Cementite Carbide Research Articles

Effect of drill gash rake angle on drillability in plain carbon and low alloy steels

In this study, the effects of the gash rake angle (γa), which is an important component of the drill geometry, on the thrust force and drilling torque occurring in the drilling of ordinary carbon steels (AISI 4140 and Ck 45) were examined through experimental and FEM-supported numerical simulation studies on surface roughness, tool surface roughness, wear and diameter deviation values were investigated experimentally. In the experiments, 6.8 mm diameter solid cementite carbide, coated and internal cooling channel drills with +10°, 0°, −10° gash rake angle were used. Three different feed rates and cutting speed levels were selected as cutting parameters. Determination of material-specific gash rake angle and cutting parameters for different materials was carried out by Taguchi-assisted variance analysis of experimental data. In experimental studies, the gash rake angle was 65.9% effective on the thrust force for AISI 4140 tempered steel, while it was the second effective parameter with 29.22% for Ck 45 manufacturing steel. While the feed rate is the more effective parameter in the drilling moments that occur when drilling different materials, it has been observed that γa also has a significant effect. It has been determined that chisel edge wear, main cutting edge wear and crater wear occur in the drill when drilling AISI 4140 tempered steel and Ck 45 manufacturing steel. The data obtained from the finite element-assisted chip removal analyses support the experimental results and provide guiding results in the selection of material-specific gash rake angle.

Magnetic domain wall dynamics studied by in-situ Lorentz microscopy with aid of custom-made Hall-effect sensor holder

We built a custom-made holder with a Hall-effect sensor to measure the single point magnetic flux density inside a transmission electron microscope (TEM, JEM-F200, JEOL). The measurement point is at the same place as the sample inside the TEM. We utilized information collected with the Hall-effect sensor holder to study magnetic domain wall (DW) dynamics by in-situ Lorentz microscopy. We generated an external magnetic field to the sample using the objective lens (OL) of the TEM. Based on our measurements with the Hall-effect sensor holder, the OL has nearly linear response, and when it is switched off, the strength of the magnetic field in the sample region is very close to 0 mT.A ferritic-pearlitic sample studied has globular and lamellar cementite (Fe3C) carbides in the ferrite matrix. Based on the in-situ Lorentz microscopy experiments, DWs in the ferritic matrix perpendicular to the lamellar carbides start to move first at ∼10 mT. At 160 mT, DWs inside the globular carbide start to disappear, and the saturation occurs at ∼210 mT. At 288 mT, the DWs parallel to the lamellar carbides still exist. Thus, these lamellar carbides are very strong pinning sites for DWs. We also run dynamical micromagnetic simulations to reproduce the DW disappearance in the globular carbide. As in the in-situ experiments, the DWs stay stable until the external field reaches the magnitude of 160 mT, and the DWs disappear before the field is 214 mT. In general, the micromagnetic simulations supported very well the interpretation of the experimental findings.

Microstructure, Mechanical Properties, and Fatigue Resistance of High-Carbon Steel for Tensile Wires Used in Flexible Pipes for Offshore Oil and Gas Transportation

Abstract Tensile armor carbon steel wires are structural elements assembled in the complex construction of flexible pipes used in the oil and gas industry. Recently, failures of flexible pipes were associated with tensile armor fractures. Despite the relevant key of these elements in the structure of flexible pipes, manufacturers and steelmakers do not provide sufficient information about the materials and their production flow. The objective of the present study was to characterize a tensile wire made of cold worked high carbon steel regarding the microstructure and mechanical properties. The microstructure was investigated by high resolution scanning electron microscopy. The steel has nearly eutectoid chemical composition (0.69 % carbon) and presents a microstructure of very fine and deformed pearlite. Some cementite carbides appeared fragmented and spheroidized in the ferrite matrix. These microstructural features are typical of patented steel, which was subsequently cold deformed by rolling and drawing. The tensile curve of the material was obtained and modeled by Hollomon’s, Voce’s and Ludwik’s constitutive equations. The S– N fatigue curve of the wire was constructed with four-point bending tests with ratio R = 0.1. The endurance limit for R = 0.1 was estimated, and the correspondent value for R = −1 was calculated based on Goodman’s relation.

Effect of casting modification materials on cutting forces of an Al12Si alloy used in aircraft technology

Abstract In this study, the effect of modification Al-12Si (Etial 140) casting alloy with Al10Sr, CuSn5, and Al10Sr + CuSn5 master alloys has been investigated with respect to the cutting forces. In order to characterize the morphology of materials used in this study, metallography, hardness, density tests, and chemical analysis were performed. An optical microscope was used to examine the microstructure of the samples. Machinability tests were performed with the turning method by using a titanium diboride-coated cementite carbide cutting tool. All experiments were carried out under dry machining conditions with three different cutting speeds and feed rates with a constant cut depth. After the turning test, scanning electron microscope (SEM) images were used to examine the build-up edge (BUE) formation on the cutting tool. It was determined that the modification process has a positive effect on increasing the density and hardness. According to the results, it was observed that cutting (Fc), feed (Ff), and tangential (Fr) forces decreased for all material groups with increasing cutting speed V. Furthermore, Fc, Ff, and Fr forces increased for all material groups with increasing feed rate f. Finally, the highest cutting forces were observed on the Etial 140 c + Al10Sr master alloy.

Analysis of the Low Service Life of a Planing Knife – A Case Study

The presented work deals with an analysis of causes of the very low service life of the new version of hand woodworking planing knife, which has replaced the original version of a planing knife. Based on the performed experimental works, chemical analysis, macroscopic and microscopic observation, SEM, diffractometric analysis, and Vickers hardness test it was concluded that the cause for the very low service life (practically the nonexistent one) of the new version of a planing knife are significant features of overheating. During the heating to the hardening temperature used steel was overheated, the cementite carbides dissolved, and the austenitic grains became coarse. The final microstructure of the used steel after hardening and tempering consists of brittle coarse martensitic needles, without any presence of the fine globular cementite carbides, accompanied by a very high amount of retained austenite. Thus, the chipping of the knife's cutting edge took place and the planer was unusable.

Analysis of the Effect of Tempering Temperature on the Formation of Microstructure and Hardness Values in SKD11 Steel

SKD11 steel is a tool steel material. SKD11 steel must have strong and tough mechanical properties. So to improve the quality and ability of SKD11 steel to accept external loads and forces, it is necessary to heat treatment. The heat treatment carried out in this research is hardening and hardening – tempering. The hardening process is carried out by heating SKD11 steel at austenitic temperature of 950 °C and holding time of 30 minutes. Then fast cooling (quenching) with water cooling media. As for the hardening – tempering process with temperature variations of 400 °C, 500 °C, 600 °C and a holding time of 60 minutes. In the as-quenching process the microstructure formed is martensite and residual austenite which cannot be transformed. Increasing the tempering temperature affects the martensite formed into tempered martensite consisting of ferrite and cementite carbide. In addition, with increasing tempering temperature the volume of carbide distribution will decrease and have a smoother shape. As the volume of carbide distribution decreases and the ferrite structure becomes more consistent, the ductility of the steel will increase and the hardness will decrease. The hardness value of SKD11 steel with hardening of 950 °C is 61.5 HRc. While the steel with hardening - tempering at a temperature of 400 °C = 57.3 HRc, 500 °C = 56.3 HRc, and 600 °C = 49,5 HRc. Increasing the tempering temperature will increase the ductility and decrease the hardenability on SKD11.

Carbide Precipitation during Processing of Two Low-Alloyed Martensitic Tool Steels with 0.11 and 0.17 V/Mo Ratios Studied by Neutron Scattering, Electron Microscopy and Atom Probe

Two industrially processed low-alloyed martensitic tool steel alloys with compositions Fe-0.3C-1.1Si-0.81Mn-1.5Cr-1.4Ni-1.1Mo-0.13V and Fe-0.3C-1.1Si-0.81Mn-1.4Cr-0.7Ni-0.8Mo-0.14V (wt.%) were characterized using small-angle neutron scattering (SANS), scanning electron microscopy (SEM), Scanning transmission electron microscopy (STEM), and atom probe tomography (APT). The combination of methods enables an understanding of the complex precipitation sequences that occur in these materials during the processing. Nb-rich primary carbides form at hot working, while Fe-rich auto-tempering carbides precipitate upon quenching, and cementite carbides grow during tempering when Mo-rich secondary carbides also nucleate and grow. The number density of Mo-rich carbides increases with tempering time, and after 24 h, it is two to three orders of magnitude higher than the Fe-rich carbides. A high number density of Mo-rich carbides is important to strengthen these low-alloyed tool steels through precipitation hardening. The results indicate that the Mo-rich secondary carbide precipitates are initially of MC character, whilst later they start to appear as M2C. This change of the secondary carbides is diffusion driven and is therefore mainly seen for longer tempering times at the higher tempering temperature of 600 °C.

Remarkable improvement in high temperature oxidation resistance of WC-12Co by the addition of CrSi2

WC-Co has excellent mechanical properties at a temperature below 700 °C, but above it, the mechanical properties of WC-Co decrease severely because of the oxidation effect. In the present study, the addition of metal silicide of CrSi2 was considered to enhance the oxidation resistance of cementite carbide. The WC-12Co compacts containing 0, 12.5, and 25 wt% CrSi2 were prepared using mechanical alloying and spark plasma sintering techniques at 1150 °C. According to the results of metallographic characterization, the sintered WC-12Co is composed mainly of WC and Co phases. The addition of CrSi2 leads to the formation of new phases as CrSi, CoSi, Co6W6C, and SiC depending on the compact composition. It is found that the WC-12Co compact with 12.5 wt% CrSi2 content exhibits a lower measured density and higher hardness compared to that of CrSi2-free compact. After the first cycle of exposure at 900 °C, the WC-12Co is severely oxidized, forming porous and crack oxide scales. On the contrary, the addition of 12.5 wt% CrSi2 shows the lowest mass gain and displays the most resistance to oxidation attributed to the formation of mainly SiO2 scales. Further increase in CrSi2 concentration, however, the alloy compact experiences breakaway oxidation after the fifth cycle of exposure. Accordingly, it can be proposed that the addition of 12.5 wt% CrSi2 is the most promising composition to allow the cemented carbide used at high temperatures and oxidizing atmospheres.

Investigation of the tool wear, surface roughness, and chip formation in the machining of ZrO2-reinforced aluminum composites

The aim of this study is to reveal how ZrO2 (zirconia) contributes to the machinability of aluminum 1050. In the first stage of this study, composite materials were produced by the vortex method by adding different amounts of ZrO2 (5%, 10%, 20%, and 30%) into commercial aluminum of 99.5% purity. Then, microstructure images of composite materials were taken under the scanning electron microscope (SEM), and the hardness of these composite materials was measured. In the last stage, the machinability tests of the composite materials were performed on the lathe under dry machining conditions at 125, 175, and 225 m/min cutting speeds and 0.03–0.06 and 0.12 mm/rev feed rates, with 1.5 mm constant depth of cut. Uncoated cementite carbide cutting tool inserts were used in machining tests. SEM images of the cutting tool inserts were taken, and the roughness values of the machined surfaces were measured. Chip samples were taken and investigated. It was observed that all the cutting tools had a Built-Up Edge (BUE) formation. Surface roughness and BUE formation increased as the feed rates were increased and decreased with increasing cutting speed. The roughness values decreased slightly and then increased again depending on the ZrO2 ratio. As the feed rates increased, a transition from ribbon chip type to the helical and saw-toothed forms was observed. It was also observed that the chip formation changed depending on the amount of ZrO2 in the composite structure.

Effect of intercritical temperature on the strain hardening of dual-phase bainite/ferrite steel

Medium-carbon dual-phase bainite/ferrite steels with different bainite and carbide volume fractions were prepared via intercritical annealing and austempering. Bainite dominated the microstructure at high intercritical temperatures, and carbides and ferrite phase dominated at low temperatures. Carbides existed in two types, undissolved alloy–cementite and vanadium carbide. The ferrite grain size was reduced to 1.22 ± 0.7 µm at 790°C. Modified Crussard–Jaoul (MC–J) model was used to analyse the strain hardening process, and the highest strain hardening rate was obtained at 755°C. The high carbide fraction at 755°C increased the ferrite dislocation density and enhanced the ferrite phase strength. The high dislocation density in ferrite and the small strength difference in bainite and ferrite enhanced the strain hardening rate at 755°C.

Advanced quantification of the carbide spacing and correlation with dimple size in a high-strength medium carbon martensitic steel

Interparticle spacing in materials science is a key parameter controlling ductile fracture. It is generally evaluated as the distance between particle centers of mass. High strength medium carbon martensitic steels contain a high density of carbides, whose size is non-negligible with respect to the distance between them. Current microstructural quantification methods do not take the shape of analyzed particles into account, thus being not necessarily relevant to materials containing a high density of particles that trigger void nucleation and ductile fracture.This work reports on the potency of a simple full field particle quantification method based on a watershed algorithm that takes the shape and spatial distribution of particles into account. Three microstructures were produced by heat treating a hot-rolled 40CrMo4 steel bar. Cementite carbide populations of each microstructure were quantified using carbon extractive replicas, conventional image processing and application of the developed algorithm. A comparison of results from a full field Voronoi tiling algorithm revealed pronounced differences in the shape of distributions. The watershed-based method was shown to allow efficient interpretation of the relationships between carbide distribution and ductile fracture features.

Two-body abrasion resistance of high carbon steel treated by quenching-partitioning-tempering process

The two-body abrasion behavior of a high carbon steel was investigated by applying quenching-partitioning-tempering process (Q&PT). Increasing the partitioning temperature from 250 to 400 °C, much carbon was consumed to precipitate the cementite carbides and thus less carbon was left to participate in the partitioning process, resulting in the decrease of the retained austenite volume fraction and refinement of blocky austenite. Compared with quenching-tempering treatment, both impact toughness and wear resistance of the steel were improved by applying a series of Q&PT treatments, which was associated with the formation of film-like and blocky austenite during partitioning stage. The abrasion behavior of the specimens was evaluated by both the reciprocating sliding test and rubber wheel test to increase the comparability and validness of the results. It is found that the initial hardness appeared to play a greater role in the wear resistance in reciprocating sliding wear, while the amount of retained austenite transformed during abrasion showed proportional relationship with the wear resistance in the rubber wheel test. A significant difference in groove characteristics was found in the rubber wheel wear test, revealing the narrow and deep grooves with plastic deformation and stretch-out ridges for Q&PT specimens and wide and shallow grooves with delamination at the edges for QT specimen.

Analysis of grey relational method of the effects on machinability performance on austempered vermicular graphite cast irons

In this study, vermicular graphite cast iron samples were operationalized to Austempering process in two different temperatures (315 and 375 °C) and three different waiting periods (60, 120 and 180 min). According to the selected cutting tools and cutting parameters, the effect of Austempering temperature and waiting period on the lifetime of the tools was investigated. The tests were conducted on a CNC milling machine by using coated cementite carbide cutting tools. The tests on tool wear were done in dry conditions, in a cutting speed of 120 m/min, a pitch rate of 0.15 mm/dev, and a depth of cut of 1 mm. Tool wear, cutting forces and average surface roughness rates of milled surfaces; which were occurred during the milling process, were analyzed by using grey relation method. It is observed that an increase of Austempering temperature leads to an improvement between 2.15 and 2.85 times in the lifetime of tools. By using grey relational analysis, the highest cutting performance was obtained with the sample with the temperature of 375 °C, and a waiting period of 120 min.

Effects of stress relief tempering on microstructure and tensile/impact behavior of quenched and partitioned commercial spring steel

The primary aim of the present study was to investigate the impacts of tempering (at 200–300 °C) on microstructure and mechanical properties of commercial spring steel of 60Si2CrV grade under “Quenching and Partitioning” heat treatment. Three different heat treatment routes were applied: (a) oil quenching and tempering at 300 °C (Q-T), (b) bath quenching at 160 °C followed by partitioning at 300 °C for 300 s (Q-P), and (c) the same Q-P treatment followed by tempering at 200 °C, 250 °C, and 300 °C for 90 min (Q-P-T), and it was found that due to the formation of tempered martensite/carbide-free bainite/retained austenite (16 vol%) structure, Q-P treatment significantly improved the tensile/impact behavior of spring steel as compared to the Q-T treatment. Moreover, stress relief tempering at 200–300 °C caused a two-fold increase in ductility (up to 9%) and manifested improved ultimate tensile strength (2022–2065 MPa) and U-notched impact toughness (64–64 J/cm2) in comparison to Q-P treatment. Further, tempering at 200–250 °C resulted in the impact fracture of steel in combination of quasi-cleavage facets with dimpled ruptured profile; tempering at 250–300 °C led to the partial transformation of retained austenite into bainite accompanied with increase in carbon content in austenite; tempering at 300 °C caused 30% decrease in impact toughness of spring steel as compared to Q-P treatment due to the formation of cementite carbide precipitation. In addition, the structural properties of spring steel in different tempering stages were analyzed using SEM, TEM, XRD, dilatometric and magnetometric measurements.

Shear Fracture and Industrial Overload Failure of Mechanical Fuse Shear Pin

The science and engineering application of fracture is attractive and complex in nature. The notch provided shear pin geometry design for lower and known stress concentration factor engineered for premature shear pin fracture failure. The shear pin is one among type of mechanical fuse, safeguard bigger industrial rotary components by premature failure. The notch provided in shear pin act as reduced notch toughness where crack initiation and propagation starts from notch surface due to overload stress in the system. Advancement in technologically of mechanical fuses is one such key area, with which design of engineered microstructure analysis of shear failure discussed extensively. In the present investigation, shear pin failure were characterized to determine root cause analysis. Visual examination of fracture surface reveals pure ductile adiabatic shear fracture and metallographic examinations reveals non uniform size of spheroidal cementite carbide particles distributed uniformly slipping in coarse ferrite matrix plane of maximum shear stress causes the reason for shear fracture phenomena during crack propagation.

Performance analysis of new external chip breaker for efficient machining of Inconel 718 and optimization of the cutting parameters

Chip control issues are common problems in finishing, semi-finishing, and machining with variable depths of cut in the turning operations of ductile steels and super alloys. Most inserts have chip breaker geometry to control chips in the turning process. However, unbroken chips still cause obstacles for automation and production management in the machining of ductile materials. In this study, a new cutting tool holder with an external chip control system was designed to break continuous chips, and the effect of the holder was examined with respect to the efficient machining of Inconel 718. The efficiency of the developed chip breaking system was investigated relative to different feed rates, machining speeds, and cutting depth by using cementite carbide inserts under dry cutting conditions. The studies were performed based on the Taguchi L16 design of experiments using a standard tool holder and a newly developed tool holder with a chip breaker. The surface quality, cutting force characteristics, temperature behaviors, and wear mechanisms of the inserts were measured to elucidate the influence of the chip breaking system on the machining process. Excellent chip breakability was achieved with respect to all the examined cutting parameters and chip morphologies. A remarkable improvement in tool wear was observed with the use of the chip breaker system for cutting parameters including a high machining speed, a low feed rate, and cutting depth combinations. Cutting forces and temperatures slightly decreased, and surface quality improved with increases in the cutting speed during external chip breaker-assisted turning of Inconel 718. The results indicated that the regression models of experimental responses were statistically significant.

Studies Regarding the Die Pressing Parameters on the Press Ability of Cementite Powders in Order to Obtained Sintered Steels

This paper presents the experimental results of the effects of the pressing speed on the press ability of the cementite powders alloyed with iron powders, in order to obtain sintered steels. Cementite or iron carbide is a chemical compound with Fe3C formula having orthorhombic crystal structure. Regarding mechanical properties, cementite is hard and brittle being important in the metallurgical processes. For the research process was used a mixture consists by cementite and iron powders (6,75%Fe3C+93.25%Fe) which was obtained by mechanical alloying technique for 30 hours. The cementite powders were produced by direct carburizing of Fe powders. The mixture was unilateral die pressing at three pressures 200, 400 and 600 MPa respectively 5 pressing speeds 10 up to 50 mm/min. The green billets were sintered in argon atmosphere and were studied by microstructural point of view. The evolution of microhardness function the pressing parameters was studied too.

The effects of cryogenic-treated carbide tools on tool wear and surface roughness of turning of Hastelloy C22 based on Taguchi method

In this study, Taguchi method has been applied to evaluate the effect of cryogenically treated tools in turning of Hastelloy C22 super alloy on surface roughness. The optimum parameters (cryogenic treatment, cutting speed, and feed rate) of turning were determined by using the Taguchi experimental design method. In Taguchi method, L9 orthogonal array has been used to determine the signal noise (S/N) ratio. Analysis of ANOVA was carried out to identify the significant factors affecting surface roughness. The statistical analysis indicated that feed rate, with a contribution percentage as high as 87.64 %, had the most dominant effect on machining performance, followed by the cryo-treated tools treatment and cutting speed, respectively. The confirmation tests indicated that it is possible to improve surface roughness significantly by using the Taguchi method. Surface roughness was improved by 28.3 and 72.3 % by shallow (CT1) cryogenic treatment and deep cryogenic treatment (CT2) applied on cementite carbide tools (UT). It found that wear resistance of tungsten carbide insert was increased by shallow and deep cryogenic treatments.

THERMODYNAMIC PRECONDITIONS OF ALLOYING EFFECT WHEN MODIFYING LOW-CHROMIC CAST IRON

It is studied the thermodynamic aspects of alloying effects during the treatment the low сhromium (3 − 5 % Cr) cast iron with Fe−Si−Mg inoculants. This effect is displayed at transformation of phase at cast iron structure. Instead ledeburite eutectic with cementite carbides Fe3C and (Fe, Cr) 3C the eutectic with carbide (Cr, Fe)7C3 is formed. Such carbide usually is formed at Chromium content no less 8 – 9 %. It is showed, what it caused the quasi-equilibrium state of cast iron during of it treatment with inoculants. On one side, the melt is the non equilibrium, because of into it presence the many microzones with higher content of Si and Mg. But on the other side the melt state at the microzones can to consider as quasi-equilibrium. In that microzones because of high carbon activity are created the conditions for carbide (Cr, Fe)7C3 forming. Such possibility it is confirmed by thermodynamic calculations. The application of the exposed effect is cause without the significantly expense to provide the substantial increasing of cast iron properties.

Redistribution of Second Phase Particles in Surface Layers of Deformed Roll

Using optical and electron microscopy and also X-ray diffraction laws were investigated of carbide phases particles redistribution in the roll near-surface layers (at surface and at distance of 0.5 mm, 2 mm from surface) made of 30CrMnSiА steel during hot deformation. There are located at borders and joints of isotropic and anisotropic fragments and also inside these fragments. Shows the dependence of carbide phases volume fraction (cementite and special carbides). There are located in different structural components and different locations of the roll surface layer. Shows a relationship carbides with dislocation substructure. Shows a gradient character in the laws of carbide phases distribution as they approach the roll surface.