Microstructure And Properties Of Laser Melting Deposited Tungsten Alloy

The development of Laser Melting Deposition(LMD)technology has opened up a new possibility for the rapid preparation of tungsten alloys has large-sized and complex structural.In this paper,80W-20Fe binary alloy samples with and 90W-7Ni-3Fe ternary alloy samples were prepared by LMD technique.The influence of process parameters on the microstructure of W-Fe and W-Ni-Fe alloys prepared by LMD technology was discussed.The formation mechanism of microstructure of tungsten alloy under laser irradiation was discussed.The 90W-7Ni-3Fe samples were coMPared with the liquid phase sintered samples of the same composition.According to the research of 80W-20Fe alloy,the samples contain three phases of W,Fe and Fe7W6.The intermetallic compound Fe7W6 is a peritectic reaction product in the process of non-equilibrium solidification.The Fe7W6 phase forms a gray shell on the surface of the W phase,or is scattered in the black Fe matrix to form a gray pattern.The W phase exists in the form of particles or dendrites.The tungsten particles are unmelted or partially melted raw W powder,and the tungsten dendrites are deposited solidification of supersaturated W in liquid Fe.When input energy density is greater than 150 J/mm3,the dendrite structure appears,and with the energy density increases,the proportion of dendrites increases.The formation of the intermetallic compound Fe7W6 and W dendrites significantly increases the hardness and brittleness of the sample.The study of LMD 90W-7Ni-3Fe alloy found that when the laser power is less than 800 W during the preparation process,there are a large number of holes in the samples.The amount of holes decreases with increasing laser power,when the laser power is 900 W,the density of the sample can reach 99,6%.Two phases of W and(Fe,Ni)were found in all samples,and W phase is divided into W particles and W dendrites.A small amount of W dendrites were generated when used high power processing,and W particles or dendrites were uniformly distributed on the bonding phase(Fe,Ni).CoMPared with liquid phase sintered samples,LMD samples are similar in morphology,with higher hardness and tensile strength,but lower elongation In order to improve the elongation of the LMD sample,annealing and hot isostatic pressing treatment were tried,but the elongation was not improved.