Study On Oxidation Wear Mechanism Of Nickel-based Alloy Used In Rotary Calciners For Nuclear Waste Disposal

Under the constraints of the"dual-carbon"goal,vigorously developing nuclear energy is the inevitable choice to realize the transformation of our country’s energy structure.However,nuclear power plants generate large amounts of radioactive nuclear waste,which must be solidified before geological disposal.The latest technology for glass solidification of nuclear waste is the cold crucible induction furnace,which uses a rotary calciner system to transform high-level waste liquid.However,the operation life of rotary calciners is limited by the strong corrosive effects of the waste liquid on the scraping plate and structural materials at high temperatures,as well as the abrasion caused by calcining products on the furnace body.To address these issues,nickel-based superalloys can be used as a potential structural material for rotary calciners due to their high oxidation and abrasion resistance.Therefore,studying the oxidation wear of nickel-based superalloys under simulated rotary calcining furnace conditions is of great engineering significance and can help promote the development of Chinese glass curing technology.In this paper,a high temperature friction and wear tester MDW-02GF was designed specifically for the service environment of rotary calciners.The study focused on the high temperature oxidation and wear behaviors of three alloys,namely Inconel 625,Inconel 690and Hastelloy N.The testing was carried out at simulated rotary calciners at 600 and 800℃respectively.The weight loss method was used to compare the high temperature wear resistance of the alloys.The phase composition of the oxide film was analyzed using various techniques including scanning electron microscopy（SEM）,X-ray diffraction analysis（XRD）,and X-ray photoelectron spectroscopy（XPS）.Through these analyses,the high temperature oxidation wear mechanism was explored.The findings of the study are summarized as follows:（1）The study revealed that after subjecting the three alloys to high temperature oxidation wear at 600 and 800℃,Inconel 625 alloy demonstrated the least mass loss and exhibited excellent high temperature oxidation wear resistance.On the other hand,Hastelloy N alloy exhibited the most severe mass loss and the worst high temperature oxidation resistance.Moreover,as the temperature increased,the oxidation wear resistance of Inconel 625 alloy decreased,while the high temperature oxidation wear resistance of Inconel 690 and Hastelloy N alloys increased.（2）At 600℃,Inconel 625 alloy formed a continuous oxide film after rolling friction,which exhibited the best resistance to high temperature oxidation wear.The oxide film had three distinct layers,with the outermost layer being a loose Ni-Cr-O layer,the middle layer being a dense Ni-Cr-O layer,and the inner layer being a continuous dense Cr₂O₃ layer.In contrast,the oxide film formed by Inconel 690 alloy and Hastelloy N alloy was easily detached and removed under the action of friction.This led to a repeated process of oxidation and removal of the newly exposed alloy surface,resulting in an increasing weight loss of the alloy over time.（3）At 800℃,the oxidative wear of Inconel 625 alloy resulted in the formation of a continuous and compact inner layer of Cr₂O₃,which improved the binding force between the film layer and the substrate.The outer layer of the oxide film was composed of Ni O phase and Ni Cr₂O₄ phase,which enhanced the resistance of the alloy to oxidative wear.In contrast,the oxide film formed on Inconel 690 alloy was composed of Ni O phase and Ni Cr₂O₄ phase in the outer layer,and Cr₂O₃ in the inner layer.However,the oxide film tended to detach and fall off,leading to severe internal oxidation behavior and further aggravating the wear of the alloy.On the other hand,the oxidative wear of Hastelloy N alloy resulted in the formation of a single Mo-O layer,which constituted a loose and porous oxide film with a large number of cracks.The oxide film was prone to flaking off,exposing a new surface that was repeatedly worn off by oxidation.This led to the worst resistance to high temperature oxidative wear observed among the three alloys studied.