| W-Ni-Fe refractory alloy is widely used in national life due to its high density,high strength,good toughness and other excellent properties.It is used in weapon industry,such as armor-piercing bomb,armor-piercing bomb and explosion-piercing bomb,gyroscope outer rotor which can be used as navigation instrument in aerospace field,and shielding material for radiation protection in nuclear industry.Therefore,W-Ni-Fe refractory alloy is a very important strategic material.However,the properties of W-Ni-Fe refractory alloy are seriously affected by these elements,such as the high melting point,the difficulty in sintering and the limitations of process and technology,which restrict the application range of the refractory alloy.Therefore,it is of great practical and strategic significance to develop a new sintering technology and prepare W-Ni-Fe refractory alloy with excellent properties,fine grain size and uniform structure.In this paper,the 90W-7Ni-3Fe refractory alloy is taken as the research object,and oscillating pressure sintering is used to sinter the 90W-7Ni-3Fe refractory alloy powder.At the same time,the oscillating pressure sintering technology is based on hot pressure sintering and it uses the oscillating pressure of certain frequency as the driving force for sintering.The driving force for oscillating pressure sintering is a dynamic pressure,which is different from the traditional constant isostatic pressure.However,this also shows that the oscillating pressure sintering technology is closely related to the traditional hot pressure sintering technology.Therefore,in this paper,two sintering technologies,i.e.oscillating pressure sintering and hot pressure sintering,are used to sinter the 90W-7Ni-3Fe refractory alloy powder,then the samples are analyzed and compared.From the point of view of sintering temperature and sintering time,the samples made by the two sintering processes are tested for their properties,including the microstructure,grain size,density and hardness.In addition,according to different sintering temperatures,samples with good properties have been heat treated to investigate the influence of element diffusion on the properties of samples.Through analysis,on the one hand,the comparison between the two sintering processes is carried out;on the other hand,the connection among the two sintering processes,microstructure and properties is explored and compared.Finally,the advantages of oscillatory sintering are verified,and the oscillatory sintering technology has great advantages in restraining grain growth,improving sintering density and reducing sintering temperature.Through experiments,the required temperature for obtaining high density(>99%)samples by oscillatory pressure sintering is about 100? lower than that by hot pressure sintering under different temperatures.At the same temperature,the density of samples prepared by oscillatory pressure sintering is always higher than that of samples by hot pressure sintering.Oscillatory pressure sintering also inhibits the growth of grains,and the activation energy of grain growth is about 6 times lower than that of hot pressure sintering.At the same time,the sample after heat treatment also shows that element diffusion has a great influence on the properties of the sample,while oscillatory sintering technology can promote element diffusion.Samples sintered by oscillating pressure sintering under different holding time have higher density than those prepared by hot pressure sintering under the same holding time and have relatively homogeneous microstructure.At the same time,the samples sintered by oscillating pressure sintering have relatively fine grains compared with those prepared by conventional hot pressure sintering technology.The grain size and hardness are also slightly higher than those of samples prepared by hot pressure sintering.This shows that oscillating pressure sintering technology is an efficient and high performance sintering technology for refractory alloys. |
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