Cracking, Microstructure and Tribological Properties of Laser Formed and Remelted K417G Ni-Based Superalloy

Abstract

The K417G Ni-based superalloy is widely used in aeroengine turbine blades for its excellent properties. However, the turbine blade root with fir tree geometry experiences early failure frequently, because of the wear problems occurring in the working process. Laser forming repairing (LFR) is a promising technique to repair these damaged blades. Unfortunately, the laser formed Ni-based superalloys with high content of (Al + Ti) have a high cracking sensitivity. In this paper, the crack characterization of the laser forming repaired (LFRed) K417G—the microstructure, microhardness, and tribological properties of the coating before and after laser remelting—is presented. The results show that the microstructure of as-deposited K417G consists of γ phase, γ′ precipitated phase, γ + γ′ eutectic, and carbide. Cracking mechanisms including solidification cracking, liquation cracking, and ductility dip cracking are proposed based on the composition of K417G and processing characteristics to explain the cracking behavior of the K417G superalloy during LFR. After laser remelting, the microstructure of the coating was refined, and the microhardness and tribological properties was improved. Laser remelting can decrease the size of the cracks in the LFRed K417G, but not the number of cracks. Therefore, laser remelting can be applied as an effective method for strengthening coatings and as an auxiliary method for controlling cracking.

Effect of Mo Content on Microstructure and Mechanical Properties of Laser Melting Deposited Inconel 690 Alloy

“…During LMD, an argon gas stream was used as a delivery and protective atmosphere. Based on a series of preliminary experiments [30,31], the optimized process parameters used in this work are listed in Table 2. Inconel 690 plates with dimensions of 150 × 100 × 10 mm were used as substrates.…”

Tribology and Surface Engineering

“…Another example of laser beam application in surface engineering for repair cladding and shaping properties of surface layers was demonstrated by Liu et al [30]. Authors investigated the laser cladding of K417G Ni-based superalloy by analyzing the possibility of built-up cladding of worn turbine blades.…”

Synthesis and Characterization of Innovative Fe–Cr–Mn Ferritic Stainless Steel by Laser Powder Bed Fusion

“…Up to now, laser rescanning has been employed to tune microstructure [19,20] and reduce LPBF defects, especially porosity [21,22] in a variety of materials. The crack elimination with laser rescanning was studied for direct energy deposition process (DED) [23][24][25][26] but rarely reported for LPBF. [27,28] Ferritic stainless steels are not so frequently produced as austenitic stainless steel using LPBF.…”