Selective laser melting of Hastelloy X nanocomposite: Effects of TiC reinforcement on crack elimination and strength improvement

Abstract

The Hastelloy X (HX) nickel-based superalloy is increasingly applied in the aerospace industry because of its exceptional combination of oxidation resistance and hightemperature strength. The addition of nanoscale ceramic reinforcements to the HX alloy is expected to further improve its mechanical and thermophysical performance.The research challenge is to manufacture HX nanocomposites using additive manufacturing (AM) technologies, particularly selective laser melting (SLM), which has been used successfully to produce other nanocomposites. This paper systematically studies the microstructure and tensile performance of HX-3 wt.% TiC nanocomposite fabricated via SLM and explores the effects of TiC nanoparticles on hot-cracking elimination and strength enhancement. The findings reveal that the addition of 3 wt.% TiC nanoparticles resulted in (1) an extra 73 J/mm 3 laser-energy density needed to manufacture nearly full-density nanocomposite samples and (2) intergranular microcrack elimination due to the significant increase in grain boundaries induced by the grain refinement. The results showed a 17% increase in yield strength, while the elongation to failure was not significantly reduced. The results from the microstructure examination suggest that the strengthening mechanisms of load bearing and enhanced-dislocation density were the most pronounced mechanisms in the SLMfabricated nanocomposite. These findings offer a promising pathway to strengthen mechanical performance by addressing the hot-cracking issue in the AM of nickelbased superalloys that suffer from cracking susceptibility. The results can also help to accelerate the uptake of AM in high-performance and defect-free superalloys for various applications.

Microstructure performance enhancement of Si3N4 reinforced laser clad KF110 base composite coatings

“…TiN nucleated preferentially during the in situ reactions between Ti/N due to its high melting point. The tendency to micro‐cracks of this coating was increased due to the excessive content of Si 3 N 4 19–21 . Figure 1D indicates that the micro‐crack can be observed in Ti 5 Si 3 with high hardness/brittleness in specimen 2.…”

“…The tendency to micro-cracks of this coating was increased due to the excessive content of Si 3 N 4 . [19][20][21] Figure 1D indicates that the micro-crack can be observed in Ti 5 Si 3 with high hardness/brittleness in specimen 2. The thermal/internal stress were produced due to uneven shrinkage/expansion of the mixed powders, exceeding the tensile strength limit under the actions of difference of temperature gradient and the thermal expansion coefficient in LIP.…”

Fabrication of (SiC-AlN)/ZrB2 Composite with Nano-Micron Hybrid Microstructure via PCS-Derived Ceramics Route

“…The MGS was 97 nm. Such presence of nano-scale grains had a strong influence in enhancing the mechanical properties of the (SiC-AlN)/ZrB 2 composite [ 39 ]. When the temperature further increased, the elongated crystal grains further increased, and the MGS also increased with the temperature increase ( Figure 4 c,d).…”

Toward the Understanding of CoAl2O4 Additions on the Formation of Microstructure in Alloy 718 Processed by Laser Powder Bed Fusion

“…It has been widely reported that the additively manufactured Ni-based metal matrix composites (MMC) can achieve partial CET with the presence of various ceramic particles. [25][26][27][28][29][30][31][32] Among these candidates, CoAl 2 O 4 is believed to be capable of triggering grain refinement in Ni-base superalloys by interacting with reactive elements such as Cr, Ti, and Nb in the melt pool and forming elemental Co. [33,34] Previous studies have shown that a subtle addition of CoAl 2 O 4 (e.g., 0.2 wt pct) contributes to refining the grain size and reducing the degree of elastic anisotropy within L-PBF processed Alloy 718 when optimized scan parameters and 67 degree of scan rotation were applied. [35,36] The resulting oxides distributed with the microstructure were also found to impede the movement of grain boundaries during heat treatment.…”