Soner Buytoz

Abrasive wear of Al2O3-reinforced aluminium-based MMCs

Abstract The effects of volume fraction, Al 2 O 3 particle size and effects of porosity in the composites on the abrasive wear resistance of compo-casting Al alloy MMCs have been studied for different abrasive conditions. It was seen that porosity in the composites is proportional to particle content. In addition, process variables like the stirring speed, and the position and diameter of the stirrer affect of the porosity content in a way similar to that observed for particle content. In addition, the abrasive wear rates of composites decreased more rapidly with increase in Al 2 O 3 volume fraction in tests performed over 80 grade SiC abrasive paper than in tests conducted over 220 grade SiC abrasive paper. Furthermore, the wear rates decreased with increase in Al 2 O 3 size for the composites containing the same amount of Al 2 O 3 . Hence, it is deduced that aluminium alloy composites reinforced with larger Al 2 O 3 particles are more effective against abrasive wear than those reinforced with smaller Al 2 O 3 particles. At the same time the results show that the beneficial effects of hard Al 2 O 3 particles on wear resistance far surpassed that of the sintered porosity in the compocasting metal-matrix composites (MMCs). Nevertheless, the fabrication of composites containing soft particles such as graphite favors a reduction in the friction coefficient. For this reason graphite and copper were used in the matrix in different amounts to detect their effect on wear resistance. Finally, it was seen that wear rate of the composites decreased considerably with graphite additions.

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.

Wear Properties of Fe-Cr-C and B4C Powder Coating on AISI 316 Stainless Steel Analyzed by the Taguchi Method

Abstract In this study, the plasma arc welded cladding of FeCrC and B4C powder mixtures alloyed with 70 wt.- % Cr on the surface of AISI 316 stainless steel was investigated. Application of the Taguchi method revealed respective effects on the abrasive wear resistance of the cladding layer on the stainless steel. The abrasive wear behaviour of the AISI 316 stainless steel surfaces coated with Fe-Cr-C and with 10 wt.-%, 15 wt.-%, 20 wt.-%, and 25 wt.-% B4C was investigated by using four loads and four distances for the 220 mesh SiC abrasive. Results were analyzed by variance analysis using ANOVA, and effects of parameters on the wear rate were determined as percentage rate. Furthermore, the error ratio was statistically evaluated. The experimental results were analyzed by the respective analysis of means and variance which is discussed in detail.

The corrosion characterization of a ferritic stainless steel with Mo addition in H2SO4 and HCI acid solutions

The corrosion behavior of ferritic stainless steel containing 1 wt, % Mo was investigated using an AC impedance technique and the mass loss method. The alloys were produced by casting and forging. They were classified into three groups: unhomogenized, homogenized for 30 minutes and homogenized for 180 minutes. Mass loss tests were carried out on samples homogenized for 180 minutes. The corrosion tests were performed in 0.1 M H2SO4 and 0.3 M HCl acid solutions. SEM investigations were performed on the surface of samples exposed to corrosion for 30 and 360 minutes. The results were compared with results obtained from experiments performed on unalloyed ferritic stainless steel. Molybdenum (Mo) and homogenization heat treatment were found to have a beneficial effect on corrosion behavior of ferritic stainless steel in these solutions.

Influence of thermal properties on microstructure and adhesive wear behaviour of Al/Al2O3 MMCs

Abstract Al alloy and Al/Al2O3 metal matrix composites (MMCs) were fabricated by stir casting. Effect of the thermal properties on wear properties and stir casting parameters on the dry sliding wear resistance of this alloy and Al/Al2O3 MMCs were investigated under 50–350 N loads. The temperature was applied at ambient and elevated intervals (300–475 K), which was controlled by an external heat source. The dry sliding wear tests were performed to investigate the wear behaviour of Al alloy and Al/Al2O3 MMCs against a steel counterface (DIN 5401) in a block on ring apparatus. The Al/Al2O3 MMCs were prepared by the addition of 5, 10 and 15 vol.-%Al2O3 particulates, and the size of particulates was taken as 16 μm. The wear tests were carried out in an incremental manner, i.e.300 m per increment and 3000 m in total. The wear test results were used for investigation of the relation between weight loss, microstructure, surface hardness, friction coefficient, particulate percentage and thermal conductivity of Al/Al2O3 MMCs. Finally, it was observed that Al2O3(p) reinforcement is beneficial in increasing the wear resistance of Al/Al2O3 MMCs. Furthermore, Al2O3 particulates in MMCs tend to reduce the extent of plastic deformation in the subsurface region of the matrix, therefore delaying the nucleation and propagation of subsurface microcracks. On the other hand, it can be seen that the increase in Al2O3 particulates decreased both thermal conductivity and friction coefficient, hence increased the transition load and transition temperature for mild to severe wear during dry sliding wear test.

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.

Microstructure and Microhardness Characterization of Cr 3 C 2 -SiC Coatings Produced by the Plasma Transferred Arc Method

Abstract The purpose of this work was to investigate the coatings made of Cr3 C2 and SiC powder manufactured on AISI 304 stainless steel applied by the plasma transferred arc (PTA) welding process. SiC content in the produced coated layer was varied between 0–100 wt.% and the effect of SiC concentration on the microstructure and hardness of the coating was measured experimentally. SEM analyses revealed that the composite coatings had a homogeneous, nonporous, and crack-free microstructure. Dendrites and interdendrite eutectics formed on the coating layer, subject to the temperature gradient and the solidification ratio. There was a significant increase in the hardness of coating layers with the effect of the γ -(Fe,Ni), Cr7 C3, Cr23 C6, Fe5 C2, Cr3 Si, CrSi2, Fe>0.64 Ni0.36, CFe15.1, C-(Fe,Cr)-Si phases formed in the microstructure. In comparison to the substrate, the microhardness of the coatings produced by PTA were 2.5–3.5 times harder.

Effects of FeCrC and FeSiCrC particles on wear behaviour of aluminium metal matrix composite

Abstract The tribological behaviour of Al–FeCrC(p) and Al–FeSiCrC(p) composites produced by the stir cast method was studied under dry sliding conditions against AISI 4340 steel, using a pin on ring aparatus. The effect of the composites on the wear behaviour of primary M7C3 carbides and secondary Al3Fe and α-AlFeSi phases in all composites was investigated. The hardness values were changed between 68 and 120 HB for composite materials. The peak hardness was measured to be 120 HB for Al–15FeSiCrC(p) (vol.-%) composite. The hardness values of other composites were also increased when the particle content was increased. Worn test specimens were examined by scanning electron microscopy, and wear mechanisms were determined. The particulates are distributed uniformly within the aluminium alloy matrix as well as the improved wear characteristics when compared with the base alloy. Increasing applied load increased the wear rate. However, the wear rate was decreased as a function of the sliding distance.

Microstructural Characteristic of Co-Cr-Mo Powder Alloy Coating on Stainless Steel by Plasma Transferred Arc Weld Surfacing

Abstract In this study, Co-Cr-Mo powder was coated on the surface of AISI 304 stainless steel by the plasma transfer arc (PTA) process at 80, 90 and 100 A current values and argon gas was used for both plasma and protective. Deposition layers were examined with optical microscopy, SEM, EDX, XRD analysis and microhardness test. The thickness of the coating increased with current density. No cracks or pores were detected in the interface and coating layer. Higher current levels resulted in higher dilution levels and also in melting/burning of the substrate.

Microstructural and abrasive wear properties of tungsten inert gas deposited FeCrC and WC coatings on AISI 4340 steel

Kurzfassung Zur Untersuchung kamen das Verschleisverhalten von Metall-Matrixverbundbeschichtungen aus hochchromhaltigem Ferrochrom-Kohlenstoff, Wolframkarbid und hochchromhaltigem Ferrochrom/Kohlenstoffkarbid/Wolframkarbid. Die Verschleistests der Beschichtungen wurden mit einer Pin-on-Disc-Apparatur mit Lasten von 10, 20 und 30 N durchgefuhrt. Die Auswirkungen der Last auf den Gewichtsverlust der Verbundschichten wurden bestimmt. Die Variationen der Werte des Gewichtsverlusts zeigten einen leichten Anstieg des Gewichtsverlusts mit Ausnahme bei einer Last von 20 N und einer Gesamtgleitlange von 60 m. Eine Zunahme mit der Last erhohte die Werte des Gewichtsverlusts der Proben. Anderungen der Mikroharte und des Verschleisabtrages stimmen gut mit Veranderungen im Gewichtsverlust uberein. Das Verschleisverhalten des Beschichtungsmaterials ist abhangig vom Gefuge der Matrix und Merkmalen der verteilten Karbide wie Form, Anteil, Grose und Verteilung.