Abstract
MoB/CoCr, a novel cermet material for thermal spraying, with high durability in molten alloys has been developed to utilize for aluminum die-casting parts, and for hot continuous dip** rolls in Zn and Al-Zn plating lines. The durability of the MoB/CoCr coatings prepared by high velocity oxy-fuel (HVOF) spraying has been investigated using a molten-metal immersion tester. The tests revealed that the MoB/CoCr coating has much higher durability without dissolution in the molten Al-45wt.%Zn alloy. Little change of crystal structure, mainly composed of double borides of CoMoB and CoMo2B2, is observed after the immersion test, suggesting that the double borides have much higher durability. Using undercoat is effective to reduce the influence of large difference in thermal expansion between the MoB/CoCr topcoat and substrate of stainless steel of AISI 316L, widely used for the hot continuous dip** rolls. Optimized thickness combinations of topcoat and undercoat are necessary to obtain intrinsic performance of low reactive MoB/CoCr against the molten Al-45wt.%Zn alloy.
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References
J.R. Davis, Ed., Handbook of Thermal Spray Technology, ASM International, 2004, p 56-60, 62-70, 133-168
R.B. Heimann, Plasma-Spray Coating, Principles and Applications, VCH Verlagsgesellschaft mbH, Germany, 1996
K. Hamashima, Y. Shinozaki, and M. Sasaki, Thermal Spraying of Mo2NiB2-Ni Cermet, Proc. International Conference on Powder Metallurgy & Particulate Materials, Advances in Powder Metallurgy & Particulate Materials, part2, (Chicago, USA), Metal Powder Industries Federation and APMI International, 1997, p 43-48
H. Yamaguchi, T. Hisamatsu, Reaction Mechanism of the Sheet Galvanizing, J. Iron Steel Inst. Japan, 63(7), 1977, p 1160-1169 (in Japanese)
T. Tomita, Y. Takatani, Y. Kobayashi, Y. Harada, H. Nakahira, Durability of WC/Co Sprayed Coatings in Molten Pure Zinc, J. Iron Steel Inst. Japan Int. 33(9), 1993, p 982-988
K. Tani, T. Tomita, Y. Kobayashi, Y. Takatani, Y. Harada, Durability of Sprayed WC/Co Coatings in Al-added Zinc Bath. J. Iron Steel Inst. Japan Int. 34(10), 1994, 822-828
A.J. Stavros, Behavior of Some Tungsten Carbide Coatings in Molten Zinc, Proc. of 9th National Thermal Spray Conference, C.C. Berndt, Ed., Oct 7-11 (Cincinnati, OH), ASM International, 1996, p 141-146
D. Nolan, P. Mercer, and M. Samandi, Reactivity of WC-12% Co Thermal Spray Powders with Molten Zinc Alloys as a Function of Phase Content, Surface Modification Technologies XI, T.S. Sudarshan, M. Jeandin, and K.A. Khor, Eds., The Institute of Materials, 1998, p 312-317
H. Mizuno, J. Kitamura, S. Osawa, and T. Itsukaichi, Development of Durable Spray Coatings in Molten Aluminum Alloy, Proc. International Thermal Spray Conference 2005 (Basel, Switzerland), ASM International, 2005, CD-ROM
H. Mizuno, J. Kitamura, S. Tawada, and T. Itsukaichi, Development of Durable Spray Coating in Molten Al and Al-Zn alloys, Proc. 1st Asian Thermal Spray Conference (Nagoya, Japan), Asian Thermal Spray Committee, 2005, p 81-82
H. Mizuno, J. Kitamura, S. Tawada, and T. Itsukaichi, MoB/CoCr Spray Coating with Higher Durability in Molten Al and Al-Zn Alloys, Proc. International Thermal Spray Conference 2006 (Seattle, USA), ASM International, 2006, CD-ROM
K. Hamashima and Y. Shinozaki, Development of the Thermal Spraying of Mo-Ni-B Cermet I: Preparation of Spraying Powder and Properties of its Films, Pre-Prints of the National Meeting of Japan Welding Society, Japan Welding Society, Vol. 62, 1998, p 154-155
K. Hamashima and Y. Shinozaki, Development of the Thermal Spraying of Mo-Ni-B Cermet II: Effects of the Heat Treatment on Properties of its Films, Pre-Prints of the National Meeting of Japan Welding Society, Japan Welding Society, Vol. 63, 1998, p 72-73
T. Itsukaichi and S. Osawa, US Patent 6984255
Acknowledgment
The authors thank Mr. Isao Aoki, Mr. Satoshi Tawada, and Mr. Yoshiaki Hayashi for their technical support. The authors also thank Mr. Nobuaki Kato for his valuable suggestion.
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Mizuno, H., Kitamura, J. MoB/CoCr Cermet Coatings by HVOF Spraying against Erosion by Molten Al-Zn Alloy. J Therm Spray Tech 16, 404–413 (2007). https://doi.org/10.1007/s11666-007-9046-3
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DOI: https://doi.org/10.1007/s11666-007-9046-3