Study On Preparation Of Plasma Sprayed Ni-based Coating And High Temperature Corrosion Resistance Of Biomass

In order to reduce greenhouse gas emissions,biomass fuels are gradually being widely used.However,the problem of high temperature corrosion in biomass burning boilers severely reduces boiler efficiency and service time.To delay the corrosion rate of biomass high temperature corrosion to the metal in the boiler,new coating spraying methods and new coating materials should be studied.Atmospheric plasma spraying technology can provide enough heat to completely melt any sprayed powder and form a relatively dense coating on the surface of the substrate.NiAl,as an aluminum-forming material,can effectively delay the corrosion rate of KCl in the existing research.Moreover,the corrosion resistance of the coating can also be effectively improved through the pre-oxidation treatment and the addition of corrosion-resistant elements.In addition,the research of boiler's environment,especially the effect of water vapor,is beneficial to the understanding of corrosion in the boiler.The specific research content is as followsNi+5wt.%Al coating and Ni-clad Al coating were prepared by atmospheric plasma spraying,and the coating was pre-oxidized at 700? for 6 hours.The orrosion resistance of coatings were compared under the same simulated biomass high-temperature corrosion environmen.The experimental results showed that the powder-mixed Ni+5wt.%Al will fall off during the spraying process and cannot be effectively deposited in the coating,resulting in poor corrosion resistance of the coating.The pre-oxidation treatment can form multiple layers of NiO on the surface and inside of the Ni+5wt.%Al coating,thereby delaying the corrosion rate.However,the method of Ni-clad Al can effectively protect the Al during the spraying process,and the corrosion resistance of the coating was relatively good.And through the pre-oxidation treatment,the coating not only formed multiple layers of NiO,but also formed NiAl phase around the Al-rich area,which further improved the corrosion resistanceThe Mo and Ni-clad Al powder were mixed by mechanical mixing,and Ni-clade Al+5wt.%Mo and 10wt.%Mo coatings were prepared by atmospheric plasma spraying.In the simulated biomass high temperature corrosion,the water vapor content and Mo element content were changed to study the effect on the corrosion rate.The experimental results show that under the condition of containing water vapor,the addition of Mo can effectively improve the corrosion resistance of the coating.In the absence of water vapor,the addition of Mo causes the cracking and peeling of the coating.The increase in water vapor content leaded to an increase in the oxygen partial pressure in the environment,which accelerated the formation and structure of oxides during the corrosion process,and to a certain extent,reduced the stress concentration between oxides.The increase in the content of Mo can improve the structure of oxide formation and reduce the formation of chlorides in the coating.However,to a certain extent,stress concentration may be formed,causing the coating to peel off.