جستجوی مقالات مرتبط با کلیدواژه « diamond-like carbon » در نشریات گروه « فنی و مهندسی »

Diamond-like carbon (DLC) coatings have become highly popular in automotive engine components, particularly piston parts, owing to their unique properties. The main goal of these coatings is to enhance adhesion to metal surfaces, increasing wear resistance and providing tribological lubrication to prevent friction-related wear. Various methods, including Plasma-Assisted Chemical Vapor Deposition (PACVD), are employed for precise control over DLC coating thickness, leading to improved component lifespan and performance. Recent studies have explored different aspects of this technology, examining its impact on reducing wear, enhancing engine efficiency, and addressing triple-fretting corrosion issues on high-strength steel. For instance, layers like Si, SiH, Cr, and CrN have been identified to create a smooth surface, improving DLC coating adhesion. Conversely, layers such as Ti and TiN may negatively affect adhesion, hindering effective interactions between DLC coatings and steel. Additionally, the incorporation of non-metallic elements like Si, N, and F into DLC coatings can enhance their performance against wear, ultimately increasing component lifespan.

In this study, the effects of F-doped diamond-like carbon (F-DLC) thin films on corrosion resistance of the cobalt-chromiummolybdenum (CoCrMo) alloy substrate were investigated. For this purpose, deposition of F-DLC thin film on CoCrMo substrates was carried out through radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) method. Methane, argon and CF4 gases were used to deposition of F-DLC thin film. TiN intermediate layer was used to improve the adhesion of F-DLC thin film on CoCrMo substrate. Corrosion behavior of the samples have been determined using electrochemical impedance and polarization tests. Electrochemical measurements indicated that the corrosion resistance of CoCrMo substrates increases to a great extent by deposition of F-DLC thin film, so that the corrosion potential and corrosion current decreased from -0.396 volt to -0.057volt and from 5.55×10-6 to 1.288×10-7 µA, respectively. Raman spectroscopy, as a nondestructive method to characterize carbon-based materials, was used for the structural characterization of DLC and F-DLC films. The results demonstrated that higher concentration of sp2 bonding and more graphitic structure in the F-DLC films, which could lead to lower intrinsic stress in these films, compared to those of the DLC coatings.

The composition of the coating used In the piston ring has a great effect on friction and wear in combustion engines. In the present study, the wear behavior of three samples of TU3 engine ring with hard chromium, chromium nitride, and diamond-like carbon coatings were studied and compared. Various coating properties including chemical composition, microstructure, thickness, roughness, and hardness were studied. Also, the microstructure and wear mechanism was studied using a scanning electron microscope (SEM) and energy dispersive analysis (EDX). A reciprocating wear test device was used to check the wear behavior of the piston rings. In the end, an attempt was made to investigate the relationship between properties and tribological behavior created in piston rings. The high hardness and the presence of graphite as a solid lubricant were among the most important factors for the appropriate wear behavior of the piston ring with a diamond-like carbon coating. Due to the lack of complexity and high hardness, the piston ring with hard chromium coating has a sticky wear mechanism and does not show proper wear behavior. The worst wear behavior was observed in the piston ring sample with chromium coating. Low adhesion to the substrate, low hardness, high roughness and thickness, and single layer can be considered as the most important factors of inappropriate wear behavior of this sample. Also, the results showed that the wear resistance of diamond-like carbon coating is almost four times that of chromium nitride coating and six times that of hard chromium.

Carbon ion energy is a key factor in determining the amount of sp3 bonds in the structure of the amorphous carbon film and its like-diamond nature. In this study, the structural evolution of diamond-like carbon coating based on the mechanism of sp3 bond formation of amorphous carbon under the influence of the ion beam energy in the radio frequency ion-beam deposition process were investigated. For this purpose, the parameter of ion beam energy was 200, 300, and 400 eV ​​ for the deposition of DLC coatings. Raman and X-ray spectroscopy (XPS) analyzes were used to evaluate the structure and chemical composition of the coatings. Also, in order to determine the effect of ion beam energy on the surface roughness and thickness of the applied coatings, atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) were used. Hardness and elastic modulus were measured by nanohardness test. According to the results of Raman analysis, the lowest value of ID/IG ratio was obtained in ion beam energy of 300 eV, which was equal to 0.66. The results of XPS analysis showed the lowest amount of sp2 bonds in the diamond-like carbon film at ion beam energy of 300 eV. Also, results of AFM analysis showed at ion beam energy of 300 eV, the surface roughness of diamond-like carbon coating has the lowest value. Due to the highest amount of sp3 bonds in the ion beam energy of 300 eV, the diamond-like carbon coating had the highest hardness and was equal to 10.6 GPa.

The substrate temperature plays an important role in the mobility of carbon species as well as the formation and growth mechanism of the amorphous carbon layers with diamond-like characteristics. The amorphous carbon structure can be transformed into the diamond- and graphite-like structure under the effect of substrate temperature. Given that, this study aimed to investigate the structural evolution of the diamond-like carbon coating followed by changing the substrate temperature through the radio frequency direct ion beam deposition. In this regard, the substrate temperature values were obtained as 80, 110, and 140 °C for the deposition of DLC coatings. Raman and X-Ray Spectroscopy (XPS) analyzes were done to evaluate the structure and chemical composition of the coatings. To further investigate the thickness and roughness of the applied coatings, Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) were used. According to the results, the lowest roughness value of the diamond-like carbon coating surface was obtained at the substrate temperature of 110 °C. In addition, the lowest value of ID/IG and the highest amount of sp3 bonding were obtained at the same substrate temperature.

This study, investigates the effect of bias voltage on structural changes of diamond-like carbon thin film created by ion beam deposition is investigated. For this purpose, the bias voltage in the values of 0 V, -50 V, -100 V and -150 V on the AA5083 aluminum alloy was considered. Raman spectroscopy was used to evaluate structural. Influence of the bias voltage on the thickness and roughness of coatings by atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) were investigates. Hardness and elastic modulus were measured by nanoindentation test. The results of Raman analysis showed the highest amount of sp3 bonds in the diamond-like carbon thin film at bias voltage of -50 Vs. results of AFM showed the lowest of surface roughness (10 nm) at bias voltage of -50 Vs. The hardness of diamond-like carbon thin film was 14.1 GPa at the bias voltage of -50 Vs.

In this work, diamond-like carbon (DLC) films were deposited on silicon substrate by an ion beam method (IBM ) using propane (C3H8) and argon (Ar) gases. Then, thermal annealing effects (from 200ºC to 500ºC) on the chemical and optical properties of the diamond-like carbon thin films were investigated. Structures, morphology, chemical and optical properties of the films were investigated by Raman spectroscopy, field emission scanning electron microscopy (FESEM ) and fourier transform infrared (FTIR) spectrometry methods. The Raman results proved that increasing of the annealing temperature (Ta) cause to the conversion of chain links to aromatic rings. Based on the FESEM results, the micro-cracks were formed in the film at 200 ºC. Altogether the results showed that decomposition of the DLC films begins at the annealing temperature above 300 °C. As Ta was further increased to 500 °C, the main part of the film was oxidized. Also FTIR analysis indicated that by increasing Ta, the transmission of the DLC film was decreased in the wavelength range of 3-5 μm.