High Carbon Surface Research Articles

Microstructure and mechanical properties of a continuous carbon-gradient sheet steel

To take advantage of the high strength of high-carbon martensitic steel and simultaneously avoid insufficient plasticity, a novel continuous carbon-gradient sheet steel (CGSS) with a high-carbon surface and medium-carbon core was developed as a gradient material using surface carburizing and warm rolling. An exceptional strength–ductility combination was achieved. On the premise of carbides precipitation in high-carbon martensitic matrix, tempered CGSS at 200 °C exhibits excellent mechanical property with an ultimate tensile strength of 2440 MPa and a total elongation of 4.6%. Enlarged-strain-component in the tensile direction is the primary cause for higher plasticity in the high-carbon surface. Inhomogeneous fracture mode indicates the typical restraint of crack propagation in the core, suggesting greater toughness for the tempered CGSS.

ANALYSIS OF THE POSSIBILITY OF NON-DESTRUCTIVE TESTING OF THE CARBURIZING DEPTH OF 18KHGT STEEL USING POLE MAGNETIZATION

High-voltage transmission parts of energy-saturated machines are made of cemented steels subjected to chemical-thermal treatment. In low carbon steel, a strong high carbon surface layer is formed with a relatively soft and viscous core of the product. Non-destructive magnetic control of the depth of the hardened layer is based on the difference in the physical properties of the surface layer and the core of the product. The coercive force Hc has received the greatest application for quality control of surface hardening. One of the most common methods for controlling the properties of products made of ferromagnetic materials according to the results of the indirect determination of Hc is the “point pole” method. The modern implementation of the “point pole” method is implemented in the device “Magnetic Sorter MS-1”. The device measures the gradient of the normal component of the remanent magnetization field above the point of contact of the magnet pole with the surface of the product being monitored. The studis showed that there is a close correlation between the carburizing depth of the studied samples of 18KhGT steel and the readings of the MS-1 device. This is a prerequisite for the development of a non-destructive method for controlling the quality of cementation of gears of transmissions of mobile machines.

Contact angles of WC/WC grain boundaries with binder in cemented carbides with various carbon content

Contact angles of WC/WC grain boundaries (GBs) with the Co-based binder were measured by use of special model alloys with 10wt% Co, ultra-coarse grained microstructure and either a low or a high carbon content. The low-carbon sample contained significantly more low-angle WC/WC contacts with binder than the high-carbon sample. Therefore, the wettability of WC/WC GBs by the liquid Co-based binder is noticeably worse in the high-carbon sample than that in the low-carbon sample. The established worse wettability of WC/WC GBs by binders at high carbon content sheds light on the mechanism of the binder drift during sintering of functionally graded cemented carbides containing high-carbon surface layers.

Surface modifications of PADC polymeric material by ion beam bombardment for high technology applications

Surface modification of Poly (allyl diglycol carbonate) (PADC) is induced by 150 keV Ag ions of different fluences. The pristine as well as bombarded samples were investigated by UV–Vis spectroscopy, Fourier transform-infrared analysis (FTIR) and micro-hardness tester. The variations of wettability and surface free energy were determined by the contact angle measurements. The obtained results showed that ion beam bombardment induced increase in the absorption spectra of the UV–Vis with increase of ion fluence as well. The direct and indirect optical band gap decreased from 4.2 to 3.6 eV for pristine sample to 3.2 and 2.5 eV for those bombarded with Ag ion beam at the highest fluence, respectively. Changes in chemical properties were observed by Fourier transform infrared spectroscopy. Increase in the wettability, surface free energy and work of adhesion with increase the ion fluence were observed. Ion bombardment inducing increasing in a micro-hardness surface due to the high carbon surface concentration and cross-linking effects in the polymeric chains. The bombarded PADC surfaces may find special applications to the field of the micro-electronic devices and printing process.

Improving the coking resistance of Ni-based catalysts by promotion with subsurface boron

Carbon deposition on Ni catalysts was analyzed using first-principles density functional theory calculations. Based on the analysis, we propose boron as a promoter to improve the coking resistance of Ni-based catalysts. Three types of chemisorbed carbon were identified: on-surface carbon atoms, bulk carbon atoms, and extended graphene islands. Extended graphene islands were calculated to be the thermodynamically most stable form of deposited carbon. However, the formation of graphene islands requires high carbon surface coverage and might be kinetically limited at lower carbon coverage. Bulk carbon is found to be more stable than on-surface carbon and can form readily, even at low carbon coverage. Both bulk carbon and graphene islands might lead to catalyst deactivation and should be prevented. Addition of small amounts of boron to the Ni catalyst was found to inhibit the formation of bulk carbide and weaken the on-surface carbon binding energies, possibly slowing the formation of graphene islands. According to our calculations, boron prefers to adsorb in the octahedral sites just below the surface, rather than in the Ni bulk. A small amount of boron corresponding to a single monolayer was found to be sufficient to reduce coking of Ni-based catalysts.

Characterization of ultra-high-molecular-weight polyethylene (UHMWPE) modified by ion implantation

Surface modification of ultra high molecular weight polyethylene (UHMWPE) is induced by ion implantation of different ions at 300 keV energy. The aim of this work was the chemical, physical and mechanical characterization of the modified material in order to know deep inside about the effect of the ion beam upon the polymer. The irradiated surfaces are investigated by Raman spectroscopy, infrared absorption and micro-hardness analysis, scanning electron microscopy. Pin on disc measurements valuated the wear of the UHMWPE against a stainless steel probe; wear resistance increases of about 76% after the ion implantation. This result can be attributed to the ion bombardment inducing a micro-hardness increasing in the irradiated layers due to the high carbon surface concentration and cross-linking effects in the polymeric chains. The irradiated UHMWPE surfaces may find special applications to the field of the mobile prosthesis.

Characterization of ultra-high-molecular-weight polyethylene (UHMWPE) modified by ion implantation

Surface modification of ultra high molecular weight polyethylene (UHMWPE) is induced by ion implantation of different ions at 300 keV energy. The aim of this work was the chemical, physical and mechanical characterization of the modified material in order to know deep inside about the effect of the ion beam upon the polymer.The irradiated surfaces are investigated by Raman spectroscopy, infrared absorption and micro-hardness analysis, scanning electron microscopy. Pin on disc measurements valuated the wear of the UHMWPE against a stainless steel probe; wear resistance increases of about 76% after the ion implantation. This result can be attributed to the ion bombardment inducing a micro-hardness increasing in the irradiated layers due to the high carbon surface concentration and cross-linking effects in the polymeric chains. The irradiated UHMWPE surfaces may find special applications to the field of the mobile prosthesis.

Ion Implantation on Ultra High Molecular Weight Polyethylene (Uhmwpe) for Medical Prosthesis

In order to improve the wear resistance of ultra high molecular weight polyethylene (UHMWPE), a surface modification is induced by ion implantation of different ions at 300 keV energy with doses ranging between 1014 -1017 ions/cm2. Wear measurements, in terms of weight loss, are performed with a “pin on disc” friction machine; these tests measure the wear properly of the UHMWPE against a metallic probe before and after the ion implantation treatment. Results demonstrate that in the implanted samples the wear resistance increases by about 76% with respect to the non-irradiated samples. The irradiated polymeric layer was characterized with the mass quadrupole spectrometry, Raman spectroscopy, infrared absorption analysis, scanning electron microscopy, atomic force microscopy and calorimetric analysis. The results suggest that wear decrease effect can be attributed to the ion bombardment inducing a high carbon surface concentration and cross-linking effects in the irradiated polymeric layer. The irradiated UHMWPE surfaces find special applications in the field of the mobile prosthesis such as hip joints.

Obtaining wear-resistant high-carbon surface layers on steel and cast iron

Obtaining wear-resistant high-carbon surface layers on steel and cast iron

Activated carbon produced from an Illinois Basin coal

Activated carbons were produced from an Illinois Basin bituminous coal (IBC-106) by a three-step process: oxidation of the coal in air at 150–250 °C for 2–40 hours, devolatilization of these oxidized coals in nitrogen at 500–730 °C for 1 hour and activation (gasification) of the chars in 45% steam, 4% oxygen in nitrogen at 730–880 °C for 3.5–96 hours. Products were characterized in terms of CO 2 single-point BET surface area, helium and bulk densities, pore volume and toluene adsorption capacity. Seven of the nine carbons produced had surface areas exceeding 1000 m 2 g −1 (dry). It was confirmed that the application of oxidation pretreatment eliminates the caking of IBC-106, preserves the coal's microstructure, and leads to high carbon surface areas. In comparison with Darco coconut charcoal, a commercial activated carbon (Fisher Scientific) whose surface area was 547 m 2 g −1 (dry), the largest toluene adsorption capacity of activated carbons was 1.57 g g −1, four times more than that of Darco. Production costing analysis on a laboratory scale suggested that, in a single production run, the most cost-effective final product is not the activated carbon with maximum surface area but the carbon produced at the lowest cost for each square meter of pore surface area.