A Promising Pressurized Duplex Manufacturing Route of High Nitrogen Stainless Steel

AISI M42 is a Mo-series high-speed steel (HSS) with an additional 8 wt% Co that exhibits high hardness and strength, superior red hardness and wear resistance, and good toughness. [1][2][3] It is well suited for making cutting tools, particularly those used to machine difficult-to-machine materials. [4,5] The continuous emergence of novel highperformance materials and the growing demand for high machining efficiencies have led to an increase in the requirements for cutting tools. [6,7] Therefore, it is imperative to further improve the properties of M42 HSS.The addition of alloys has been reported to be an effective way to improve the properties of HSS. [7][8][9][10][11][12][13][14][15][16][17] For instance, proper Al addition can improve the tempering resistance of high-boron HSS. [8,9] The appropriate addition of Si, Ti, or Nb can improve the secondary hardness and bending strength of W-Mo-Cr-V HSS (e.g., M2 and M7). [10,12,13] Appropriate rare earth addition can improve the impact toughness of M2 HSS and highcarbon HSS. [7,[14][15][16] Recently, the addition of nitrogen (N) to HSS has also been explored. Wang et al. and Hara et al. reported that the addition of N could reinforce the secondary hardening of semi-HSS and high-carbon HSS due to the precipitation of fine carbonitrides. [18,19] Cieśla et al. improved the carbide distribution of M2 HSS by N-alloying, thus enhancing its brittle cracking resistance. [20] Mattar et al. reported that adding N could enhance secondary hardness and wear resistance of M41 HSS. [21,22] Therefore, N-alloying is a promising method for improving the properties of HSS. However, few reports exist on the application of N in M42 HSS, particularly regarding the effect of N on the properties of M42 HSS. In addition, the N

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Exploring the Influence Mechanisms of Tempering Temperature and N‐alloying on Mechanical Properties of AISI M42 High‐Speed Steel

Jiao

Feng

et al. 2023

“…Both N-free and high-nitrogen (0.18 wt%) M42 HSS were fabricated by a duplex melting route of pressurized induction melting and pressurized electroslag remelting. [29,30] The chemical compositions of the two steels are listed in Table 1. The induction melting and electroslag remelting processes were performed under high argon pressure for N-free steel and high-nitrogen pressure for 0.18N steel.…”

Section: Materials Preparationmentioning

confidence: 99%

Improved High‐Temperature Softening Resistance and Wear Resistance of AISI M42 High‐Speed Steel by N‐Alloying

Jiao

Feng

et al. 2023

Self Cite

Herein, a novel high‐nitrogen (0.18 wt%) M42 high‐speed steel is fabricated by pressurized metallurgy. The high‐temperature softening resistance of N‐free and 0.18N steels is evaluated by hardness measurement at room temperature after additional heating at 600 °C for various times, and the high‐temperature wear resistance is evaluated by ball‐on‐disk dry sliding wear test at 600 °C. The microstructure is characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), and high‐resolution transmission electron microscope (HRTEM). The results indicate that the hardness of 0.18N steel is 2–3 HRC higher than that of N‐free steel after additional heating at 600 °C for 4–120 h. The superior high‐temperature softening resistance of 0.18N steel is primarily ascribed to the smaller coarsening rate of M2C secondary carbides. Under the dry sliding condition at 600 °C, the wear rate of N‐free steel is approximately 1.5 times higher than that of 0.18N steel. The better high‐temperature wear resistance of 0.18N steel is primarily because the superior softening resistance makes it maintain higher hardness during the wear process to provide stronger support for the oxide layer and increase the protective ability of oxide layer to steel.

Cerium Addition Improves Cleanliness and Refines Microstructure of As‐Cast High‐Nitrogen Stainless Bearing Steel

Lu,

Feng,

et al. 2023

Self Cite

High‐nitrogen stainless bearing steel (HNSBS) is the most representative third‐generation aviation bearing steel, and the cleanliness and microstructure characteristics of bearing steel are crucial to its high performance and long service life. In this work, the effect of cerium addition on the cleanliness and microstructure characteristics of as‐cast HNSBS was systematically studied by combining microstructural characterization and thermodynamic analysis methods. The results show that with increasing Ce content, the cleanliness of steel first improved and then decreased, and Ce2O2S, Ce2O3 and CeN inclusions were generated successively. The Ce content should be controlled to ≈0.012 wt% to ensure that all Al2O3, MgO · Al2O3, and MnS inclusions were modified, and minimize the formation of large‐size Ce‐bearing inclusions. Furthermore, cerium addition refined the dendrite structure due to more nucleation sites for γ‐Fe and the enrichment of Ce in the liquid phase at solidifying front. The finer and more dispersed distribution in precipitates was ascribed to the reduction of growth space and Cr segregation, as well as the increase in effective nucleation sites. These results can offer theoretical guidance for inhibiting the formation of harmful inclusions in high‐nitrogen alloy systems and refining the microstructure of alloy systems containing M23(C, N)6 and M2(C, N) precipitates.