Effect of Laser Remelting on Cladding Layer of Inconel 718 Superalloy Formed by Laser Metal Deposition.

Bo Xin,Xiaoqi Wang,Lida Zhu,Yadong Gong,Jiangyu Ren

doi:10.3390/ma13214927

Abstract

The brittle phase (Laves) of Inconel 718 parts formed by laser metal deposition (LMD) represents a bottleneck of the engineering applications. In order to investigate effectiveness of laser remelting (LR) technology on suppressing the formation of Laves phase, different laser scanning speeds of the LR process were adopted to build and remelt the single-pass cladding layers. The evolution of phase composition, microstructural morphology, and hardness of the LMD and LMD + LR specimens were analyzed. The experimental results show that different laser scanning speeds can obviously change the microstructural evolutions, Laves phase, and hardness. A low laser scanning speed (360 mm/min) made columnar dendrite uninterruptedly grow from the bottom to the top of the cladding layer. A high laser scanning speed (1320 mm/min) has a significant effect on refining Laves phase and reducing Nb segregation. When the laser scanning speed of LR process is equal to that of LMD, the cladding layers can be completely remelted and the content of Laves phase of the LMD + LR layer is 22.4% lower than that of the LMD layer. As the laser scanning speed increases from 360 to 1320 mm/min, the mean primary dendrite arm spacing (PDAS) values of the remelting area decrease from 6.35 to 3.28 μm gradually. In addition, the low content of Laves phase and porosity contribute to the growth of average hardness. However, the laser scanning speed has a little effect on the average hardness and the maximum average hardness difference of the LMD and LMD + LR layers is only 12.4 HV.

Highlights

Laser metal deposition (LMD) process is an additive manufacturing technology that is useful for the production of large or high-valued metal components in a short production cycle [1]
The laser remelting (LR) process is beneficial to the reduction of segregation phase
The effect of laser remelting on cladding layer of Inconel 718 superalloy formed by laser metal deposition was studied in this paper

Summary

Introduction

Laser metal deposition (LMD) process is an additive manufacturing technology that is useful for the production of large or high-valued metal components in a short production cycle [1]. By utilizing a high-energy laser, a molten pool is formed by melting the alloyed spherical powder ejected from several nozzles, and rapidly solidifies to deposit cladding layers. LMD has been successfully employed to form many types of metallic materials and applied in aeronautics, astronautics, mould, etc. LMD of Inconel 718 Ni-based superalloy has attracted much attention because of the benefits of excellent high-temperature creep resistance and good metallurgical bonding with less heat-affected zone when compared to traditional metal joining processes [2]. The Inconel 718 superalloy has excellent heat resistant performance (650–1000 ◦ C) and stress-corrosion resistance [3,4,5].

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