Bingwen Lu

Self-healing conversion coating with gelatin–chitosan microcapsules containing inhibitor on AZ91D alloy

ABSTRACT The microstructure of cerium-based conversion coatings with and without microcapsules containing Ce(NO3)3 or La(NO3)3 on magnesium alloys were investigated and the corrosion resistance was evaluated as well. The gelatin–chitosan microcapsules were prepared by complex coacervation. Microcapsules can effectively avoid the traditional porous state, namely, by releasing active and repairing material immediately after changes in coating integrity. Microcapsules distribute in the tiny cracks of coating deposited on magnesium alloys. The electron probe micro-analyser results characterise the element distribution of coating. The potentiodynamic polarisation curve and impedance spectra show that the conversion coating with microcapsules can enhance the corrosion resistance of magnesium alloys. The microcapsules containing La(NO3)3 show a better corrosion resistance so as to promote a self-healing performance.

Effect of surface nanocrystallisation on the microstructure and wear resistance of vacuum carburised alloy

ABSTRACT In this work, a nanocrystallisation surface layer with an average grain size of 29 nm was fabricated on the 12Cr2Ni4A steel by the supersonic fine particles bombarding (SFPB). The vacuum carburising process was carried out on the original and the SFPB pre-treatment samples. X-ray diffraction, scanning electron microscopy and hardness tester were employed to study the phase constituents, grain size, hardness and residual stress of the two carburised samples. Experimental results showed that compared to the coarse-grain carburised layer (without SFPB), the carburised layer with SFPB pre-treatment has smaller martensite and carbide, and its thickness, hardness, compressive residual stress and wear resistance have been significantly improved. The dominant wear mechanisms of the two carburised samples were both abrasive wear and fatigue wear.