Study on the Dissolution and Precipitation Behavior of Self-Designed (NbTi)C Nanoparticles Addition in 1045 Steel

Abstract

Self-designed (NbTi)C nanoparticles were obtained by mechanical alloying, predispersed in Fe powder, and then added to 1045 steel to obtain modified cast steels. The microstructure of cast steels was investigated by an optical microscope, scanning electron microscope, X-ray diffraction, and a transmission electron microscope. The results showed that (NbTi)C particles can be added to steels and occur in the following forms: original ellipsoidal morphology nanoparticles with uniform dispersion in the matrix, cuboidal nanoparticles in the grain, and microparticles in the grain boundary. Calculations by Thermo-Calc software and solubility formula show that cuboidal (NbTi)C nanoparticles were precipitated in the grain, while the (NbTi)C microparticles were formed by eutectic transformation. The results of the tensile strength of steels show that the strength of modified steels increased and then declined with the increase in the addition amount. When the addition amount was 0.16 wt.%, the modified steel obtained the maximum tensile strength of 759.0 MPa, which is an increase of 52% compared with to that with no addition. The hardness of the modified steel increased with the addition of (NbTi)C nanoparticles. The performance increase was mainly related to grain refinement and the particle strengthening of (NbTi)C nanoparticles, and the performance degradation was related to the increase in eutectic (NbTi)C.

Effect of (NbTi)C Particles on the Microstructure and Hardness of High Chromium and Nickel Indefinite Chilled Cast Iron

“…It can be seen from the microstructure that the sizes of the austenite and carbides decreased after adding (NbTi)C particles (Figure 1), and the main reason for this structural transformation may be because the (NbTi)C particles can be used as the nucleation core of austenite, which increases the nucleation probability of austenite. Previous studies have confirmed that the addition of (NbTi)C particles can host the nucleation position of austenite in carbon steel [18][19][20], and that the (NbTi)C particles can hinder the growth of primary austenite grains. In addition, research has shown that the added particles also have a certain refining effect on carbides in cast iron [21,22].…”

“…Before smelting, the crucible was wrapped with a glass fiber cloth with a temperature resistance of 2000 • C to prevent the melt flowing out and damaging the cooling system due to the crack of the crucible during the smelting process. The preparation process of self-designed (NbTi)C particles has been introduced in detail in the literature [18][19][20]. Commercially available Nb powder, Ti powder (purity 99.5 wt % and particle size ≤ 40 µm), and graphite powder (purity 99.5 wt % and particle size ≤ 4 µm) were used as raw materials.…”

First-Principle Study on the Stability of Lightly Doped (Nb1–xTix)C Complex Carbides and Their Verification in 1045 Steel

“…Take the sample at half the radius of the ingot, observe the added (NbTi)C particles with FEI Tecnai G 2 F30 TEM, and identify the composition and structure of the particles through the attached energy-dispersive spectrometer (EDS) and selected area diffraction pattern (SADP). The detailed experimental method, process, and conclusion have been published in previous articles. − …”