THE only addition to this issue of “Steel and its Heat Treatment” is a chapter on nitriding, contributed by Dr. V. O. Homerberg. In the space of sixteen pages a brief outline is given of the nature and conduct of the nitriding process, of the steels suitable for nitriding, and of their properties after treatment. Otherwise the book remains the same, although eight years have passed since the preparation of the previous edition. There is still, therefore, no reference to the notched-bar impact tests to which British metallurgists rightly attach so much importance, to grain size control (although this originated in America), to the newer types of stainless steels, or to manganese -molybdenum steels.Steel and its Heat TreatmentD. K.BullensBy. Third edition, rewritten and reset. Pp. xiii + 580. (New York: John Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1935.) 25s. net.

Steel and its heat treatment

This study investigates the mechanism driving the formation of core-shell carbides during laser metal deposition (LMD). The interaction between CFs and 316L metal powder under laser irradiation results in the formation of new composite materials (316L/CFs) because of two-phase (solid-liquid) melting. 316L/CFs comprise a metal matrix with M7C3 and M23C6 carbides. The metal matrix also contains raw 316L powder particles. The composites thus obtained (316L/CFs) were characterized using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and microhardness studies. The characterization revealed an in-situ transformation of M7C3 carbides to M23C6, which either occurs completely or ceases during transition stages resulting in the formation of core-shell carbides. The morphological analysis illustrates that primary carbides are of core-shell types with a single-crystal lattice. Moreover, the heat treatment can be used for the coalescence, coagulation, and partial dissolution of eutectic M23C6 carbides. It was observed that the morphology of eutectic and prime carbides are altered during the heat treatment at 1050 °C (4 h) and smooth cooling to 350 °C (11 h). Thus, the transformation of Cr7C3 (skeletal) → Cr23C6 (skeletal) → Cr23C6 (globular) occurs. Furthermore, the characterization of heat-treated samples confirms the core-shell nature of carbides. On the other hand, the core microhardness decreased by 1.5 times compared to that of the shell.

Investigation of M7C3, M23C6 and M3C carbides synthesized on austenitic stainless steel and carbon fibers using laser metal deposition

Balance between strength and ductility of dilute Fe2B by high-throughput first-principles calculations

Microstructure evolution and mechanical anisotropy of M50 steel ball bearing rings during multi-stage hot forging

Gradient microstructure evolution and hardening mechanism of carburized steel under novel heat treatment

A new annealing process, spheroidation-critical annealing, was designed to optimize the properties of carburized steel 15CrNiMo instead of the traditional process. In this study, four factors and three levels of orthogonal experiment were used to design annealing experiments with different parameters, and the optimal combination of performance was obtained, giving consideration to both surface hardness and core toughness. After complete heat treatment, the vickers hardness of the surface of experimental steel could reach 752HV, and the impact energy of the core could reach 175 J/cm2. On this basis, the effects of new annealing process and traditional high temperature tempering process on the machinability of the experimental (the surface hardness of the experimental is taken as the performance index after the treatment of the two processes) are studied. At the same time, the effects of two processes on the surface hardening mechanism and core toughness of subsequent quenching and tempering processes of experimental steel are discussed. The results show that the new annealing process can hardly reduce the cutting property of the surface of experimental steel (after two kinds of process, the surface of the experimental steel vickers hardness is 302 HV and 325 HV), through the way of stable carbides, promote the quenching process of experimental steel surface high carbon martensite hardened, promoted 70 HV hardness compared with the traditional process. However, the toughness of the experimental core is insensitive to the two processes, so the new process can improve the surface hardness without reducing the toughness of the experimental.

The novel process of spheroidizing-critical annealing used to optimize the properties of carburized steel and its effect on hardening mechanism of quenching and tempering

Hypereutectic high chromium cast iron (HHCCI) possesses excellent thermal deformation potential, although it is difficult to deform at room temperature. It can release stress through the fracture of primary M7C3 (P-M), and the softened eutectic structure has a self-healing effect on the cracks to ensure the continuity of material. The morphology of the P-M is very irregular, with the distinct relative dimensions between P-MH ((001) plane//compression plane) and P-ML ((100) or (110) plane//compression plane). From TEM and SEM characterizations, the crack propagation site of P-ML is consistent with the interface of internal multidirectional stacking faults. The fractures of P-ML extend along the (100) (or (110)) and (001) planes during room-temperature and hot compression, respectively. This difference is contributed to the change of the stress state of P-ML by softened austenite and the improvement of the deformation ability of P-M itself. In addition, the anisotropic hardness and strain hardening behavior of P-ML and P-MH were also contributed to the anisotropy of internal stacking faults.

The relationship between fracture mechanism and substructures of primary M7C3 under the hot compression process of self-healing hypereutectic high chromium cast iron

Shengrui Su

Papers

The novel process of spheroidizing-critical annealing used to optimize the properties of carburized steel and its effect on hardening mechanism of quenching and tempering

The relationship between fracture mechanism and substructures of primary M7C3 under the hot compression process of self-healing hypereutectic high chromium cast iron

Hot Deformation Behavior of V–Ti Microalloy Steels

Crystallographic insights into the role of nickel on hardenability of wear-resistant steels

Gradient microstructure evolution and hardening mechanism of carburized steel under novel heat treatment