Effect of Ti+Al Content on the Microstructure and Properties of Laser Additive Specimens of IN718 Alloy
To improve the mechanical properties and service temperature of laser additive IN718 alloy com-ponents,five improved IN718 laser additive samples with the gradient increase in Ti+Al content were pre-pared.The mechanical properties at room temperature and high temperature and microstructure of the samples were studied by universal testing machine,SEM,XRD,and JMatpro software.The results indicate that as the Ti+Al content increases,the proportiaon of γ'phase gradually rises,with an increase in room temperature strength and a significant decrease in elongation.When the content of Ti+Al reaches 7.6％,the proportion of γ'precipitated phase is 5 times that of γ phase and the hardness is 55.6 HRC.Then the abundant precipitation of brittle phases results in the initiation of cracks.After undergoing 1 100 ℃×1 h+850 ℃×8 h heat treatment,the high-temperature strength of the samples at 850 ℃ initially increases and then decreases with the increasing Ti+Al content.And when the content of Ti+Al arrives at 5.6％,the high-temperature yield strength and elongation of the samples reach the maximum value of 553 MPa and 12％,respectively,showing consistency in all directions.Meanwhile,the proportions of γ'precipitated phase and γ phase are close(41.5％and 39.9％,respectively).In subsequent research,the Ti+Al content in standard IN718 alloy can be increased to 5.6％,and properly using γ'strengthening can obtain excellent high-temperature mechanical properties and compatibility of laser additive process.
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