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MoB/CoCr Cermet Coatings by HVOF Spraying against Erosion by Molten Al-Zn Alloy

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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 dipping 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 dipping 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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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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Authors and Affiliations

  1. Thermal Spray Materials Department, Fujimi Incorporated, Kakamigahara, Gifu Pref., 509-0103, Japan

    Hiroaki Mizuno & Junya Kitamura

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  1. Hiroaki Mizuno
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  2. Junya Kitamura
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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

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