Gain Boundary Structure And Performance Optimization Research Of Hastelloy C-276

Due to its good high temperature strength,resistance to neutron radiation,and perfect anti-oxidation ability,Hastelloy C-276 has been widely used in the field of chemical,oil,nuclear industry and so on in the last four decades.Recently,Hastelloy C-276 become one of the candidate material for fuel cladding.In order to face the harsh working environment,Hastelloy C-276 requires more excellent mechanical properties and corrosion resistance.To improve the performance of the material in through a effective process is the main goal of this paper.Grain boundary structure has long been known to play a critical role in many material properties,such as precipitation,corrosion,and cracking.Grain boundary engineering(GBE),which was under the light of “grain boundaries design and control” proposed by Watanabe,developed a lot and was fruitful during the last two decades.The grain boundaries related properties of materials can be enhanced by exercising control over the population of low ?CSL grain boundaries,as defined by the coincident site lattice(CSL)model.A large body of works proved that the grain boundary character distribution can be altered via proper thermomechanical treatments.Some face-centered cubic meta materials with low to medium stacking fault energy,such as Pb-base alloy,Ni-base alloy,OFE cooper,and austenitic stainless steel,were successfully applied this concept to promote ?3n boundaries formation,and their properties were greatly enhanced.This may be an approach to further improve the resistance to intergranular corrosion of Hastelloy C-276 which is also a f.c.c material with low stacking fault energy.The effects of thermomechanical treatments on GBCD in Hastelloy C-276 were studied by using scanning electron microscope(SEM),electron backscatter diffraction(EBSD)The effects of rolling deformation on the grain size of Hastelloy C-276 were also investigated.The intergranular corrosion resistance of Hastelloy C-276,which has different special boundaries,was studied by using ASTM G28-A.the high temperature mechanical performance of Hastelloy C-276 was researched at 650 ? with an universal high-temperature materials testing machine.It is possible to reach the following general conclusions that are given below:1.The ratio of special boundaries in Hastelloy C-276 can be improved by using Grain Boundary Engineering method.2.In Hastelloy C-276,small strain(10%)and subsequently high temperature(1120?)annealing for short time(5min)can produce high proportion of low?CSL grain boundaries(more than 55%),which mainly are ?3n(according to Brandon's criterion).3.As the rolling deformation increases,the ratio of special boundaries of Hastelloy C-276 decreases;and the grain size increases;the performance on resistance to intergranular corrosion was evaluated using ASTM G28-A method,and results show that weight loss of specimens with 10% deformation reaches the minimum.4.The high temperature tensile fracture mode of Hastelloy C-276 is ductile fracture after using Grain Boundary Engineering method.