Effects Of Alloy Elements On Interfacial Reaction Of Ni-Based Superalloy And Ceramic Materials

In investment casting of superalloys,interface reactions between the molten alloy and the ceramic mould would cause superficial defects on the casts,such as sand adhesions or reaction layers.The sand adhesions and reaction layers would reduce the surface quality and affect the subsequent machining of the casts.The main factors that affect the wettability include the active element in the alloy,the active component in the ceramic,atmosphere as well as the casting temperature.Accordingly,it is of great importance to investigate the interface reactions between the molten superalloy and the ceramic material.The influence of the active elements in the alloy and the active component in the ceramic on the interface reactions was studied carefully and the research findings have both great theoretical and practical significance.Interface reactions were investigated by the method of sessile drop experiment.The effects of active elements on the interfacial reaction between superalloy and high-purity Al2O3 ceramic materials were studied by changing the contents of active elements C,Cr and Hf in the alloy.The morphologies of the interfacial reaction products were observed by SEM and the phases of the products were analyzed by XRD and XPS.The results shows that the interfacial reaction between C and Al2O3 ceramic material was happened,and the Al2O3 ceramic particles are infiltrated into the alloy matrix,the penetration depth was about 40?m.There was no chemical reaction between Cr and Al2O3 ceramics.When 0.2 wt.%C element is added,the interfacial reaction occurs to form 9Al2O3-Cr2O3.Hf and Al2O3 reacted to form HfO2 flake.After adding 0.2 wt.%C,the C element was involved in the interfacial reaction,formed Al2O,Al and CO gas,destroyed the HfO2 flake.The interfacial reaction of actively elements C,Cr,Al and Hf with SiO2 in the alloy was studied by using the sessile drop test.It was found that the interfacial reaction between Cr and SiO2 resulted in the formation of adhering sand,the main components were SiO2 and Cr2O3,and the thickness was about 30 ?m,When 0.2wt.%C element is added,at the bottom of adhering sand,there are some holes generated,and adhering sand became heavier.Al with SiO2 has interfacial reaction to form more stably Al2O3 at the reaction interface.Hf element with SiO2 has an interfacial reaction to form HfO2 layer.The interfacial reaction of actively elements C,Cr,Al and Hf with ZrSiO4 was studied by using the sessile drop test.It was found that the interfacial reaction between the Ni-0.45C alloy and ZrSiO4 ceramic material,discovered the the bottom of the alloy mainly remains Zr oxide.Ni-9Cr alloy reacts with SiO2,a decomposition product of ZrSiO4,and generates Cr2O3 at the bottom of the alloy.The interface reaction between Ni-3Hf and ZrSiO4 ceramic material occurs at high temperature to form HfO2,After the addition of Al,the area of the interfacial reaction product relatively reduced.