LIU Yang1,2, XU Jing1, NING Ting1, YANG Hongyu1, TAN Zhenguo2, GUO Shibo1,2, WANG Mingbo1
(1. School of Mechanical Engineering, Hunan Engineering Research Center of Forming Technology and Damage Resistance
Evaluation of High-efficiency Light Alloy Components, Hunan University of Science and Technology, Xiangtan 411201, China;2. Hunan Xijiao Zhizao Technology Co., Ltd., Xiangtan 411100, China)
Abstract
Objective Laser powder bed fusion, as a new near-net forming technology, is a common additive manufacturing technology used to manufacture metal parts with flexible design and high resource efficiency. In the LPBF process, the parts are made layer by layer according to the CAD model of the parts. The laser interacts with the powder particles to form a three-dimensional solid structure. After the previous layer is formed, the building platform is lowered according to the thickness of the layer and a new powder layer is added. This process is repeated until the entire component is generated. Laser powder bed fusion technology has opened up a new technical approach for the design and manufacture of high-performance metal parts, which can solve the new challenges in materials, structure, process, performance and application in aerospace and other fields. In the metal additive manufacturing market, laser powder bed fusion occupies a considerable or even close to the dominant position. Due to its main advantages, including high material utilization, short production cycle, and not being limited by the geometry of the target part, etc., it is widely used in the processing and preparation of alloys. However, the main difficulty of LPBF is that it is easy to produce pores and cracks, resulting in poor forming quality and cannot meet the practical application requirements of industry. Therefore, it is necessary to optimize the process parameters of the superalloy to obtain a better relative density. At present, however, exploring a new material or obtaining the forming process for a certain part requires constant trial and error. Although the results obtained have high reliability, the process of constantly trying will cause a lot of time and resource consumption, which is very unfavorable to the development of materials and industrial applications. In the research process, the difficulty, efficiency and cost of process optimization should be considered, while the experimental design method and ANOVA can significantly improve the relative density at a low cost.
Methods The manufacturing of parts is affected by many process parameters, and the most commonly studied process parameters are laser power, scanning speed and scanning interval. These parameters have great influence on the final quality of LPBF samples. Many studies have investigated the relationship between process parameters and performance through simulation and experiment. In previous studies, these process parameters were studied independently by different researchers, and each parameter had an independent effect on the relative density, while the other parameters remained constant. The experimental design method and ANOVA have been proved to be effective methods to study the influence of multiple parameters in the processing of complex materials. The experimental design method is a statistical design technique of multi-factor optimization. By selecting a representative range of parameters to carry out orthogonal experiments, the influence of variables and levels are effectively determined using orthogonal array to achieve robust design and achieve the purpose of reducing research time and cost. ANOVA is the most commonly used statistical method, which can quantitatively analyze the influence of each LPBF parameter on the relative density, and determine the contribution rate of important parameters and relative density. At the same time, the influence of the interaction between various factors on the relative density can be comprehensively analyzed. Finally, the relationship model of laser power, scanning speed and scanning spacing of high-density alloy samples is established. According to the numerical simulation results, the process parameters of LPBF Inconel718 were optimized, and the effects of process parameters on the microstructure of LPBF Inconel718 superalloy were also studied. Finally, an efficient and stable laser powder bed fusion process of Inconel718 alloy was established by comparing the experimental results with the simulation results.
Results and Discussion According to the mathematical model established above, it is found that the scanning interval has the greatest influence on the relative density of the sample through calculation, and the contribution rate is 38. 31%. The second is scanning speed, the contribution value is 27. 73%; Finally, the contribution value of the laser power is 22. 51%. In the study range, the size of the molten pool is proportional to the density of physical energy, and the relative density model constructed in the relative density optimization is significant with R2 values of 0. 952 4, 0. 923 9 and 0. 872 4, respectively, for the relative density model. The proposed optimization method has higher acceptability and wider application fields. At the same time, the elemental analysis shows that Al and Ti elements have obvious microscopic segregation at the grain boundary, which can promote the cracking of liquid film and lead to the formation of cracks and other defects.
Conclusion The Inconel718 superalloy formed by LPBF has obvious epitaxial growth in the multi-layer molten pool with a large number of columnar grains growing in the xoz direction. Reasonable experimental design and corresponding mathematical model provide theoretical data support for the microstructure evolution of LPBF Inconel718 superalloy. The mathematical model established can effectively optimize and predict the density of LPBF forming parts. The optimization method is helpful to establish an efficient LPBF process to prepare Inconel718 alloy with high density and good quality.
Keywords:laser; powder bed fusion; inconel 718; microstructure; element segregation
Get Citation:LIU Y, XU J, NING T, et al. Process optimization and microstructure evolution of Inconel718 alloy by laser powder bed fusion[J]. China Powder Science and Techology, 2024,30(1): 23-35.
Received: 2023-09-15,Revised:2023-11-12,Online:2023-12-15。
Funding Project:国家自然科学基金项目,编号:52105334;湖南省重点研发计划项目,编号:2022GK2043;湖南省科技创新计划项目,编号:2021JJ40206,2022JJ20025,2022RC1134。
First Author:刘阳(1988—),男,副教授,博士,湖南省优秀青年基金获得者、 湖南省青年科技人才、 湖湘青年英才,硕士生导师,研究方向为激光增材制造技术及应用、 高温结构材料等。 E-mail: liuyang7740038@163.com。
Corresponding Author:王敏卜(1994—),女,讲师,博士,研究方向为激光增材制造技术、 粉末冶金等。 E-mail: 1054034127@qq.com。
DOI:10.13732 / j.issn.1008-5548.2024.01.003
CLC No:TG132. 3+2; TB4 Type Code:A
Serial No:1008-5548(2024)01-0023-13
