Study On Vacuum Metallurgy And Out-furnace Refining Process And Properties Of Ni-Al Alloy Rolling Ingots

In the modern industry,higher requirements are placed on engine emission standards and fuel economy with environmental concerns.Therefore,higher requirements are also placed on the spark plug in the engine combustion chamber,but it also causes spark plug oxidation corrosion and affects the service life.Therefore,it is necessary to develop a high-performance spark plug electrode material.In this paper,according to the performance requirements of the working environment of the spark plug,the vacuum metallurgy process is used to prepare NiAlSiY alloy materials.The alloy material is refined by electroslag remelting process to obtain NiAlSiY alloy with uniform and dense structure and high purity.The alloy is processed and tested by rolling and drawing processes to obtain high-performance electrode materials.Vacuum metallurgical process research shows that:Through analysis and comparison of different alloying powers,140 k W was selected as the most suitable.The alloy is mainly composed of Ni,Al Ni₃ and Al_0.9Ni_4.22 phases.The metallographic microstructure of the alloy consists of fine grains,larger columnar crystals,and central equiaxed crystals.There are many small holes and other defects on the surface of the alloy,mainly Fe O,Al₂O₃,Ca O,Ca O-Ca S.The hardness value of the alloy changes significantly,and the alloy composition is uneven.The electroslag remelting process study shows that:Through analysis of different melting currents,the remelting current of 2.8?3 k A was selected as the most suitable.The Y element in the electroslag ingot is almost completely burned,but the S and O elements are significantly reduced.The alloy phase has not changed.The metallographic microstructure shows that the grains become coarse,but there are no columnar crystals.The defects on the surface of the alloy basically disappeared,and the number and size of the inclusions were significantly reduced.The hardness value of the alloy does not change much,and the composition of the alloy is uniform.The prospect of electroslag remelting is discussed.By installing a protective cover around the consumable electrode on the mold and injecting Ar protective gas into the mold,the burning loss of Y element can be reduced,the desulfurization and deoxidation effect is more obvious and the inclusion in alloy can be further reduced during the electroslag remelting process.Rolling and drawing process research shows that the grains of the rolled sample and the drawn sample in the cross section will be elongated and relatively small,and the grain boundaries can be clearly seen.The plastic deformation of the structure of the profile is elongated,and the rolled samples can clearly see the grains and grain boundaries.The drawn grains change from polygonal to elongated,and the grain boundaries basically disappear.The hardness of the cross-section of the rolled sample is greater,and the hardness of the profile is smaller,and the hardness of the cross-section and the profile of the drawn sample is not much different.The tensile strength of the alloy wire is 520?550 MPa,and the elongation is about35%.The high temperature hot corrosion and high temperature oxidation test results show that:the corrosion kinetics curve of NiAlSiY alloy wire at 900?,20 h is close to the parabolic trend,the square curve of the weight gain ratio is close to a straight line,and the alloy wire has corrosion resistance at 900?.The main oxides of NiAlSiY alloy wire after corrosion are Al₂O₃ and Ni O,and the corrosion products are Al₂S₃.The oxidation kinetics of NiAlSiY alloy wire after oxidizing at 970?for 100 h basically conforms to the parabolic law,and the surface of the oxide film hardly falls off.It belongs to the anti-oxidation grade at 970?.After being oxidized at 970?for 100 h,the oxidation kinetics of 1090 alloy wire deviated from the parabolic law,and a large amount of oxide film fell off on the surface of the oxide film,which was a secondary anti-oxidation grade at 970?.The new nickel-based high-temperature alloy NiAlSiY has excellent high-temperature oxidation resistance,its high-temperature oxidation resistance is superior to the 1090 alloy,and can be used in a long-term environment at 970?.