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18 pages, 6707 KiB

Open AccessArticle

The Effects of the Finishing Polish Process on the Tribological Properties of Boride Surfaces of AISI 4140 Steel

by Daniel Misael Flores-Arcos, Noé López-Perrusquia, Marco Antonio Doñu-Ruiz, Martin Flores-Martínez, Stephen Muhl Saunders, David Sánchez Huitron and Ernesto David García Bustos

Coatings 2025, 15(4), 474; https://doi.org/10.3390/coatings15040474 - 16 Apr 2025

Viewed by 274

Abstract

In sealing, sliding, and power transmission operations, surface quality and contact tolerances have high impacts on material system efficiency. Although the boriding process improves the wear resistance of metallic surfaces, it increases surface roughness, affecting the tribological efficiency of material systems. This study [...] Read more.

In sealing, sliding, and power transmission operations, surface quality and contact tolerances have high impacts on material system efficiency. Although the boriding process improves the wear resistance of metallic surfaces, it increases surface roughness, affecting the tribological efficiency of material systems. This study presents the tribological results of AISI 4140 boriding surfaces tested using a dehydrated paste pack boriding method with and without a finishing polish process to reduce the roughness. The duration of the boriding process was 1 h at 1123, 1173, 1223, and 1273 K using boron paste obtained from a commercial source and using a pot-polishing process with Al₂O₃ with a particle size of 0.5 μm for 25 min. The samples with and without the finishing polish process were structurally characterized using X-ray diffraction, and the boride coating adhesion was determined using Rockwell C indentation. The tribological properties of the boride surface with and without the finishing polish process were determined using a reciprocating sliding test, with a ZrO₂ ball as a counter body. The boride surfaces’ crystalline structure changed with polishing, which revealed the FeB phase and reduced the roughness value. These modifications in the surface characteristics altered the adhesion and tribological performance of the coating, resulting in a more stable tribological performance on the polished boride surfaces, with a reduction in the coefficient of friction (Cof) value from 0.75 ± 0.02 for the tribological test on the 1123 K-P sample to 0.59 ± 0.002 for the 1273 K-P sample surface at 20 N of applied load. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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20 pages, 10778 KiB

Open AccessArticle

The Effect of σ Phase Content on the Hot Working Properties of Super Austenitic Stainless Steel Containing 7Mo-0.42N

by Yanguo Li, Wanshuai Wang, Zhuyu Wang, Chen Chen and Zhinan Yang

Coatings 2024, 14(12), 1514; https://doi.org/10.3390/coatings14121514 - 30 Nov 2024

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Abstract

In the present study, super austenitic stainless steel containing 7Mo-0.42N was isothermally treated at 1100 °C, 1200 °C, and 1250 °C for different times, in order to obtain the samples with different σ precipitate content of 7%, 1.4%, and 0.7%. The effect of [...] Read more.

In the present study, super austenitic stainless steel containing 7Mo-0.42N was isothermally treated at 1100 °C, 1200 °C, and 1250 °C for different times, in order to obtain the samples with different σ precipitate content of 7%, 1.4%, and 0.7%. The effect of σ phase content on the hot working properties of the specimens was investigated under hot compression conditions at 900~1200 °C and strain rates of 0.01~5 s⁻¹. Results show that, with the increase in σ content, the recrystallized grains increase gradually, and the internal stress decreases firstly and then increases. Therefore, the σ phase has two roles in the thermal deformation process. One is that the σ phase promotes recrystallization and the other is that the σ phase hinders dislocation motion. In the hot working diagram of super austenitic stainless steel with different σ phase contents, the distribution of high power consumption and instability regions is significantly different. The sample containing 1.4% σ phase does not show the region where the power dissipation coefficient η is negative, and there is a large number of dynamic recrystallized grains in the high power region, showing good hot working performance. However, the local rheology and cracking in samples containing 0.7% and 7% σ phase after deformation are more serious. Combined with the constitutive equation, hot working diagram, and microstructure, it is found that the optimum hot working property of the super austenitic stainless steel containing 7Mo-0.42N could be obtained when it is deformed at a temperature of 1200 °C with a strain rate of 5 s⁻¹ when the content of σ phase is 1.4%. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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14 pages, 4991 KiB

Open AccessArticle

The Evolution of Surfaces on Medium-Carbon Steel for Fatigue Life Estimations

by Phanuphak Seensattayawong and Eberhard Kerscher

Coatings 2024, 14(8), 1077; https://doi.org/10.3390/coatings14081077 - 22 Aug 2024

Viewed by 1216

Abstract

Early in fatigue life, fatigue cracks are often initiated at persistent slip bands (PSBs), which play the main role in surface evolution when the components are subjected to cyclic loading. Therefore, this paper aims to study the behavior of the surface development of [...] Read more.

Early in fatigue life, fatigue cracks are often initiated at persistent slip bands (PSBs), which play the main role in surface evolution when the components are subjected to cyclic loading. Therefore, this paper aims to study the behavior of the surface development of medium-carbon steel, specifically 42CrMo4 (SAE 4140). Tests were conducted using tension–compression fatigue testing with stress amplitudes set at 30%, 40%, and 50% of the ultimate tensile strength (UTS); a load ratio of R = −1; and a frequency of f = 10 Hz. The ultimate number of test cycles was 2 × 10⁵. The fatigue test specimens with as-machined surface quality (Ra < 100 nm) were tested on a servo-hydraulic push–pull testing machine, and the tests were interrupted a few times to bring the specimens out for surface measuring with a confocal microscope. The linear roughness values of the arithmetic mean deviation (Ra), maximum height (Rz), maximum profile peak height (Rp), and maximum profile valley depth (Rv) were investigated and further used to determine the roughness evolution during cyclic loading (REC) by analyzing the inclinations of the fitting curves of roughness and number-of-cycles diagrams. REC could then be used to estimate and classify the fatigue lifetime. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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15 pages, 7964 KiB

Open AccessArticle

Nanoindentation Study on the Local Evaluation of Hydrogen-Induced Hardening Performance of Ferrite and Austenite in 2205 Duplex Stainless Steel: Experiment and Finite Element Modeling

by Ping Tao, Wei Zhou, Hongmei Liu and Xuedong Liu

Coatings 2024, 14(8), 1075; https://doi.org/10.3390/coatings14081075 - 22 Aug 2024

Viewed by 1380

Abstract

In this study, a combined experimental and finite element modeling methodology (FEM) for a nanoindentation study is presented to quantitatively investigate the influence of hydrogen on the mechanical properties of ferrite and austenite in 2205 duplex stainless steel. The experimental results showed that, [...] Read more.

In this study, a combined experimental and finite element modeling methodology (FEM) for a nanoindentation study is presented to quantitatively investigate the influence of hydrogen on the mechanical properties of ferrite and austenite in 2205 duplex stainless steel. The experimental results showed that, during hydrogen charging, the nano-hardness of ferrite and austenite gradually increased with time, showing a hydrogen-induced hardening phenomenon. After 3 h of hydrogen charging, the nano-hardness of both ferrite and austenite reached a saturation state, and the values of the nano-hardness of ferrite and austenite increased by 17.5% and 46.1%, respectively. FEM is employed by using a dual-phase microstructure-based model to reproduce nanoindentation load–displacement curves. To minimize the indentation size effect, an analytical correction model considering geometrically necessary dislocations (GNDs) was proposed. By considering GNDs, the errors between numerical predictions and experimental data reduced from about 50% to less than 5%. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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15 pages, 18868 KiB

Open AccessArticle

Carbon Atom Distribution and Impact Toughness of High-Carbon Bainitic Steel

by Xiaoyan Long, Zhao Dai, Wanshuai Wang, Zhinan Yang, Fucheng Zhang and Yanguo Li

Coatings 2024, 14(4), 457; https://doi.org/10.3390/coatings14040457 - 10 Apr 2024

Cited by 1 | Viewed by 1271

Abstract

High-carbon nano bainitic steel is currently a hot research topic. The effect of the matrix’s carbon content and carbon atom distribution on the toughness of high-silicon, high-carbon bainitic steel is studied. The microstructure under an incomplete austenitization process consists of undissolved carbides, bainitic [...] Read more.

High-carbon nano bainitic steel is currently a hot research topic. The effect of the matrix’s carbon content and carbon atom distribution on the toughness of high-silicon, high-carbon bainitic steel is studied. The microstructure under an incomplete austenitization process consists of undissolved carbides, bainitic ferrite, and retained austenite. Using this process, the carbon content in bainitic ferrite is relatively low. Under the complete austenitization process, the carbon content in the bainite ferrite in the sample is high, and there is more retained austenite in the blocky type. The sample exhibits high impact toughness under an incomplete austenitization process, which is mainly affected by the low carbon content of bainite ferrite, high coordination ability of retained austenite, and high interface density of microstructure. The EBSD results show that the crack easily propagates between parallel bainite laths with low interface density compared with the high interface density perpendicular to the laths. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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19 pages, 3828 KiB

Open AccessArticle

Comprehensive Fatigue Analysis and Practical Design Methodology for Weld Toes in the Sphere of Welded Hollow Spherical Joints in Grid Structures

by Yajie Yan, Saicong Guo and Zichun Zhou

Coatings 2024, 14(1), 50; https://doi.org/10.3390/coatings14010050 - 28 Dec 2023

Cited by 1 | Viewed by 1289

Abstract

This paper addresses the issue of fatigue in grid structures, a topic of interest in engineering and academia. The goal is to establish a practical fatigue design calculation method for weld toes in welded hollow spherical joints (WHSJs). The study focuses on commonly [...] Read more.

This paper addresses the issue of fatigue in grid structures, a topic of interest in engineering and academia. The goal is to establish a practical fatigue design calculation method for weld toes in welded hollow spherical joints (WHSJs). The study focuses on commonly used steel tube-WHSJs in grid structures, conducting 25 constant amplitude and four variable amplitude fatigue tests on tube–sphere joints (TSJs) to derive corresponding S-N curves. Using ANSYS, the hot spot stress concentration coefficient K_h at the weld toes in 22 TSJs was calculated, resulting in a numerical solution for K_h ranging from 2.0550 to 4.8600. Based on this, fatigue design methods were established using nominal stress amplitude and hot spot stress amplitude as fundamental parameters. Within a fatigue design reference period of two million cycles, the allowable nominal stress amplitude for TSJs is 22 N/mm², and the allowable hot spot stress amplitude is 66 N/mm². The study also conducted macroscopic and microscopic analyses on fatigue fractures of TSJs, revealing that the weld toe in the sphere of TSJs is the primary site for fatigue crack initiation. This research provides practical calculation methods for fatigue design in WHSJ grid structures, contributing to their broader application. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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18 pages, 8945 KiB

Open AccessArticle

Numerical Simulation and Experimental Study on Detecting Effective Prestress of 1860-Grade Strands Based on the Drilling Method

by Wenxiang Wu, Shunchao Chen, Chunyan Dong, Wenbai Peng, Jianzhou Yun and Liangpeng Nie

Coatings 2023, 13(11), 1869; https://doi.org/10.3390/coatings13111869 - 31 Oct 2023

Cited by 1 | Viewed by 1312

Abstract

In this paper, we study the magnitude of the effective prestressing force of steel strands in prestressed reinforced concrete structures. Through the theory of micro-hole release, the functional relationship equation between tensile stress and strain-containing coefficients A and B is established. Then, Midas [...] Read more.

In this paper, we study the magnitude of the effective prestressing force of steel strands in prestressed reinforced concrete structures. Through the theory of micro-hole release, the functional relationship equation between tensile stress and strain-containing coefficients A and B is established. Then, Midas FEA NX 2022 (v1.1) finite element software is used to establish the stress-release model of strand drilling holes and analyze the influence of parameters such as drilling depth, drilling diameter, hole–edge distance, and tension stress on the amount of stress release. Finally, through a homemade tensioning platform, we verify the reasonableness of the finite element simulation calculation law and determine coefficients A and B. The results of the study show that based on Kirsch’s analytical formula and the theory of microvia release, the axial tension force and axial strain are linearly correlated; the Midas FEA NX finite element software can effectively simulate the force state of strand cross-section; and through the strand-drilled hole model simulation and analysis, it is found that the tension stress value and the stress-release amount are related to the tensile stress value and the tensile stress value. We found that the value of tensile stress and the amount of stress released are positively correlated; with the increase in the hole margin, the amount of stress released gradually decreases; with the increase in the diameter of the hole, the amount of strain released gradually increases; and the greater the depth of the hole, the greater the amount of strain release. Moreover, the use of a hole margin of 3–6 mm, a hole diameter of 1.5 mm and 1.8 mm, and a hole depth of 2.5 mm is more reasonable in the test conditions, as follows. Through the drilling test conditions of 1.5 mm drilling diameter, 2.5 mm drilling depth, and 4 mm hole side distance, we verified the measured strain value of the steel wire and the tensile force value of the linear correlation between the functional relationship and the use of this functional relationship to determine the theoretical derivation of the coefficient to be determined: A is 1.12 and B is 57.84. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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13 pages, 5418 KiB

Open AccessArticle

Improved Wear Resistance of Nitro-Chromized Carbon Steel Using an Additional Carburizing

by Yue Hong, Shuqi Huang, Bin Deng, Yingmei Yu, Chupeng He, Wei Xu and Touwen Fan

Coatings 2023, 13(11), 1858; https://doi.org/10.3390/coatings13111858 - 29 Oct 2023

Cited by 1 | Viewed by 1239

Abstract

The controversial wear resistance limits the application of the nitro-chromizing process, which is a potential advanced chromizing strategy with a low chromizing temperature and thick strengthening layer. In this study, additional carburizing was proposed to optimize the nitro-chromizing process and the associated wear [...] Read more.

The controversial wear resistance limits the application of the nitro-chromizing process, which is a potential advanced chromizing strategy with a low chromizing temperature and thick strengthening layer. In this study, additional carburizing was proposed to optimize the nitro-chromizing process and the associated wear resistance. Samples of carbon steel were used to evaluate the optimized nitro-chromizing, normal nitro-chromizing, and other relevant processes. Comparative analyses were conducted through XRD composition analysis, microstructure observations, and mechanical property tests.The results confirm that the normal nitro-chromized sample has poor wear resistance due to severe abrasive wear, while the wear rate of the optimized nitro-chromized sample is only about 1/15 of that of the normal nitro-chromized sample. Both the above two samples have similar main phase compositions of Cr₂N and Cr₇C₃. However, the optimized nitro-chromized sample exhibits a lower friction coefficient and better adhesion strength than the normal nitro-chromized sample. The additional carburizing induces the formation of massive fine graphite sheets deposited on porous nitriding structures, which can be in charge of the low friction coefficient and good adhesion strength. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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14 pages, 7721 KiB

Open AccessArticle

Features of the Formation of Surface Structures under Dry Friction of Al-30Sn Composite against Steel

by Nikolay Rusin, Alexander Skorentsev and Maksim Krinitcyn

Coatings 2022, 12(9), 1309; https://doi.org/10.3390/coatings12091309 - 7 Sep 2022

Viewed by 1457

Abstract

Features of the frictional interaction of a sintered Al-30Sn composite, which is used as a coating of bearing inserts, with steel counterbody in the absence of liquid lubricant were studied. The tribological tests were carried out according to the pin-on-disk scheme at room [...] Read more.

Features of the frictional interaction of a sintered Al-30Sn composite, which is used as a coating of bearing inserts, with steel counterbody in the absence of liquid lubricant were studied. The tribological tests were carried out according to the pin-on-disk scheme at room temperature. The friction coefficient

μ

of the friction pair is increased up to approximately 0.6 during the running-in process. Its growth stops when the stage of steady state friction begins, and then

μ

fluctuates around some relatively high and constant value. The study of the friction surfaces of the friction pair showed that the aforementioned increase in

μ

is due to the formation of a discrete transferred layer on the friction track surface and strain hardening of the subsurface layer of the Al-30Sn sample under the action of hard particles of the transferred layer. It was established that tin is transferred on the friction track surface mainly in a composition of wear particles, despite the high content of the solid lubricant in the investigated samples. The wear intensity of the samples subjected to processing by equal channel angular pressing with route A is much lower than that of the sintered (unprocessed) ones. The main wear mechanism of Al-30Sn composites under dry friction against steel is a delamination of the highly deformed subsurface aluminum grains along their interphase boundaries. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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