Study On Structure Regulative Mechanism Of The [(Cr_1-x,Al_x)₂O₃+Cr] Eutectic Nanocomposition Coating Perpared By Reactive Plasma Spraying

In this paper,based on the thermite reaction:2Al+Cr₂O₃=2Cr+Al₂O₃,and composite feedstocks were fabricated successfully with Al2O3 and Cr2O3 used as additives.The metal and ceramic eutectic composite coating can be obtained with part nano-phase structure by reactive plasma spraying.The phase composite microstructure,wear resistance and high-temperature behavior were investigated.The main phases of composite coating were?Al,Cr?2O3 solid solution,which consisted of Cr₂O₃,Al₂O₃ and Cr.The microstructure of the composite coatings can be regulated by changing the composition of the additives.Experimental results show that for getting 100%of the eutectic organization,the additive mast be added to the composite powder.The effect of compound additives?Cr₂O₃+Al₂O₃?on the eutectic coating is better than that of single Cr2O3.The amount of additives are determined by the proportion of additives of Al2O3 and Cr2O3.The amount of metal of the eutectic organization is higher than that of ceramic when the additives are small scale in within certain limits.The change of the proportion and addition of additives not only can change the proportion of metal and ceramic phase in the eutectic coating,but also the phase composite of ceramic solid solution.The regulation of coating is determined by the change of the proportion of additives and adding quantity.But coating can't be controlled by adding single Al₂O₃ additives.The microhardness of eutectic composite coating is 1899HV,which is higher than that hypereutectic composite coating and hypoeutectic composite coating.Eutectic composite coating with smooth wear surface,less peeling off area,and namametal particles?10-20nm?are dispersed in the?Al,Cr?2O3 ceramics substrate,which can control the crack initiation,put off the crack expanding and improve[Cr+?Al,Cr?2O3]eutectic coating toughness and wear resistance significantly.The wear mechanism of eutectic composite coating is fatigue wear and mild adhesive wear.The eutectic composite coating has high-temperature oxidation resistence,because it is compact and metal Cr particles distribute dispersedly in the?Al,Cr?2O3 ceramics substrate,oxygen entering to the internal coating is difficult,which resisted oxygen diffusing into the coating.The high-temperature oxidation resistance of eutectic composite coating is perfect under the 800?,although the performance is decreased a little under the 1000?it's still favorable.The eutectic composite coating has compact organization,in addition,crack that produced in the process of thermal shock is blocked by the tiny and dispersion Cr particle,so the eutectic composite coating has good thermal shock performance.The number of thermal shock is 95 times.