Effects Of Re And Y Elements On Interface Reactions Between Superalloy Melts And Ceramic Materials

In the casting process of single-crystal blades,the active elements in the alloy tend to react with ceramic material.It is led to superficial defects such as sand adhesions or pores on the surface of castings,which deteriorates the surface quality and mechanical properties of castings.The wettability between alloy melt and ceramic material affects directly the interfacial reactivity,and then affects the surface quality of castings.Therefore,the interface reactions and wettability are studied in this paper,the interface reaction laws and micromechanisms between superalloy melts and ceramic materials are studied systematically.And the influences of alloy composition,ceramic material composition and experimental atmosphere on the interface reactions and wettability are also discussed in depth.In this paper,a second generation nickel-base single-crystal superalloy is used as the based alloy.The effects of Re content on the interface reactions and wettability between superalloy melts and ceramic materials are studied by the method of sessile drop experiments.It is found that the wetting angle of the alloy/ceramic system increases when the content of Re in the alloy increases.The increase of Re content inhibits the interface reactions to some extent,and has a more obvious inhibition effect on the interface reactions between superalloy melt and ceramic mould.The effects of active element Y on interface reactions and wettability between superalloy melt and Al2O3-based ceramic mould are studied.The results show that Al and Hf in the alloy react with SiO2 in the ceramic mould when Y content is lower than 0.011 wt.%,and the reaction products are Al2O3 and HfO2.The adsorption of active element Y at the interface will increase the wettability of the system.When Y content is higher than 0.017 wt%,Y and Al in the alloy react with SiO2 in the ceramic mould.The main reaction product of 0.017 and 0.025 wt%Y alloys is Y3Al2(AlO4)3.The reaction products of 0.1 wt%Y alloy are Y3Al5O12 and Y4Al2O9,and the reaction products of 0.5 and 1.0 wt%Y alloys are Y2O3 and Y3Al5O12.The interface reaction process is that Y and Al react with SiO2 to form Y2O3 and Al2O3,respectively.Then Y2O3 combines with Al2O3 to form different yttrium aluminate oxides.The Si produced by the interface reactions will combine with[O]to form SiOx during the cooling.The wettability of the system increases significantly because of the interface reaction between Y and ceramic mould.The interface reactions and wetting behavior between SiO2-based ceramic core and Y-containing superalloy melt are studied in this paper,and the influence of experimental atmosphere on the interface reactions is also discussed.It is found that the active element Y is also an important factor affecting the interface reactions between alloy melt and ceramic core.Under vacuum condition,Al and Hf in the alloy react with the ceramic core when Y content is less than 0.011 wt.%,and the reaction products are Al2O3 and HfO2.When the content of Y exceeds 0.017 wt.%,Y in the alloy reacts with the ceramic core,and the interactions between Y and Al,Y and Ta occur.As the content of Y increases from 0.017 to 0.1 wt.%,Y,Hf and Al react with the ceramic core.The reaction products of 0.017 and 0.025 wt%Y alloys are Al2O3,Y3Al2(AlO4)3 and HfO2.The reaction products of 0.1 wt%Y alloy are YAlO3,Y3Al5O12,Y4Al2O9 and HfO2.However,Y,Ta and Hf participate in the interface reactions as the content of Y reaches 0.5 and 1.0 wt.%.The interface reaction products are Y2O3,TaC and HfC.Under Ar condition,Al reacts with the ceramic core to form Al2O3 for the alloys with Y content less than 0.017 wt.%.However,Y and Al react with the ceramic core for the alloys with Y content more than 0.017 wt.%.The reaction products of 0.017 and 0.1 wt%Y alloys are Y3Al2(AlO4)3 and Al2O3,while the reaction products of 0.5 wt%Y alloy are Y3Al5O12 and Y4Al2O9.Compared with the vacuum condition,the inert gas Ar reduces the interface reactions between alloy melt and ceramic core,and inhibits the interface reactions between ceramic core and Hf,Ta in the alloy.Under the two atmosphere conditions,the wetting angle of the system is greatly decreased due to the interface reaction between Y and ceramic core.The spreading kinetics of Y-containing superalloy melt on SiO2-based ceramic core and its controlling factors are studied using an improved sessile drop method.The results indicate that the spreading process of the alloy with different Y content on the ceramic core is the result of the combination of the adsorption of reaction elements at the interface and interface reaction.The adsorption of reaction elements plays a decisive role in spreading at the beginning of wetting,and the interface reaction plays a certain role in promoting spreading at the later stage.