Cemented Carbide Drills Research Articles

The effect of h-BN content on mechanical properties, microstructure and machinability of hot-pressed h-BN/Si3N4 composites

Si3N4 ceramics now face new applications and challenges in the semiconductor field. The preparation of h-BN/Si3N4 machinable ceramics incorporating 5–30 vol% h-BN via hot-pressing was carried out. This study systematically explored how the varying h-BN content influenced the composite's microstructure, mechanical attributes, and machinability. The results showed that some of the h-BN was encapsulated by growing Si3N4 grains to form an intragranular structure during the process of hot-pressing, while the remaining h-BN exhibited uniform distribution along grain boundaries. The Si3N4 phase transition in composites was inhibited by excessive h-BN, accompanied by a higher decrease in densification. The sample containing 20 vol% h-BN exhibited the best comprehensive performance, with high mechanical strength and excellent machinability. The bending strength and fracture toughness remained high at 862 MPa and 10.3 MPa m1/2, and could be effortlessly machined with cemented carbide drills. Additionally, the machinability of the composites was systematically characterized through observations of crack propagation paths, fitting of R-curves, and mechanical drilling tests.

Machinability analysis in Drilling Composites and drilling woven GFR/epoxy composites using the SPSS Method

Drilling processes in fiber-reinforced polymer composites Composite structures are essential for assembly and fabrication of parts. The economic impact of rejecting the drilled area, when reaching the assembly stage, it is important to consider the associated loss. Therefore, the motivations in drilling E-Class Fiber Reinforced Epoxy (GFRE) composites, this explains cutting conditions on torque and wear Feed, speed and pre-drill wear values. Four feeds (0.056, 0.112, 0.22, 0.315, 0.45 mm/rev) and three speeds (6.41, 12.71, 20.25, 32.03, and 50.63 m/min) and five pre-drill wear values and four artificially introduced wears) were used. Values; W = 7, 19, 26, 34 All samples are 8 mm diameter holes Drilled using a cemented carbide drill bit. Current In work, Multi-linear Regression models were used were used, Parameters of mechanical properties are related to: Thrust, torsion, peel-up, delamination, push-out delamination, Drill wear and machining parameters such as surface roughness before: feed and speed. Perforated model has high resolution; Scanning is done using flatbed color scanner, then to estimate the delamination factor, Image analysis was performed using Corel DRAW software. Multi-variable regression analysis significant coefficients of each variable, contribution is made to promotion and elimination. Laminate thickness on torque and displacement factors the results illustrate that there are significant effects. Cronbach's alpha value for the model is 0.924. Speed, Wear, Feed, Ft, T, Del.Peel, Del.Push and Ra. Results: the Cronbach's Alpha Reliability result. The overall Cronbach's Alpha value for the model is 0.924 which indicates 92% reliability. From the literature review, the above 50% Cronbach's Alpha value model can be considered for analysis

Effect of Drill Attrition on Machinability in Drilling Woven GFR Epoxy Composites

Drilling processes in fiber-reinforced polymer composites Composite structures are essential for assembly and fabrication of parts. The economic impact of rejecting the drilled area, when reaching the assembly stage It is important to consider the associated loss. Therefore, the motivations in drilling E-Class Fiber Reinforced Epoxy (GFRE) composites, this explains cutting conditions on torque and wear Feed, speed and pre-drill wear values. Four feeds (0.056, 0.112, 0.22, 0.315, 0.45 mm/rev) and three speeds (6.41, 12.71, 20.25, 32.03, and 50.63 m/min) and five pre-drill wear values and Four artificially introduced wears) were used. Values; W = 7, 19, 26, 34 All samples are 8 mm diameter holes Drilled using a cemented carbide drill bit. Current In work, Multi-linear Regression models were used were used, Parameters of mechanical properties are related to: Thrust, torsion, peel-up, delamination, push-out delamination, Drill wear and machining parameters such as surface roughness before: feed and speed. Perforated model has high resolution; Scanning is done using flatbed color scanner, then to estimate the delamination factor, Image analysis was performed using Corel DRAW software. Multi-variable regression analysis significant coefficients of each variable, contribution is made to promotion and elimination. Laminate thickness on torque and displacement factor the results illustrate that there are significant effects. Cronbach's alpha value for the model is 0.924.

Wear phenomena in different cemented carbides during rotary-percussive drilling in reinforced concrete

Rotary-percussive drilling through steel reinforced concrete not only subjects cemented tungsten carbide drill bits to intensive abrasive wear but additionally induces significant microstructural changes in the near-surface regions. These include micro-, meso- and macroscopic cracking; comminution of the WC; delamination of WC-binder interfaces; binder depletion and pore formation; partial WC dissolution and rearrangement; surface decarburization; and the creation of secondary phases within the binder.In this study, the wear phenomena in cemented carbide drill bits with different WC grain sizes (fine to extra coarse), binder contents (6–12 wt%) and binder types (Co, CoNi and Ni) have been documented, analysed and quantified. Noticeable differences between the various grades are evident.A wide range of experimental variables have been investigated covering the large proportion of real-world cases encountered in the application of these drill bits on the construction site. This paper presents a broad overview highlighting how material choice influences wear.

A semi-analytical model for predicting tool wear progression in drilling CFRP

In drilling carbon fiber reinforced polymer (CFRP), tool wear could significantly aggravate the drilling defects, and accurately predicting the tool wear progression is crucial for instructing tool change and preventing drilling defects in automatic production. The tool wear progression is usually modelled based on pure empirical methods, where the fundamental cutting interactions are neglected, and this is limited for applications. This paper established a semi-analytical model for tool wear progression prediction by combining the fundamental interaction analyses between tool and workpiece as the analytical part and regression analysis of three fitting parameters as the empirical part in drilling CFRP with a cemented carbide drill bit. The tool wear is featured and evaluated by the wear rate and the average half axis lengths based on tool wear characteristics. According to the cutting interactions between the drill bit and the CFRP workpiece, the wear rate is predicted based on the abrasive wear model and a previously proposed cutting force model. Combining the wear rate and wear geometry, the average half axis lengths are also predicted. The prediction errors of the wear rate and the average half axis lengths are less than 25% and 15%, respectively, with one test group for calibrating three coefficients. In addition, the effects of tool geometrical parameters on the tool wear progression are revealed for drilling CFRP.

Heat-Affected Zone and Mechanical Analysis of GFRP Composites with Different Thicknesses in Drilling Processes.

This article presents a comprehensive thermomechanical analysis and failure assessment in the drilling of glass fiber-reinforced polymer (GFRP) composites with different thicknesses using a CNC machine and cemented carbide drill with a diameter of 6 mm and point angles of ϕ = 118°. The temperature distribution through drilling was measured using two techniques. The first technique was based on contactless measurements using an IR Fluke camera. The second was based on contact measurements using two thermocouples inserted inside the drill bit. A Kistler dynamometer was used to measure the cutting forces. The delamination factors at the hole exit and hole entry were quantified by using the image processing technique. Multi-variable regression analysis and surface plots were performed to illustrate the significant coefficients and contribution of the machining variables (i.e., feed, speed, and laminate thickness) on machinability parameters (i.e., the thrust force, torque, temperatures, and delamination). It is concluded that the cutting time, as a function of machining variables, has significant control over the induced temperature and, thus, the force, torque, and delamination factor in drilling GFRP composites. The maximum temperature recorded by the IR camera is lower than that of the instrumented drill because the IR camera cannot directly measure the tool–work interaction zone during the drilling process. At the same cutting condition, it is observed that by increasing the thickness of the specimen, the temperature increased. Increasing the thickness from 2.6 to 7.7 had a significant effect on the heat distribution of the HAZ. At a smaller thickness, increasing the cutting speed from 400 to 1600 rpm decreased the maximum thrust force by 15%. The push-out delaminations of the GFRP laminate were accompanied by edge chipping, spalling, and uncut fibers, which were higher than those of the peel-up delaminations.

Investigation of drilling properties of AA7075/Al2O3 functionally graded materials using gray relational analysis

The present paper reports an experimental study on the fabrication and characterization of aluminum-oxide-reinforced functionally graded aluminum composites and optimization of drilling parameters on thrust force and average surface roughness using gray relational analysis. For this purpose, AA7075/Al2O3 functionally graded materials were produced with three layers that have different ratios of Al2O3 via high-temperature isostatic pressing and powder metallurgy method. Hardness behaviors of the layers were determined. Further, microstructural characterizations of the layers were carried out. Functionally graded materials were machined at dry cutting conditions with a 6 mm uncoated cemented carbide drill bit. The drilling experiments were carried out under different conditions such as point angles, helix angles, and feed rates, while the 25 m/min cutting speed was kept constant. The effects of factors on thrust force and surface roughness were evaluated using analysis of variance and gray relational analysis in full factorial experimental design. The minimum thrust force was measured at 221 N in a 140° point angle, 15° helix angle, and 0.075 mm/rev feed rate. Results of the gray relational analysis showed that feed rate was the dominant factor on thrust force and average surface roughness. Consequently, the highest and lowest gray relational grades were obtained at 0.899 and 0.374, respectively.

Near-surface phenomena occurring in cemented carbides with different binders during rotary-percussive drilling of reinforced concrete: FE simulation and microstructural investigations

Rotary-percussive drilling through steel rebar in reinforced concrete subjects drill bits to intensive thermomechanical loading and wear. Significant microstructural changes occur in near-surface regions. These include, but are not limited to, micro- and mesoscopic cracking; fracture at WC-binder interfaces; WC comminution; partial WC dissolution and rearrangement; surface decarburization; binder depletion and pore formation; and the creation of secondary phases within the binder [1–4].Cemented carbide drill bits with three different binders (Co, CoNi and Ni) were drilled in steel reinforced concrete. After sectioning the drill bits, numerous analysis methods were employed to identify the type and composition of phases present; to characterize microstructural changes and wear phenomena; and to locally measure the properties of the modified surface microstructure. Noticeable differences between the binder types are evident.A variety of finite element (FE) simulation methods were used to describe the thermo-mechanical loading spectrum acting on the drill bits. Transient (dynamic) impact loading and quasi-static indentation simulations calculated the stresses and temperatures generated in the application. The magnitude, orientation vectors and spatial distribution of the simulated stress and temperature fields were correlated with the experimental findings regarding crack initiation sites and regions experiencing thermo-mechanically induced surface microstructural and compositional modification. This paper presents some of these findings from extensive experimental and simulation studies.

Hole-quality evaluation in drilling fiber-reinforced composites

This paper presents a novel approach for a complex evaluation of the quality of drilled holes in fiber-reinforced composite materials. The proposed methodology is based on non-destructive quantification of visible defects based on the numerical analysis of drilled hole images. Automatic contour definition and profile formation for the uncut fibers and delamination were implemented via modularized algorithms. Four criteria for the evaluation of the defect height and width distribution were developed and combined into an overall quality parameter, Q. The methodology was validated experimentally by drilling carbon-fiber-reinforced polymer (CFRP) samples with a cemented carbide drill bit. The results showed a linear relation between the hole quality Q, the drilled hole number, and tool wear.

Assessment of Cutting Performance of Cemented Tungsten Carbide Drills in Drilling Multidirectional T700 CFRP Plate

The drilling of carbon fiber reinforced polymer (CFRP) plate is very critical in its structural applications in aeronautical, aerospace, and automobile industries. For ensuring the good quality of drilled holes in terms of least drilling damage and prolonged tool life, suitable selection of drill geometry and material, and drilling parameters—such as cutting speed and feed rate—are imperative in the drilling of CFRP plate. This study aims to evaluate the cutting performance of conventional two-flute twist drills made of cemented tungsten carbide YG6X (WC-6 wt % Co) for the dry drilling of the multidirectional T700 CFRP plate. The effects of varying cutting speed and tool wear pattern on the drilling performance are analyzed. The drilling performance is assessed in terms of hole quality by the qualitative and quantitative analysis of drilling-induced delamination and hole diameter. Furthermore, the correlation between the tool wear progression and the drilled hole quality is established. Through this assessment, a suitable set of drilling parameters, i.e., cutting speed of 9000 rpm and feed rate of 400 mm/min, is proposed for producing the best quality holes for multidirectional T700 CFRP plate.

Application of Colding tool life equation on the drilling fiber reinforcement polymers

Fiber reinforcement polymer (FRP) is a hard-to-treat material used in different areas of up-to-date machine building. It has excellent mechanical properties making the material unique in different engineering solutions such as aircraft, aerospace and boatbuilding. The optimization of holemaking operations in FRP is the main aim of the current investigation. This paper presents an approach of defining the most effective cutting data and costs of drilling Saab’s carbon fiber reinforcement plastic (CFRP) using cemented carbide and PCD drills. The experiment results included force and torque monitoring, tool wear defining and holes quality analyzing.

Rotary ultrasonic drilling of needle-punched carbon/carbon composites: comparisons with conventional twist drilling and high-speed drilling

Drilling of carbon/carbon (C/C) composites is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous, and low thermal conductivity, which can result in tear, burr, poor surface quality, and rapid wear of tools. Three drilling methods including conventional twist drilling, rotary ultrasonic drilling, and high-speed drilling can all be used in hole making of composites in industry. To find a best method of hole making in drilling of C/C composites, a serials of comparison experimental tests using the same size cemented carbide drill are designed and performed in this paper. Thrust force, tool wear, and drilling defects are all analyzed and compared for different machining parameters for all the three drilling methods. The experimental results show that rotary ultrasonic drilling is the best choice in almost all these aspects in drilling of needle-punched C/C composites within the range of selected experimental machining parameters.

Drilling analysis of cemented carbide drills after chemical treatment under low heating

This work was carried out in the shop floor of a chemical filters manufacturer. These filters are typically used by petroleum and chemical industries. They are called mirrors and are made in thick carbon steel plates, on which the holes are held. Special drill with carbide inserts and internal channels for cutting fluid supply at the drill tip was used. The carbide inserts were coated with PVD multilayer based on AlCr. The mirror manufacturer was interested in improving its productivity. At the moment of this research, the company had already made several attempts to improve their productivity, especially searching for collaboration with machine tool manufacturers. Such attempts have resulted in the use of a kind of special drill that has come to be applied in this study. The main aim of this work was to propose a new procedure to reduce wear of cemented carbide drill inserts. This new procedure consists of applying on the cemented carbide inserts a lubricant called Militec followed by heating it at 80 °C for 30 min. This product is commonly used to lubricate motors and engines. The results showed that the use of the proposed new procedure was a promising way to protect inserts against the wear in the case of drilling process investigated in the present work. The support for this conclusion was based on the inserts wear reduction of about 37% when compared with the untreated inserts.

Surface degradation mechanisms of cemented carbide drill buttons in iron ore rock drilling

The wear behavior of cemented carbide rock drill buttons is influenced by many factors, which include the composition and microstructure of the cemented carbide material, the nature of the rock material, and the conditions of the rock drilling operation. Depending on the type of rock and on the drilling procedure used, the cemented carbide is exposed to substantially differing mechanical and thermal conditions. In the present study, the surface degradation and wear mechanisms of cemented carbide drill buttons exposed to iron ore rock drilling have been characterized based on a combination of high resolution scanning electron microscopy (SEM), focused ion beam cross-sectioning (FIB), energy-dispersive X-ray spectroscopy (EDS) and electron back scatter diffraction (EBSD).The results show a significant difference in surface degradation and wear between the front and peripheral buttons of the drill bits. While the front buttons display a relatively smooth worn surface with shallow surface craters the peripheral buttons display a reptile skin pattern, i.e. plateaus, 200–300µm in diameter, separated by valleys, typically 40–50µm wide and 15–30µm deep, The reptile skin pattern is obtained in regions where the peripheral buttons are in sliding contact against the drill hole walls and exposed to high surface temperatures caused by the frictional heating. The results indicate that the reptile skin pattern is related to friction induced thermal stresses rather than mechanical contact stresses, i.e. the reptile skin pattern is formed due to thermal fatigue, rather than mechanical fatigue, caused by the cyclic frictional heating generated at the cemented carbide button/iron ore interface.

Bionic surface design of cemented carbide drill bit

The development of a high-performance cemented carbide drill bit is of great significance to the reduction of rock drilling-cost. The non-smooth features of a biological surface provide an insight into how they can obtain low friction and good wear resistance with evolving surface morphology. By analyzing the mechanism of the surface of a dung beetle for reducing soil wear and adherence, we design a cemented carbide drill bit with a bionic surface, which is expected to have superior anti-wearing and anti-sticking properties for drilling the soft coal seam. Inspired from the characteristics of the head and pronotum surface of the dung beetle, optimized non-smooth surface of the drill bit was constructed. The working performance of this innovative drill was experimentally tested. With comparative experiments under the identical drilling conditions, the wear rates, drilling times of conventional drills and bionic drills were measured. Compared with the conventional counterpart, the drill designed exhibits better performance in reducing wear and sticking drilling-breaks, therefore achieving higher levels of efficiency. The diameter of the dome and pit on the bit surface is in the range of 0.8–1.2 mm, and the bionic drill bits could get better performance with preferable drilling speeds and wear rates.

Experimental Investigations on Drilling Characteristics of Cenosphere Reinforced Epoxy Composites

In the present paper, the experimental investigations on drilling characteristics of cenosphere reinforced epoxy composites with cemented carbide drill have been presented. The drilling aspects such as thrust and hole surface roughness have been performed as function of four process parameters, namely, spindle speed, feed rate, drill diameter and % weight of the filler. Composite specimens were prepared with 20%, 40% and 60% by weight of cenosphere filler in epoxy resin as the matrix. The full factorial design (FFD) has been employed for conducting drilling experiments and the proposed drilling characteristics were analysed using response surface methodology (RSM) based quadratic models. The response surface analysis reveals that the addition of cenosphere as filler in epoxy resin appreciably decreases with the thrust and hole surface roughness for the developed composites.

Tests of Drills during Drilling Holes into Alloy Wheels

This article is interested about drilling the holes to the alloy wheels. Tested were drills to drilling holes for screws and service holes. For screw holes was tested the three-stage drill with inserts from polycrystalline diamond. Drilled are two different diameters and the transition spherical or conical surface. The service holes were drilled with cemented carbide drill availible from Mapal labeled Mega-drill-Alu-180. During test, was modified the geometry of the drill and we watched what will be the effect of applied modification. Tested was seven variants of regrinding the drill. We evaluate the surface roughness, but also if the drill has the right position and not be pushed away from its axis. Finally was tested drill with three edges. This drill bit is from company Mapal labeled Tritan.

Microstructure and mechanical properties of ZTA/BN machinable ceramics fabricated by reactive hot pressing

Abstract Zirconia-toughened alumina (ZTA)/boron nitride (BN) machinable ceramics have been successfully fabricated by reactive hot pressing. BN was in-situ introduced into the composite by the reaction of aluminum nitride (AlN) and boric acid (H3BO3). The microstructure of ZTA/BN composite was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The results indicated that BN grains were uniformly and compactly distributed among Al2O3 and ZrO2 grains. The relative density, flexural strength, fracture toughness, and Vickers hardness increased with increasing temperature. The flexural strength and fracture toughness of the ZTA/BN composite with BN content of 12.5 vol% sintered at 1800 °C achieved high values of 731 MPa and 7.48 MPa m1/2, respectively. These values were much higher than those of the composite with the same composition prepared by conventional powder sintering method, and even higher than those of the monolithic ZTA ceramics. The enhancements of the fracture strength and fracture toughness were primarily ascribed to the reactive hot pressing method which introduced BN in-situ and prevented the aggregation of BN and reduced the flaw sizes. The ZTA/BN composite exhibited excellent machinability and could be drilled using conventional cemented carbide drill bits.

The role of FE simulation in the optimisation of hardmetal rotary-percussive drill bits and cold forming tools

This paper demonstrates the significant role of finite element (FE) simulation/modelling in the optimisation of cemented tungsten carbide drill bits and forming tools. Two case studies are presented, one from the development phase for a new product and the other from the continuous improvement process during mass production. Additionally, a number of important issues are raised concerning the material property data used for FE simulation, the interpretation of results generated, and approaches to bring FE a step closer to simulating real components and operating conditions with greater predictive accuracy regarding the failure probability of the component in service.

Fabrication and characterization of B4C-based ceramic composites with different mass fractions of hexagonal boron nitride

In this paper, hexagonal boron nitride (hBN) was introduced into boron carbide (B4C) and B4C-based ceramic composites with different mass fractions of hBN were fabricated via hot pressing. The phase composition, microstructures, mechanical properties, and machinability of the B4C-based ceramic composites were investigated. The tribological properties of the B4C-based ceramic composites against AISI 321 austenitic stainless steel under dry sliding conditions were also studied. It was found that, with increasing the content of hBN, the bulk density, relative density, bending strength, fracture toughness and Vickers hardness of the B4C-based ceramic composites decreased, while the porosity increased. When the content of hBN came up to 20wt%, the B4C-based ceramic composites could be machined easily by using cemented carbide drills. The addition of hBN into the B4C matrix improved the tribological properties of the B4C-based ceramic composites due to the formation of a tribofilm consisting of boron and metal oxides.