Effect of Heat Treatment Temperature on the Coating Microstructure and Properties of Thin Al-Si Coated Hot Formed Steel

For investigating the optimal surface properties of thin aluminum-silicon coated steel plate after hot forming，the Al-10Si thin coated hot formed steel plate was taken as the research object， and the effects of different heat treatment temperatures on the microstructure and properties of the steel plate were studied by means of scanning electron microscopy， glow discharge emission spectrometer， micro-Vickers hardness tester， laser confocal microscope and friction and wear testing machine.Results showed that when the heat treatment temperature increased from 820 ℃to 930 ℃， the mutual diffusion of Al， Fe and Si progressively intensified.From the perspective of microstructure， the Fe-Al-Si phase in the coating，the diffusion layer between the coating and the steel substrate and the total thickness of the coating gradually increased，the martensite content in the substrate increased，and the shape showed a tendency of coarsening.From the element distribution，the diffusion extent of Al， Si and Fe in the coating increased，and the element concentration gradient became gentle gradually.From the property of coating，the hardness of coating increased first and then decreased.Moreover， the friction coefficient increased first and then decreased， and the curve fluctuation of friction coefficient increased.The end wear of the scratch decreased obviously at first and then increased slightly，and the bottom undulation of the furrow touched by the pointer gradually increased.