4] J. Monaghan, D. Brazil, C. Sheridan: The Production of Cavities in Nickel Based Superalloys and Metal Matrix Composites using Electro-Discharge Machining, Key Engineering Material, Vols. 118-119 (1996), pp.85-92.

DOI: 10.4028/www.scientific.net/kem.118-119.85

[5] J. S. Moya, M. Diaz, C. F. Gutierrez-Gonzalez, L. A. Diaz, R. Torrecillas, J. F. Bartolome: Mullite-refractory metal (Mo, Nb) Composites, Journal of the European Ceramic Society, Vol. 28 (2008), pp.479-491.

DOI: 10.1016/j.jeurceramsoc.2007.03.020

[6] K. Kaneko, K. Furutani: Crack-less Electrical Discharge Machining of Molybdenum (1st Report) – Machining with Silicon Electrode -, Journal of the Japan Society for Precision Engineering (in press).

DOI: 10.2493/jjspe.80.197

[7] Y. Imai, C. Kawashima: Hand book of Heat Resistance Material, Asakura Publishing (1965), pp.236-241 (in Japanese).