scholarly journals Influence of pulse-plasma modification of VK10KS solid alloy surface by titanium and boron on its structure and properties

2020 ◽  
Vol 63 (5) ◽  
pp. 351-356
Author(s):  
T. N. Oskolkova ◽  
A. S. Simachev
Keyword(s):  
Friction Coefficient ◽  
Tungsten Carbide ◽  
Plasma Modification ◽  
Pulse Plasma ◽  
Solid Alloy ◽  
Deformation Bands ◽  
Near Surface ◽  
Scanning Transmission ◽  
Electroexplosive Alloying ◽  
Slip Planes

Modification of the surface of VK10KS solid alloy with titanium alongside with boron by the method of pulse-plasma exposure (electro-explosive alloying) is considered. In this case, a superhard (27,500 MPa nanohardness) layer is formed with a thickness of 2.0 – 2.5 μm and a low (μ = 0.10) friction coefficient compared to the friction coefficient of a hard alloy in the sintered state (μ = 0.41). This layer consists of finely dispersed high-hard phases TiB2, (Ti, W)C, W2C (according to scanning, transmission electron microscopy and X-ray phase analysis). Below is a hardened (with a nanohardness of 17,000 MPa) surface layer (heat affected zone) 10 – 15 μm thick, identified by W2C and WC carbides and alloyed with a cobalt binder. This layer smoothly passes into the base. By profilometric studies it was established that after electroexplosive alloying with titanium and boron, the roughness increases (Ra = 2.00 μm) compared to the initial one (Ra = 1.32 μm), but remains within the specifications (Ra = 2.50 μm). The authors have revealed changes that occur in the surface carbide and near-surface cobalt phases during electroexplosive alloying. In the carbide phase, accumulations of dislocations were indicated. In the cobalt binder, deformation bands (slip bands), single dislocations, and also finely dispersed tungsten carbide precipitates were found. This change can be explained by stabilization of the cubic modification of cobalt, the crystal lattice of which has a large number of slip planes during deformation and a greater ability to harden compared to the hexagonal modification of cobalt. Additional alloying with a cobalt binder will positively affect the operational stability of tungsten carbide alloys as a whole due to their stabilization.

scholarly journals Influence of pulse-plasma modification with titanium and silicon carbide of the surface of hard VK10KS alloy on its structure and properties

2021 ◽  
Vol 63 (11-12) ◽  
pp. 922-928
Author(s):  
T. N. Oskolkova ◽  
A. S. Simachev ◽  
S. I. Yares’ko
Keyword(s):  
Electron Microscopy ◽  
Silicon Carbide ◽  
Plasma Treatment ◽  
Hard Alloy ◽  
Plasma Modification ◽  
Pulse Plasma ◽  
Carbide Powder ◽  
Hard Alloys ◽  
Tungsten Carbides ◽  
Near Surface

Electro-explosive alloying as a method of pulse-plasma treatment consists in accumulation of energy by a battery of pulsed capacitors and its subsequent discharge for 100 μs through a conductor in form of titanium foil with silicon carbide powder, while conductor is under explosive destruction. Method of electro-explosive alloying of tungsten-cobalt hard alloy includes melting of surface and its saturation with explosion products, followed by self-hardening by removing heat deep into the material and environment. On the surface of VK10KS hard alloy, the coating was obtained with thickness of up to 15 – 20 microns with nanohardness of 26,000 MPa. Using X-ray phase analysis and scanning electron microscopy, it has been established that new phases of TiC, W2C, (W, Ti)C1 – x , WSi2 with high hardness were formed in the surface layer. As a result, friction coefficient decreased to 0.18 compared to the initial 0.41. Investigations with transmission electron microscopy have revealed changes during electro-explosive alloying that occur in surface carbide and near-surface cobalt phases. Dislocations accumulations were found in the carbide phase. In cobalt binder, deformation bands (slip bands), single dislocations, and finely dispersed precipitates of tungsten carbides were revealed. This change can be explained by stabilization of cubic modification of cobalt, crystal lattice of which has a large number of slip planes upon deformation and greater ability to harden in comparison with hexagonal modification of cobalt. Additional alloying with cobalt binder in heat affected zone after pulse-plasma treatment have a positive effect on the service life of tungsten-cobalt hard alloys as a whole due to their stabilization.

Effect of Microstructure on Mechanical Properties and Wear Characteristics of Cemented Tungsten Carbides

2009 ◽  
Vol 76-78 ◽  
pp. 609-612 ◽  
Author(s):  
H.Q. Sun ◽  
Rudy Irwan ◽  
Han Huang ◽  
Gwidon W. Stachowiak
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Friction Coefficient ◽  
Tungsten Carbide ◽  
Removal Rate ◽  
Tungsten Carbides ◽  
Removal Rates ◽  
Wear Characteristics ◽  
Effect Of Microstructure

The effect of microstructure of cemented tungsten carbide materials on their mechanical properties and wear characteristics was investigated using nanoindentation and nanoscratch methods. The results indicated that the variation in grain size insignificantly affected the hardness, elastic modulus and friction coefficient of the work materials, but considerably influenced their removal rates. The carbide with coarser grains exhibited a much higher removal rate was obtained during scratching.

Influences of Cobalt Content on the Physical and Tribological Properties of Cemented Tungsten Carbide Used in Sheet Metal Forming Application

2014 ◽  
Vol 966-967 ◽  
pp. 80-86
Author(s):  
Varunee Premanond ◽  
Onnjira Diewwanit
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Friction Coefficient ◽  
Tungsten Carbide ◽  
Cobalt Content ◽  
Steel Ball ◽  
Cemented Carbide ◽  
Average Grain Size ◽  
Stainless Steel Ball ◽  
Cemented Tungsten Carbide

The objective of this work is to investigate the tribological behavior between WC-Co cemented carbide and austenitic stainless steel under repeated rotation sliding. Influences of cobalt content of commercial grade cemented tungsten carbide on friction coefficient and material transfer phenomena have been explored. Three grades of commercial WC-Co cemented carbide with similar medium WC grain size were employed; WC-12Co, WC-14Co and WC-19Co. The average grain size were ranges between 0.85-1.1 μm and the hardness of about 86-88 HRA have been given by the material maker. The composition analysis and the average grain size of tungsten carbide have been rechecked. Furthermore, the carbide grain size distribution was recorded and the fracture toughness was calculated for each WC-Co grade. The experiments were carried out using ball on disk test. The ball was made from SUS304 grade and the disk was fabricated by 3 grades of WC-Co cemented carbide. The friction coefficient was measured under dry sliding. The characteristics of contact surfaces were explored on the ball as well as on the disk after tests to reveal the presence of a metallic transfer on the WC-Co cemented carbide disk and the wear scar on the ball. The measurement results of wear volume on the stainless steel ball disclosed that maximum wear rate was found from the stainless steel ball rub against WC-19Co tool material.

Effect of Titanium Implantation on the Mechanical Properties of Silicon Nitride

1994 ◽  
Vol 354 ◽  
Author(s):  
T. Fujihana ◽  
O. Nishimura ◽  
K. Yabe ◽  
H. Hayashi ◽  
M. Iwaki
Keyword(s):  
Mechanical Properties ◽  
Friction Coefficient ◽  
Room Temperature ◽  
Surface Hardness ◽  
Atomic Fraction ◽  
Metallic State ◽  
Wear Properties ◽  
Surface Layers ◽  
Near Surface ◽  
Projected Range

AbstractA study has been made of the chemical composition and mechanical properties of Ti+-implanted Si3N4 surface layers. Implantation of 48Ti+ was performed with doses ranging from 10 to 1017 ions cm”2 at an energy of 150 keV, and at nearly room temperature. XPS was used to analyze the depth dependence of atomic fraction and chemical bonding states of Ti+-implanted layers. The near-surface hardness was measured by a Vickers hardness tester. The friction and wear properties were measured under unlubricated conditions at room temperature using a pin on disk-plane and a block on wheel-periphery configurations, in which the pin and wheel used were AISI1045 and ASTM Wl-9, respectively. Implanted Ti-atoms formed a gaussian distribution predicted by the range theory. At the average projected range, most of Ti-atoms existed as a metallic state and TiN bonding was also formed. Oxygen and carbon were found near the surface layers. In addition to the surface peak, O-atoms accumulated in front of the average projected range of Ti. Such O-atoms formed bonds of Si-oxides and Ti-oxides. Carbon existed as a graphitic state. With increasing a Ti dose, the near-surface hardness decreased, and the wear rate increased at the running-in stage having the high friction coefficient. The steady wear attributed to the stable friction coefficient appeared after the running-in stage, although such a stable stage was not observed for unimplanted Si3N4. The mechanism for the change in mechanical properties of Si3N4 induced by Ti+-implantation will be discussed in relation to XPS characteristics.

Investigation of the Effect of Tungsten Carbide (WC) Nanopowder on Iron-Based Powder Structural Materials

2021 ◽  
Vol 316 ◽  
pp. 455-460
Author(s):  
V.M. Gavrish ◽  
T.V. Chayka ◽  
G.A. Baranov
Keyword(s):  
Mechanical Properties ◽  
Tungsten Carbide ◽  
Particle Morphology ◽  
Single Stage ◽  
Powder Alloy ◽  
Strength Increase ◽  
Solid Alloy ◽  
Material Hardness ◽  
Iron Based ◽  
Two Stages

Studies of a powder used as a modifier obtained from solid-alloy waste, such as tungsten carbide (drill balls), are presented. Dispersion, particle morphology and phase analysis of the powder were studied. The powder obtained from solid-alloy waste is a phase – it is tungsten carbide WC, it consists of nanoobjects of various shapes (nanoparticles, nanoplastics) up to 100 nm in size, with a slight presence of agglomerates up to 250 nm in size. The influence of tungsten carbide nanopowder as a modifier on the mechanical properties (strength and hardness) of PK70D3 iron-based powder structural steel has been studied. For the study, two different modes of preparation of powder alloy have been used with the use of one-stage and two-stage sintering. The influence of additive nanopowder of tungsten carbide on the mechanical properties of structural alloy powder based on iron PK70D3 has been defined: strength increases by more than 23% (in single-stage sintering), by more than 28% (in double-sintering), hardness decreases by more than 6% in single-stage sintering and increases by more than 26% with two stages of sintering, compared to the initial alloy. It has been shown that samples, obtained using double sintering with a tungsten nanopowder modifier (2.5%), have higher values of strength (more than 80%) and hardness (more than 13%), compared to modified samples, obtained by single-stage sintering technology. Thus, the modification of a 2.5 % nanoprobe of tungsten carbide, a widely used structural powder alloy based on iron PC70D3 allows for a significant change in mechanical properties. The use of powder alloys in double sintering technology provides the material hardness and the strength increase.

Towards a Fracture Energy Based Approach for Wear Prediction of WC-Co Tools in Industrial Cold Heading Process

2015 ◽  
Vol 651-653 ◽  
pp. 486-491 ◽  
Author(s):  
Colin Debras ◽  
André Dubois ◽  
Mirentxu Dubar ◽  
L. Dubar
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Contact Condition ◽  
Near Surface ◽  
Economic Competitiveness ◽  
Critical Areas ◽  
Temperature Distributions ◽  
Element Simulation ◽  
Sliding Test ◽  
Roughness Measurements

Tools sustainability and reliability is a key axis for economic competitiveness of companies in the field of cold heading of steels. This durability is currently limited by the damage occurring at the contact surfaces.The main objective of this study is to propose an energy based approach to understand the mechanisms of deterioration of the WC-Co carbide tools.Firstly a finite element simulation of an industrial cold heading process is run in order to identify the contact condition at the tool workpiece interface. Main results are the stress, strain and temperature distributions in the near surface of the tools. A particular attention is paid to the location of critical areas that may limit the tool life.Jointly, characterizations of the morphology of the worn surfaces are performed. SEM observations added to EDS and roughness measurements are done from midlife to end of life of industrial tools. Friction tests are performed with the Upsetting-Sliding Test involving contactors extracted from real worn tools to identify friction coefficients in order to provide the evolution of the friction coefficient according to the wear state of the tools. Finally, the correlation between the numerical analysis and the experimental measurement is discussed to attest to the relevance of the energy fracture based model to explain the deterioration of the tribological conditions.

scholarly journals Anisotropy of the Kinetic Friction on a Single Crystal of Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 661-668 ◽  
Author(s):  
Katutosi Tusima
Keyword(s):  
Friction Coefficient ◽  
Slip System ◽  
Single Crystal ◽  
Tungsten Carbide ◽  
Basal Plane ◽  
Kinetic Friction ◽  
Track Width ◽  
Maximum Friction ◽  
Temperature Range

Abstract Measurements were made of the kinetic friction which occurs when a tungsten carbide ball slides in various directions on the surface of a single crystal of ice, the track width produced on the surface was also measured. Anisotropies were detected in both the friction coefficient and the track width. The track width φ was at a maximum when the ball was slid normal to the basal plane and a minimum when it was moving parallel to (0001) in the temperature range —5 to —30°C. Although the friction coefficient was at a minimum when slid normal to (0001) and maximum in parallel to (0001) at temperatures of —19°C and below, this relation was found to be reversed at temperatures of —10°C and above. Anisotropy in track width can be explained in terms of the amount by which a slip system contributes to deformation in a specimen. However, our understanding of frictional anisotropy calls for knowledge of the ploughing strength p defined by the adhesion theory of friction. It was found that p reached a maximum in parallel to (0001) and a minimum normal to (0001) and that the frictional anisotropy on (0001) was influenced by the value . A remarkable frictional anisotropy was also observed on the surface inclined to the basal plane at 30°; the maximum friction coefficient was twice the minimum, whereas the maximum track width was only 1.3 times the minimum.

Comparative Study on the Tribological Performance of HFCVD Diamond and DLC Films under Water Lubricating Condition

2011 ◽  
Vol 487 ◽  
pp. 155-159
Author(s):  
Bin Shen ◽  
Fang Hong Sun ◽  
Zhi Ming Zhang
Keyword(s):  
Silicon Nitride ◽  
Friction Coefficient ◽  
Tungsten Carbide ◽  
Ball Bearing ◽  
Arc Discharge ◽  
Bearing Steel ◽  
Tribological Performance ◽  
Vacuum Arc ◽  
Dlc Film ◽  
Ball Bearing Steel

The tribological performance of conventional microcrystalline diamond (MCD) film and diamond-like carbon (DLC) film is investigated comparatively under water lubricating condition. The MCD and DLC film are deposited on cobalt cemented tungsten carbide (WC-Co) substrate using the hot filament chemical vapor deposition (HFCVD) method and the vacuum arc discharge with a graphite cathode respectively. Scanning electron microscopy (SEM), white light interferometer, and Raman spectra are employed to characterize as-deposited MCD and DLC samples. The friction tests are carried out on a ball-on-plate reciprocating friction tester, where the sliding process is conducted under water lubricating condition. Silicon nitride, tungsten carbide, ball-bearing steel and copper are used as counterpart materials. The results indicate that DLC film always exhibits lower friction coefficient than MCD film under water lubricating condition, except the case of sliding against the silicon nitride, in which DLC film is worn out very rapidly and thus leads to the high friction coefficient. The wear resistance of DLC film under water lubricating condition is significantly poorer than that of MCD film. While sliding against silicon nitride, tungsten carbide, ball-bearing steel and copper, its wear rate is calculated as 3.67´10-7mm3N-1m-1, 9.31´10-9mm3N-1m-1, 3.54´10-7mm3N-1m-1, and 4.97´10-8mm3N-1m-1respectively. Comparatively, no measurable wear track can be found on the worn surface of MCD films.

scholarly journals Structure, physical and chemical properties of near-surface layers of optical materials modified by treatment in hydrogen plasma

2021 ◽  
pp. 12-39
Author(s):  
U. O. Salgaeva ◽  
◽  
A. B. Volyntsev ◽  
S. S. Mushinsky ◽  
◽  
...  
Keyword(s):  
Optical Materials ◽  
Hydrogen Plasma ◽  
Surface Region ◽  
Soda Lime ◽  
Plasma Modification ◽  
Soda Lime Glass ◽  
Structure And Properties ◽  
Surface Layers ◽  
Near Surface ◽  
First Time

The present paper aims to investigate the structure and properties of the near-surface layers of optical materials modified by treatment in hydrogen plasma (H-plasma). For this the quartz and soda-lime glasses, lithium niobate (LN) as delivered and LN after proton exchange were used. The structure and properties of the near-surface layers of optical materials were investigated by IR spectroscopy, Raman spectroscopy, X-ray diffraction analysis, atomic force microscopy, mode spectroscopy, scanning electron microscopy, and wet chemical etching. During the treatment in H-plasma the hydrogen penetrated into the near-surface layers and caused increasing the number of defects in the structure of materials. Changes of the shape and intensity of the absorption peaks of OH–-groups and the θ/2θ- curves recorded from the LN samples processed in H-plasma were inconsequent, probably due to the thin modified layer. For the first time, a huge volume “swelling” (above 10 %) of the near-surface layers of LN and soda-lime glass after the processing in H-plasma was revealed. Also for the first time, the formation of thin strained layers on the surface of the LN after treatment in H-plasma was shown; the density reduction of the near-surface layers of the LN modified in H-plasma was described; the features of blistering and flaking were found on the surface of LN and soda-lime glass after their treatment for a long time (120–150 min). For the first time, the multilayer structure of the near-surface region of the LN was detected after treatment in H-plasma. In this paper we proposed the model of changes the structure and properties of LN after the treatment in H-plasma. The model explains the experimental results obtained in this study and previously published studies of other research groups. Due to the high concentration in the near-surface layers of optical materials after the H-plasma treatment, hydrogen predominantly forms pores and bubbles. Presumably the compounds of the Li2O–Nb2O5 system with a low Li content formed in the near-surface region of LN after the treatment in H-plasma. Modification of near-surface layers of optical materials in hydrogen plasma could be used to form elements of integrated-optical circuits, particularly the diffraction gratings.

scholarly journals Nanoscale oxygen defect gradients in UO2+x surfaces

2019 ◽  
Vol 116 (35) ◽  
pp. 17181-17186 ◽  
Author(s):  
Steven R. Spurgeon ◽  
Michel Sassi ◽  
Colin Ophus ◽  
Joanne E. Stubbs ◽  
Eugene S. Ilton ◽  
...  
Keyword(s):  
Defect Formation ◽  
Fuel Cycle ◽  
Surface Oxidation ◽  
Excess Oxygen ◽  
Interstitial Oxygen ◽  
Oxygen Defect ◽  
Near Surface ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Actinide Oxides

Oxygen defects govern the behavior of a range of materials spanning catalysis, quantum computing, and nuclear energy. Understanding and controlling these defects is particularly important for the safe use, storage, and disposal of actinide oxides in the nuclear fuel cycle, since their oxidation state influences fuel lifetimes, stability, and the contamination of groundwater. However, poorly understood nanoscale fluctuations in these systems can lead to significant deviations from bulk oxidation behavior. Here we describe the use of aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy to resolve changes in the local oxygen defect environment in UO2+x surfaces. We observe large image contrast and spectral changes that reflect the presence of sizable gradients in interstitial oxygen content at the nanoscale, which we quantify through first-principles calculations and image simulations. These findings reveal an unprecedented level of excess oxygen incorporated in a complex near-surface spatial distribution, offering additional insight into defect formation pathways and kinetics during UO2 surface oxidation.

Sign in / Sign up

Export Citation Format

Share Document