scholarly journals Effect of Heat Treatment on Microstructure and Properties of 24CrNiMo Alloy Steel Formed by Selective Laser Melting (SLM)

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 631
Author(s):  
Yongsheng Zhao ◽  
Chenggang Ding
Keyword(s):  
Grain Boundary ◽  
Alloy Steel ◽  
Thermal Fatigue ◽  
Small Angle ◽  
Friction And Wear ◽  
Large Angle ◽  
Granular Bainite ◽  
Face Centered Cubic ◽  
Wear Properties ◽  
Thermal Fatigue Crack

The 24CrNiMo alloy steel powder was used as experimental material. The microstructure and mechanical properties of as-deposited, quenched and tempered (QT) and stress-relief annealed (SR) specimens were analyzed. The X-ray diffraction (XRD) analysis showed that the specimens in the three states were mainly ferrite (α-Fe), in which the as-deposited samples had puny face-centered cubic (FCC) structure Fe (γ-Fe). The microstructure observation showed that the as-deposited specimens were made up of ferrite, granular bainite, a small amount of cementite and residual austenite. The tensile test results indicated that the tensile strength and yield strength of the as-deposited specimens were 1199 MPa and 1053 MPa respectively, and the elongation at break was 10.7%. The elongation of QT and SR specimens increased to 11.6% and 12.8%, respectively. The electron backscattered scattering detection (EBSD) analysis results showed that the small-angle grain boundary content of the as-deposited samples was 58%, and large-angle grain boundary content was 15%. After QT and SR, small-angle and large-angle grain boundaries were obtained than those in the as-deposited specimens. The high-temperature friction and wear properties and thermal fatigue performances of the QT and SR specimens were improved significantly. The QT specimens had the smallest wear and thermal fatigue crack lengths, excellent resistance to friction and wear performance and prevention of crack growth, with an ideal comprehensive properties.

The Micro Structural Characteristic Parameters of High Grade Pipeline Steel and its Mechanical Properties

2006 ◽  
Author(s):  
Xiaoli Zhang ◽  
Chuanjing Zhuang ◽  
Lingkang Ji ◽  
Yaorong Feng ◽  
Wenzhen Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Pipeline Steel ◽  
Structural Parameters ◽  
Large Angle ◽  
Lower Bainite ◽  
Granular Bainite ◽  
High Grade ◽  
Pipeline Steels

The microstructure of high grade pipeline steels, including X65, X70, X80, X100, were studied by SEM and EBSD, respectively. It was found that the microstructures of high grade pipeline steels were composed of lower bainite, granular bainite and acicular ferrite. The phases of kinds of pipeline steels were composed of Fe3C, retained austenite and ferrite. And their percentage content, grain size and its distribution were studied respectively also. These micro structural parameters were correlated to the mechanical properties of kinds of pipeline steels. Furthermore, all kinds of angles of grain boundaries were studied, and the relationship between the angles of grain boundaries and mechanical properties was obtained. It was shown that as the improving of the steel grade, the grain boundary including small angle and large angle increased. And only when grain boundary was greater than 15 degree, it was effective to the toughness behavior.

Molecular Dynamics Simulation of the Effect of Large Angle and Small Angle Grain Boundaries on the Near-Threshold Fatigue Crack Growth in Iron

2004 ◽  
Author(s):  
Shiro Kubo ◽  
Masaki Misaki
Keyword(s):  
Molecular Dynamics ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Small Angle ◽  
Large Angle ◽  
Atomic Scale ◽  
Near Threshold

In the near-threshold region of the fatigue crack growth in metals, the amount of crack growth per cycle is in the order of the atomic scale. This may suggest that the near-threshold fatigue crack growth is controlled by atomic scale events. In previous papers the present authors applied the molecular dynamics to the simulation of near-threshold fatigue crack growth. In this study, the molecular dynamics method was applied to investigate the influence of inclined grain boundary on the near-threshold mode I fatigue crack growth behavior in BCC iron. Large angle grain boundaries served as an obstacle to the fatigue crack growth. Small angle grain boundaries had the effect of decreasing crack growth when the crack approached the grain boundary. When the crack reached the grain boundary it was trapped by the grain boundary.

Wear Life Prediction Model on 38CrMoAlA Alloy Steel

2010 ◽  
Vol 118-120 ◽  
pp. 681-685 ◽  
Author(s):  
Yu Tao Yan ◽  
Zhi Li Sun ◽  
Feng He Zhang
Keyword(s):  
Alloy Steel ◽  
Life Prediction ◽  
Friction And Wear ◽  
Design Method ◽  
Uniform Design ◽  
Wear Properties ◽  
Wear Life ◽  
Experimental Project ◽  
Uniform Design Method ◽  
Life Prediction Model

The wear experimental project on load and sliding speed was instituted by the uniform design method, the wear properties of 38CrMoAlA alloy steel under dry friction were investigated on a vertical universal friction and wear tester, the worn surfaces of specimens were observed by scanning electron microscope (SEM). The wear life predication model of 38CrMoAlA alloy steel was established by multiple regression analysis, and the significance of influencing factors was carried out. The results showed that the distribution of experimental points chosen by uniform design method was in research range, and the experimental efficiency was evidently increased, and the experimental cycle was shortened. The wear mechanism of 38CrMoAlA alloy steel was primarily abrasive wear and adhesive wear. It is found that the wear life predication model was highly significant.

Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ

1993 ◽  
Vol 51 ◽  
pp. 942-943
Author(s):  
J.-Y. Wang ◽  
Y. Zhu ◽  
A.H. King ◽  
M. Suenaga
Keyword(s):  
Grain Boundary ◽  
Lattice Mismatch ◽  
Weak Link ◽  
Coincidence Site Lattice ◽  
Large Angle ◽  
Dislocation Core ◽  
Superconducting Order Parameter ◽  
Outstanding Problem ◽  
Transmission Electron

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).

The Analysis on the Tribological Properties of TPU/PVC Blends under Oil Lubrication

2013 ◽  
Vol 774-776 ◽  
pp. 94-98
Author(s):  
Dao Yuan Pan ◽  
Peng Peng Wu ◽  
Zhong Xue Gao ◽  
Yu Zeng Zhang
Keyword(s):  
Working Conditions ◽  
Friction And Wear ◽  
Oil Lubrication ◽  
Wear Properties ◽  
Operation Conditions ◽  
Hydraulic Steering ◽  
Pros And Cons ◽  
Friction And Wear Properties ◽  
Lubrication Conditions ◽  
Better Than

Based on actual working conditions and parameters of the hydraulic steering gear, the purpose is optimizing the rubber seal of steering gear by different rubbers mixing technology. Compare the five kinds of rubber with metal of the friction characteristics in dynamic fit, it can obtain a performance excellent rubber real in the specific operation conditions. And then improve the overall service life of the steering gear. It is first prepared the same hardness TPU and PVC and blends that the ratio is 3:7, 5:5and7:3 in this article. The pros and cons of the five rubbers are analyzed in friction and wear properties of the above experimental. The test curve of coefficient friction and wear with time has been done under different load at constant low speed. It determines TPU/PVC = 3:7 blends through friction and wear and wear mechanism of five rubbers with steel comparatively analyses, and the heat resistance and wear resistance of them are better than the other TPU/PVC blends and PVC under oil lubrication conditions.

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