Research Of Metal-Based Namo-ceramic Coating Technology

Metal-ceramics grads material can alleviate the phenomenon of stress concentration in gradient composite layer,and exaltation integrated strength and anti-hot-shock ability on graded ceramic coating layer.Nano Al₂O₃ powder is main raw material,and Fe,Ni,Al powder are mixed to form compound metal alloy powder,according to different ratio of compound metal alloy powder,and passing to o lot of experiment,an optimization technology parameter was gained under the condition of pressureless sintering in Ar gas protection.Put forth effort to study the mechanical properties of FeNiAl/Al₂O₃ steps degree gradient composite layer,microstructure and wearing properties.The samples microstructure,phase constituent were investigated by SEM/EDS and XRD.We draw the conclusions as followed:FeNiAl/Al₂O₃ gradient composite layer presents a splinter shaped,fi'om the matrix to the surface of ceramics layer,along the thickness direction,the content of Al₂O₃ increased,while that of Fe-Ni-Al alloy decreased gradually,shows a gradient distribution of ingredient.The structure has a characteristic with macroscopically inhomogenous and microcosmic continuity.Additionally,a new phase FeAl₂O₄ was observed in the interface between gradient composite layer and 45# steel,which indicated there exists chemical reaction between the element in ceramic and Fe,at the same time,mutual diffusion between them.The micro-hardness,thermal shock resistance and abrasion resistance were respectively studied by numeral micro-sclerometer,circular calefaction and slippage abrasion.The capability variation rule of bonding layer was also analysed.It was indicated: The micro-hardness increased with the content of Al₂O₃ from substrate to surface along the direction of ceramic layer thickness,but declined in the A_l2O₃ ingredient section near Surface.The micro-hardness reached its maximum in the area contained 70%Al₂O₃.The thermal shock resistance of composite layer was preferable and was as three times as common ceramic coat.The addition of FeAlNi transition bottom and component gradient had some effect on improvement of thermal shock resistance.The failure mode of thermal shock behaved as shedding of ceramic layer.The intensity fell gradually with the times of thermal circulation.At last the damage mode behaved as slice shedding along the grain.The abrasion resistance of gradient composite layer was fine.The abrasion resistance of substrate 45# steel became 25 times as strong as former.It proved that gradient composite layer conduced to abrasion resistance.FeAlNi/Al₂O₃ gradient composite layer with specific component(about 40wt%FeAlNi) had better abrasion resistance than that of Al₂O₃ coating.FeAlNi/Al₂O₃ gradient composite layer presented different friction action under different load.The greater load,the higher abrasion rate it had and the worse abrasion resistance.The SEM of abrasion surface shows that the gradient variety along the direction of thickness of composite layer made the coat presented a friction abrasion mechanism, which behaved as grain shedding,crack emergence and crack spread,during the wearing process.