| GH4169 is a Ni-based deformed superalloy that is imitation of the American Inconel 718 alloy and developed independently in China.The structure of the alloy is mainly composed of γ matrix,γ′,γ″ phase and carbide.Because of its excellent performance at high temperature The mechanical and creep properties,good thermal process and welding performance have been widely used in various fields such as aviation,aerospace,petroleum,chemical and energy.The content of Ni and Cr in early high-temperature alloys was 4:1,and nickel was initially developed The method of base deformation superalloy is to adjust the production by adding a small amount of Al and Ti to improve the creep strength and oxidation resistance of the alloy at high temperature,so as to achieve the use temperature of the alloy can be roughly divided into two categories:Ni.Cr-Al.Ti.W-Mo.Ta series and Ni.Cr-Al series alloys.Nickel base deformed superalloy GH4169 is widely used due to its good corrosion resistance and oxidation resistance under high temperature and high stress conditions In life,scientific research and other fields.This article uses two different heat treatment methods to study the effect of pre-deformation heat treatment on the creep properties of GH4169.Under the same temperature and different stress conditions,the creep fracture mechanism of GH4169 alloy was analyzed.The heat treatment methods are mainly in the following two categories: one is after solution treatment,cold drawing deformation 9.8%,14%,20%,annealing at 930°C for 10 min,air cooling,staying at 720°C for 8h,and then at 50°C Cool to 620℃ every hour for 8 hours.Another solution treatment at980°C for 8 hours,cooling in air.Then pre-deformation cold drawing9.8%,14%,20%,and then stay in the furnace at 720°C for 8h,then cool to 620°C at 50°C for 8 hours,and finally cool to normal temperature in the air.The pre-deformed heat-treated specimens were placed in a SANS high-temperature creep machine for creep fracture experiments.The experimental results show that with the extension of annealing time at 930°C,the content of special grain boundaries in the matrix continues to increase.The peak value is reached when the holding time reaches 30 minutes.The creep fracture mechanism of GH4169 alloy shows that the mechanism of creep fracture is mainly divided into two types,one is the grain boundary slip,and the other is the grain boundary cavity nucleation mechanism.Under the lower stress(700MPa),the nucleation and growth process of voids occurred at the grain boundaries where the specimen mainly occurred,along with the slippage at the grain boundaries.At the same time,the annealing and heat preservation treatment after cold drawing shows high creep resistance.Under higher stress(810MPa),the creep fracture mechanism of the specimens that dominates the creep fracture is the slip of the grain boundary,accompanied by the hollow nucleation at the grain boundary.Annealing treatment after cold drawing did not improve the creep resistance of the alloy.At the same time,it was found that the alloy with the dominant cavity nucleation in the specimen has stronger creep resistance than the alloy with creep creep fracture at the grain boundary,and there is a certain correspondence with the distribution and proportion of the lowΣCSL grain boundary after pre-deformation heat treatment It shows that the pre-deformation heat treatment can optimize the grain boundary characteristic distribution of GH4169 alloy and enhance its resistance to creep. |
