The New Iron-based Alloy Powder And Oxygen Content Controlled Study

Recently, the research shows that there can formed strengthening phase which in form of nano-cluster size in dozens nanometer, these strengthen phase exhibits excellent stability in high temperature, which can improve the working temperature of Fe-based alloy by above 100℃, this is a important research progress on Fe-based superalloy, and the strengthen phase is compose of Ti, Y, O and vacancy, and it is formed by means of powder metallurgy process. In previous studies, we obtain the structure by means of mechanical alloy, the study on the material restricted to testing stage. So the preparation of Fe-based alloy powder is premise of its application. This article prepare the powder by gas atomization, and explore the effect of atomization medium, process and the way that oxygen element is introduced in the powder on the component, particle size, morphology and the existing state of oxygen element in the particle.According to high melting point and insufficient liquidity of Fe-based alloy, we explore the characteristic of back pressure of metal guide tube in the atomization nozzle. By contrast, we found that there is always stable negative pressure in column tube during atomization, but to taper tube, the pressure will be positive value when the atomization pressrue become higher, while the pressure of column tube is more negative. So column tube is good to the stable proceeding of atomization. This article choose column shape tube and optimize the parameter of the metal guide tube, the length of tube tip is in the range of 2.1-2.3mm, and the atomization pressure is in the range of 3.0-4.OMPa.During the preparation of Fe-Cr-W alloy ingot, we found time and temperature have effect on the content of Y, the loss of Y element is increases while the smelting temperature increases and holding time is prolonged. When the smelting temperature increase from 1600℃to 1700℃, the content of Y element decrease from 0.32wt% to 0.05wt%, this result provide reference to the atomization. The result of atomization shows that the increase of superheat and atomization pressure can reduce the median particle size, and increase the yield of fine powder(-45μm). When the atomization pressure increase from 3.0MPa to 3.5MPa, the median particle size d50 reduce from 45.7μm to 36.1μm. But the effect of increase in atomization pressure on the reduction of particle size is more obvious. The SEM shows that the morphology of powder is sphere, and there is satellite particle, the influence of change in atomization pressure and superheat on powder morphology is slight.Mix the atomization gas with Ar and O2 can introduce oxygen element to the powder, the analysis shows the relationship between content of O2 in the gas and content of oxygen element in the powder is linearity. When the volume ratio of O2 in the gas increase from 0.45% to 0.6%, the content of oxygen element increases from 0.31% to 0.41%. The relation between content of oxygen in the powder and median particle size is inverse. By the method of EDAX, we found the content of oxygen increaseing from centre to surface of the particle, which shows that the O2 diffusion from surface to the centre. The article also explore the increase and existing mode of oxygen element in the powder oxidated by heat, the result of cyclic oxidation test under 500℃and 600℃shows that in the beginning of oxidation, the content of oxygen element increase slightly, when heat for some time, the oxidation process is accelerated, and the improve of temperature accelerate the oxidation process more deeply, but the increase in content of Y element can slow down the oxidation process.XRD shows in the powder oxidated by heat, the main product phase is oxide, because the oxidation take place in the surface of the powder, it is difficult to introduce oxygen element into the inner of powder. In the XRD of powder that oxidated during atomization, no oxide phase is found, so by contrast the two oxidated ways, we found the oxygen element exist main in solid solution state in powder oxidated during atomization.