Browsing by Author "Türkmen, I"
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item Investigation of tribological behaviour and diffusion model of Fe2B layer formed by Pack-boriding on SAE 1020 steelTürkmen, I; Yalamaç, E; Keddam, MIn this study, a substitute boriding poWder including boric acid as boron source was Prepired and employed for boronizing of SAE 1020 steel. The boronizing processes were performed at 850, 900 and 950 degrees C for 4, 8 and 12 h. The formed boride layers were identified by varied experimental methods such as optical microscope, SEM and WDS analysis. As an outcome of the analyses, the boride layer containing only. Fe2B phase with saw-tooth morphology was specified on surface of the samples. A diffusion model was proposed to estimate the coefficients of boron diffusion in the Fe2B layers. The value of boron activation energy for SAE 1020 steel was calculated as 183.14 kJ/mol and the result was contrasted with literature data. As a result of the rnicrohardness measure- . ments, the average hardness value of Fe2B layer was about between 1200 and 2000 HV0.1. The average hardness values of the transition zone and matrix zone were determined to be approximately 160 HV0.1 and 151 HV0.(1), respectively. This study mainly concentrates on the tribological properties of borided SAE 1020 steel with using alternative boriding powder. Coefficient of friction graph was drawn for each sample and the wear rates were calculated. It was specified that specific wear rate of borided samples was roughly 47 times lower than that of unborided samples.Item Cold metal transfer welding of AA1050 aluminum thin sheetsIrizalp, AO; Durmus, H; Yüksel, N; Türkmen, IThis study was aimed to investigate the welding parameters on mechanical behavior of 2 mm thick AA1050 sheet materials joined by cold metal transfer (CMT) method. Macro structural examination showed that decreasing heat input decreased the pore size in the weld metal. Tensile test was applied and failure occurred in heat affected zone of aluminum sheet metal. Maximum tensile strength was found in the sample with minimum heat input. Heat affected zone was observed explicitly in the sample produced with the maximum heat input. Decreasing joint gap affected the bending strength positively. Bending strength was found superior with maximum bonding line length.Item Comparative study on the thermal and tribological properties of PA12 and PA11 for coating applicationsBasaran, S; Türkmen, I; Yagci, T; Kanbur, K; Bastürk, SBIn this study, the performance and potential applicability of polyamide-12 (PA12) as an alternative to polyamide-11 (PA11), which is currently used in the coating processes of sliding tools present in cardan shafts, was investigated. The advantages of PA12 powder instead of PA11 in cardan shafts' coating include ease of supply and cost-effectiveness, while still achieving similar performance. Therefore, PA12 is a more economical choice for coating applications. The PA11 and PA12 neat polymers were characterized via differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Based on the analyses, PA12 demonstrated substantial advantages over PA11. It showed a 16 degrees C improvement in decomposition temperature and a 50% increase in crystallinity, enhancing stability under operational conditions, whereas PA11 exhibited approximately 6-7% higher values in crystallization and melting temperatures. The wettability behavior of the steel substrates coated with those polyamides was measured via contact angle analysis. Wear properties and morphologies of coatings were examined using a ball-on disc test and scanning electron microscopy, respectively and comparatively. Furthermore, PA12 typically displays 30% lower wear rates and similar deformation patterns in tests, thereby presenting itself as a cost-effective and widely accessible option for coating applications in comparison to PA11.Item Boronizing of Monel K500 alloy: Microstructural characterization and modeling of boron diffusionTürkmen, I; Keddam, MIn this study, the thermochemical treatments were carried out using the powder-pack boronizing method at temperatures ranging from 1123 K to 1223 K for durations of 2 to 6 h, with the aim of improving the surface properties of Monel K500 alloy. Microstructural investigation of the boride layers, conducted using optical microscopy (OM) and scanning electron microscopy (SEM), revealed a needle-like layer structure with high porosity homogeneously distributed on the surface. The results of XRD analysis showed that the boride layer contained different nickel borides (Ni2B, Ni3B, Ni4B3 and NiB12), iron borides (Fe2B and Fe3B) and complex borides (Fe4.5Ni18.5B6 and Fe3Ni3B). The presence and amount of elements in the boride layer were determined by EDS analysis. This study focused mainly on diffusion kinetics studies of boronized Monel K500 alloy. Growth kinetics of the boride layer were investigated using three different approaches such as parabolic growth model, regression model and mean diffusion coefficient (MDC) model. Boron activation energy values were calculated and found to be quite similar, at 266.14 kJ mol-1 and 266.17 kJ mol-1 using the MDC model and parabolic growth model, respectively. These values were compared with similar results reported in the literature.Item Growth of the Fe2B layer on SAE 1020 steel employed a boron source of H3BO3 during the powder-pack boriding methodTürkmen, I; Yalamac, EIn this study, an alternative powder-pack boriding mixture containing H3BO3 as boron source was prepared and used for boriding of SAE 1020 steel. The boriding treatment was carried out in the temperature range of 850-950 degrees C for a treatment time ranging from 4 to 12 h. The generated boride layers were characterized by different experimental techniques such as optical microscope, SEM, XRD analysis and the Daimler-Benz Rockwell C indentation test. The powder-pack boriding mixture was analyzed by TGA and DTA methods and the possible chemical reactions that may be occurred during boriding were investigated. Furthermore, the growth kinetics of the boride layer forming on SAE 1020 steel substrates was investigated. A regression model based on a full factorial design was used to estimate the boride layers' thicknesses as a function of the boriding parameters. A single phase boride layer with saw-tooth morphology was formed on the steel samples. The value of boron activation energy for SAE 1020 steel was estimated as 183.15 kJ/mol. The comparisons were made between the empirical values of the boride layers' thicknesses with estimated ones. The contour diagrams were plotted for estimating the thickness of boride layer as a function of the temperature and time. (C) 2018 Elsevier B.V. All rights reserved.Item Failure analysis of copper pipes used in the heat exchangers in fan coil unitsSargin, F; Kanbur, K; Türkmen, IHeat exchangers (HE) consist of copper and steel pipes and are used for heating and cooling the ambient air. One of the main problems seen in HE is the leakage on copper pipes. In this study, failed and properly working copper pipe samples used for different durations were examined in detail. The microstructural analyses were performed using optical microscopy (OM) and scanning electron microscopy (SEM) to detect corrosion occurrences on copper pipe surfaces. In addition, corrosion products of the samples were de-fined by X-Ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses. The formation of interconnected tunnels in cross section of the failed copper pipe sample that were in microscopic dimensions and corrosion products were observed. Consequently, all the analyses result that were obtained from the samples pointed out a corrosion mechanism known as ant-nest corrosion. It was concluded that the main reason of corrosion was related to ethylene glycol type additives which were used in HE along with mains water.Item Effect of Alternative Boronizing Mixtures on Boride Layer and Tribological Behaviour of Boronized SAE 1020 SteelTürkmen, I; Yalamaç, EIn this study, SAE 1020 steel samples were boronized at 850 degrees C for 4 h with different boronizing mixtures by powder-pack boronizing method. H3BO3 or Na2B8O13 was used as the boron source, KBF4 or NaBF4 was used as the activator and SiC was used as the diluent. Thus, 4 different boronizing mixtures (M1-M4) were prepared. Thickness, morphology and phase structure of the formed boride layers were studied by X-ray diffraction and microstructural analyzes. The single phase (Fe2B) boride layer with saw-tooth morphology was formed on surface of the samples. The thickest boride layers were obtained by using M1 and M2 boronizing mixtures. Microhardness measurements were performed to determine hardness of the 3 zones (core, transition zone and boride layer). The means of boride layer hardness of the samples were compared according to 95% Confidence Intervals analysis. It was determined that the average hardness value of the boride layers was about 1475 HV. Wear tests were fulfilled by ball on disc type wear test method under dry sliding condition and at 25 degrees C. According to the friction coefficient and specific wear rate values of boronized samples, it was identified that the sample S-M4 boronized with M4 boronizing mixture has the lowest wear rate (1.64 mm(3)/N.m) and friction coefficient value (0.63). GraphicItem Characterization and Kinetic Analysis of Iron Boride Layer Formed on the GGG 70 Ductile Cast IronYalamaç, E; Türkmen, I; Firtina, ÖAn alternative powder-pack boriding powder mixture containing H3BO3 as boron source and commercial boriding powder containing B4C as boronizing agent were used for boriding of GGG 70 type ductile iron. As a result of XRD analysis, while only Fe2B phase was detected on the samples boronized with alternative boriding mixture, besides Fe2B phase, small amount of FeB phase was also determined on the samples boronized with commercial powder. The growth kinetics of the boride layer forming on ductile iron was investigated and compared with literature studies. The value of boron activation energy for ductile iron was calculated as 184.67 kJ/mol. An empirical equation and a regression model were derived to estimate the thicknesses of boride layer as a function of the boriding parameters. The comparisons were made between the experimental boride layer thicknesses with estimated ones and the results were consistent with 99% accuracy.Item Mechanical Properties of Dissimilar and Similar Cold Metal Transfer Welded Galvanized Steel 1314 and Aluminum AA1050Irizalp, AO; Durmus, H; Yüksel, N; Türkmen, I; Uzun, OThis study aims to investigate the weldability of 1050 aluminum alloy (AA1050) and galvanized 1314 steel by the cold metal transfer (CMT) procedur, comparing it with respective welding of similar aluminum sheets. Mechanical properties of welded specimens were determined by tensile testing and hardness measurements. The study was completed by microstructural analysis. The results showed that CMT welding can be applied successfully to join aluminum and steel.Item Microstructural and mechanical characterization of powder-pack boronized Incoloy A286 superalloyTürkmen, I; Korkmaz, AIn this study, Incoloy A286 superalloy were boronized successfully by powder-pack boronizing process at 850 degrees C, 900 degrees C and 950 degrees C for 4 h by using a boronizing powder mixture containing H3BO3 as boron source. The thickness and morphology of the boride layer was identified by microstructural examinations. The boride layer with complex, compact and smooth morphology was formed on the surface of the samples. As a result of XRD analyses, it was determined that the compact boride layer was formed many phases such as FeB, Fe2B, Fe3B, CrB and Ni4B3 etc. It was specified that the average hardness value of the boride layer was approximately between 2400 and 3000 HV by microhardness tests. Also the graphs of friction coefficient and values of the specific wear rate were obtained by performing ball on disk wear tests. It was identified that the specific wear rate of boronized samples was approximately 9.5 times lower than that of unboronized samples.Item Enhancing surface properties of AISI P20+Ni mold steel via boronizing: Evaluation of mechanical, tribological, and corrosion performanceTürkmen, IIncreasing the mold service life via improving the surface properties of AISI P20 + Ni steel, which is frequently used in the production of plastic injection molds, through the boronizing process may have significant implications for the industrial sector in terms of enhancing production efficiency. In this study, AISI P20 + Ni mold steel was borided at various temperatures (850, 900, and 950 degrees C) and durations (3, 6, and 9 h) employing a non-commercial boriding admixture containing H3BO3 via powder-pack boronizing method. The layer's morphology and thickness were assessed using optical microscopy and scanning electron microscopy. Boride layers exhibiting a saw-tooth morphology, uniformly distributed across the substrate surface, were identified. X-ray diffraction and energy-dispersive X-ray analysis were employed to analyze the phase constituents and chemical composition of the boride layer. As a result of these analyses, the presence of a single-phase (Fe2B) boride layer was detected. Microhardness tests indicated that the boronized sample surface had an average hardness of around 1900 HV. Wear tests were conducted utilizing the ball-on-disk method at ambient (room) temperature under dry sliding conditions, revealing an approximately 23-fold increase in the wear resistance of boronized materials. Contact angle analysis was employed to evaluate the wettability behavior of the substrate and borided samples. Corrosion tests were conducted using the linear polarization resistance method in a 3.5 wt% NaCl solution, and it was observed that the corrosion rate of the sample boronized at 900 degrees C for 6 h was approximately six times lower than that of the substrate material. Indentation fracture (IF) toughness tests of the boride layers were performed using a Vickers microindentation. The IF toughness value of boride layers decreased with increasing process duration and temperature.Item Characteristics of boronized Ti6Al4V alloy using boric acid based boronizing mixtureTürkmen, I; Kanbur, K; Sargin, FBoronizing processes of Ti alloys are generally performed in atmosphere-controlled furnaces. In this study, it is aimed to carry out boronizing process under atmospheric conditions by using an alternative boronizing mixture containing boric acid and to better the surface characteristics of Ti6Al4V alloy by boronizing. The efficiency of the boronizing mixture was evaluated by performing boronizing at different process temperatures (900-1100 degrees C) and durations (12 and 20 h). Microstructural (OM, SEM) and chemical (XRD, EDS, XPS) analyzes were performed to characterize the boride layers formed on the surfaces of the boronized samples. As a consequence of these analyzes, it was found out that a two-phase boride layer (TiB2 + TiB) was obtained in the samples. In addition, in vitro tests were done for specifying the bioactivity of boronized samples. In order to determine the effect of boronizing on the corrosion resistance of Ti6Al4V alloy, corrosion tests were performed by the Tafel extrapolation method. The adhesion behavior of the boride layers was determined by the Daimler-Benz Rockwell C indentation test. As a result, boronizing studies have been performed successfully without atmosphericcontrolled conditions and it has been defined that surface characteristics of the Ti6Al4V alloy have bettered through the boride layers formed on the alloy surface.