Protective compound coating on AZ91D Mg alloy fabricated by combination of cold spraying with die casting

Abstract

A novel processing that leads to the formation of a protective compound coating upon the AZ91D Mg alloy by the combination of cold spraying of Al–Mg alloy on a die cavity surface with subsequent die casting was discussed. The microstructure and phase composition of the coating were investigated using X-ray diffraction and scanning electron microscope coupled with energy dispersive spectroscopy. Results revealed that the coating consisted mainly of β phase (Mg₁₇Al₁₂) plus some Al and integrated with the substrate by mechanical interlocking and slender metallurgical bonding formed during the die casting process. A high bond strength of 82±5 MPa for the coating was achieved. The hardness and wear resistance of the AZ91D Mg alloy were greatly improved due to the compound coating. Simultaneously, the results of immersion tests and electrochemical corrosion tests indicated that the coated AZ91D Mg alloy specimens had better corrosion resistance compared with the bare AZ91D alloy specimen.

Keywords:

• Cold spraying
• Die casting
• Compound coating
• AZ91D Mg alloy
• Corrosion resistance

Acknowledgements

The authors gratefully acknowledge the National Natural Science Foundation of China (grant nos. 51001079, 51044007 and 51374151), the China Postdoctoral Science Foundation (grant no. 20100471586) and the Natural Science Foundation of Shanxi Province (grant nos. 2011011020-2 and 2010021023-1) for funding provided in support of this work.