Mustafa Ulutan

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

In this study, the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been evaluated. Sample surfaces of AISI 4140 steel were treated by quenching, carburizing, boronizing and plasma transferred arc (PTA) modification. The microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy (SEM). The mechanical properties of the samples including the surface roughness, microhardness, and abrasive and adhesive wear characteristics were also evaluated. Wear tests were applied by using a block-on-disc configuration under dry sliding conditions. The wear behavior and friction characteristics of the samples were determined as a function of sliding distance. Each sample group was compared with the other sample groups, and it was observed that the carburized samples demonstrated the lowest weight losses; however, PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.

Microstructure and Wear Behavior of TIG Surface-Alloyed AISI 4140 Steel

In this study, AISI 4140 steel surfaces were alloyed with preplaced SiC/C powders using a tungsten–inert gas (TIG) heat source. The effects of different production parameters on the microstructure, hardness, and wear resistance of the alloyed surfaces were investigated. Following the surface alloying, conventional characterization techniques such as optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to study the microstructure of the alloyed surfaces. Hardness measurements were performed across the alloyed zones, and wear properties of the alloyed surfaces were evaluated using a block-on-disc wear test method. The collected data suggest that alloyed zones solidify into different microstructures depending on the production parameters. The alloyed surfaces exhibited an increase in hardness and wear resistance; this was attributed to the presence of harder phases and graphite. Lamellar or layered crystal structures of graphite have good lubricity and decrease coefficient of friction. Hardness values of the alloyed surfaces varied between 670 and 1165 HV. The minimum mass loss was observed in the sample that was alloyed with a 0.0581 cm/s process speed, 0.5/0.2 g/s powder feed rate, and a 29.1 kJ/cm heat input. The exhibited mass loss ratio was attributed to M3C, M7C3, and FeSiC carbides in the microstructure. The results conclude that TIG can be used effectively for surface alloying with SiC/C powders to improve the wear resistance of the AISI 4140 steel surface.

Effect of cryogenic treatment on tribological behaviour of TiC composite coatings

ABSTRACT Plasma transferred arc (PTA) welding methods were used to produce titanium carbide (TiC) composite coating layers on the surface of 38MnVS6 steel and subsequently deep cryogenic treatment (DCT) was applied to the PTA coating layers. The effects of the TiC powder, different energy inputs (100 and 120A), and DCT on the microstructure and tribological performance were investigated. The microstructure of the composite coatings consisted of cubic TiC, unmelted TiC, and iron matrix. The alloyed and cryogenic treated surfaces exhibited decreases in the coefficient of friction (COF) and wear rate. The average COF of the steel substrate was determined to be 0.373, but for the TiC composite coating layers it varied between 0.236 and 0.33. PTA coating and DCT processes improved the wear resistance 4.5 times compared to the substrate.

Mikrostrukutrelle Änderungen an SiC beschichteten und mit WIG Schweißtechnik erzeugten Metalloberflächen eines 45Mn5 Stahls

Kurzfassung In dieser Arbeit wurden mikrostrukturelle Änderungen von SiC-beschichteten Metalloberflächen eines 45Mn5-Stahls untersucht, die durch die Wolfram-Inertgas-Schweißtechnik (WIG) hergestellt wurden. In Abhängigkeit von Arbeitsparametern, z.B. von der Größe der Energieeinführung und von der benutzten Pulvermenge, erhält man verschiedene charakteristische Mikrostrukturen an beschichteten Oberflächen. Bei Arbeiten mit kleineren Pulvermengen erreicht man ein dendritisches Gefüge, während eine Erhöhung der Pulvermenge nach einer eutektischen Umwandlung zur Bildung der primären Dendriten mit intermetallischen Fe7C3−, FeSi2− und SiC-Verbindungsphasen führt. Durch Entstehung von Karbiden und sonstigen anderen Phasen wurden die Härtewerte der beschichteten Oberfläche merklich verändert. Die maximale Härte von 1058 HV wurde bei Oberflächen erhalten, die bei 30,1 kJ/cm Energieeinführung und 2,5 g Pulverzusatz erzeugt wurden, da unter diesen Arbeitsparametern SiC- und Fe7C3-Karbide entstanden.

Tribological and mechanical properties of deep cryogenically treated medium carbon micro alloy steel

In this study, the effects of deep cryogenic treatment (sub-zero treatments at -196 °C) on the microstructural, mechanical, and tribological behaviours of commercial Vanadium-Titanium micro-alloyed 38MnVS6+Ti steel was investigated. The samples were quenched (conventionally heat treated), deep cryogenically treated and then tempered at 250 °C for 1 h. Deep cryogenic treatments were applied for three different soaking times (namely 8 h, 12 h, and 24 h). The effects of deep cryogenic treatment on the specimens were evaluated in terms of impact toughness, hardness, wear resistance, and microstructure. The results indicated that the application of longer deep cryogenic treatment times significantly improved wear resistance, and improved the hardness slightly (1 to 3 HRC). However, deep cryogenic treatment also reduced the impact toughness compared to that of the conventionally heat treated sample, due to the precipitation of carbides and increasing hardness.