Diamond Drill Core Research Articles

Investigation of drilling 2D C<sub>f</sub>∕C–SiC composites with brazed diamond core drills

Abstract. Drilling carbon fiber reinforced silicon carbide composites still forms a big challenge for machining because of their special braided structure and anisotropy. In this study, through the drilling of 2D Cf∕C–SiC composites, two kinds of brazed diamond core drills with different abrasive distributions were compared. The results showed that the drilling force and torque of the two drills decreased with the increase in the spindle speed and increased with the increase in the feed speed. Under the same drilling conditions, the drilling force and torque of the brazed diamond drill with the ordered abrasive distribution were far lower than those of the brazed diamond drill with the random abrasive distribution. Also, the quality of the holes drilled by the drill with the ordered abrasive distribution was better than that of the holes drilled by the drill with the random abrasive distribution, which is attributed to the uniform abrasive spacing provided by the drill with the ordered abrasive distribution.

Depositional age and tectonic environment of the Gouap banded iron formations from the Nyong group, SW Cameroon: Insights from isotopic, geochemical and geochronological studies of drillcore samples

The discovery of the Gouap banded iron formations (BIFs)-hosted iron mineralization in the northwestern of the Nyong Group (Ntem Complex) in southwestern Cameroon provides unique insights into the geology of this region. In this contribution, we firstly report detailed study of geochemistry, isotopic and geochronology of well preserved samples of the Gouap BIFs collected from diamond drillcores. The Gouap BIFs consist mainly of amphibole BIFs and amphibole–pyrite BIFs characterized by dominant Fe2O3 ​+ ​SiO2 contents and variable contents of CaO, MgO and SO3, consistent with the presence of amphibole, chlorite, epidote and pyrite, formed during amphibolite facies metamorphism and overprinted hydrothermal event. The amphibole–pyrite BIFs are typically enriched in trace and rare earth elements (REE) compared to the amphibole BIFs, suggesting the influence of detrital materials as well as secondary hydrothermal alteration. The Post Archean Australian Shale (PAAS)-normalized REE–Y profiles of the Gouap BIFs display positive La, Eu anomalies, weak negative Ce anomalies, indicating a mixture of low-temperature hydrothermal fluids and relatively oxic conditions probably under relative shallow seawater.We present here the first isotopic data of BIFs within the Ntem Complex. The δ30SiNBS28 values of the quartz from the Gouap BIFs vary from −1.5‰ to −0.3‰ and from −0.8‰ to −0.9‰ for the amphibole BIFs and amphibole–pyrite BIFs, respectively. The quartz has δ18OV-SMOW values of 6.8‰–9.5‰ (amphibole BIFs) and 9.2‰–10.6‰ (amphibole–pyrite BIFs). The magnetite from the Gouap BIFs shows δ18O values ranging from −3.5‰ to −1.8‰ and from −3‰ to −1.7‰ for the amphibole BIFs and amphibole–pyrite BIFs, respectively. Moreover, the pyrite grains in the amphibole–pyrite BIFs display δ34S values of 1.1‰–1.8‰. All isotopic data of the Gouap BIFs confirm that they might have precipitated from low-temperature hydrothermal fluids with detrital input distant from the volcanic activity. According to their geochemical and isotopic characteristics, we propose that the Gouap BIFs belong to the Superior type.In situ U–Pb zircon dating of BIFs was conducted to assess the BIF depositional age based on strong evidence of zircon in thin section. The Gouap BIFs were probably deposited at 2422 ​± ​50 ​Ma in a region where sediments extended from continental shelf to deep-water environments along craton margins like the Cauê Formation of the Minas Supergroup, Brazil. The studied BIFs have experienced regional hydrothermal activity and metamorphism at 2089 ​± ​8.3 ​Ma during the Eburnean–Transamazonian orogeny. These findings suggest a physical continuity between the protocratonic masses of both São Francisco and Congo continents in the Rhyacian Period.

Fracture Frequency and Block Volume Distribution in Rock Masses

There are important potential engineering applications of a prediction model for rock mass block size distribution from linear fracture frequency measurements along scanlines on exposed rock walls along diamond drill cores, or along digitized borehole walls. These pertain to the characterization of rock masses in mining and geotechnical engineering projects either using rock mass classification systems or empirical equations for the reduction of rock mass parameters or numerical simulation codes. Another application is the resource estimation of decorative stone deposits using diamond drill coring or image analysis of borehole walls. In these cases, the resources are derived from the distribution of rock block volumes greater than a certain cut-off volume. It could be realized that such a prediction could lead apart from the evaluation of the measured decorative stone resources, also to the optimization of pit limits and the final estimation of proven reserves. Further, it could lead to optimization of block volume diamond wire cuts at the later stage of squaring of block volumes by comparing the final distribution after squaring with the original in situ block size distribution. Towards this aim and based on the results of a previous paper, we further elaborate: (a) on the composition of the method to characterize the fracture frequencies observed along diamond drill cores and (b) on the analytical prediction of the block volume distribution. Analytical model predictions are finally validated against actual production data from a white dolomitic marble quarry and they are compared with predictions of a more rigorous numerical simulation model based on a non-homogeneous Poisson process.

Felsic magma-water interaction in shallow intrusive environments: Timing between fluidal peperites and intrusive hyaloclastites in a jurassic cryptodome from the eastern Deseado Massif (patagonia, Argentina)

This work describes the facies architecture, morphology and textures of a Jurassic rhyodacitic cryptodome outcropping in the Don Nicolás Mine, an important Au–Ag producing mine located in the Deseado Massif, Argentinean Patagonia. The access to 70 m deep surface mining operation and to a large number of diamond drill cores offer a unique chance to explore the volcanic rock assemblage of this body, allowing to study intrusion and growth mechanisms of a shallow subvolcanic body, and also providing insights into the timing between different brecciation processes occurring during magma intrusion into a poorly consolidated and water saturated pyroclastic sequence. Facies analysis allowed to infer this body as the result of a rhyodacitic magma intruding in a single and steady endogenous inflation pulse, resulting in the development of a flow banded core and a fluidal peperite envelope due to the combination of relatively low magma viscosities (for a rhyodacitic melt), the development of stable vapor films insulating the flowing magma and also allowing the ductile deformation of the rhyodacite clasts, and the fluidization of the unconsolidated and water saturated host rocks. After the main inflation stage stopped, the collapse of the vapor films resulted in quench fragmentation modifying the originally fluidal shape of many clast at the peperites, specially at the outer portion of the breccia envelope where fluidal clast shapes were almost completely erased due to this process. At the same time water invaded the inner portions of the intrusion, causing widespread quenching and the development of intrusive hyaloclastites at the edges of the coherent facies.

Methodology for the Estimation and Classification of White Marble Reserves

In the marbel industry, ore reserves refer to the produced tonnage of orthogonal prismatic, defect-free blocks of commercial sizes and of marketable aesthetical quality. On the contrary, in the mining sector, ore reserves refer to the tonnage of ore with grade above some cut-off value. While in the mining sector ore reserves are reported according to existing standard guidelines, the marble industry has no standard method. The purpose of this paper is to present a method to estimate white marble reserves using drill coring or borehole wall logging and limited joint mapping on exposed marble surfaces. Data pertaining to fracture orientation, fracture frequency, size, and whiteness were collected. The primary phase of marble characterization is followed by the discretization of the orebody into a three-dimensional array of orthogonal prismatic blocks, where the marble whiteness and fracture intensity are attribute values. Both these variables are considered to obey continuous and not discrete probability distributions. The discretization is performed using computer aided design and the Block Kriging techniques. An outline to improve the description of a given marble ore deposit at the exploration stage is presented for the prediction of marble block size distribution from joint count measurements along diamond drill cores. An example case of a white dolomitic marble quarry is used to demonstrate these methods.

Geology Controls Grade Variance at Grasberg Cu-Au Porphyry Deposit, Papua-Indonesia

The Grasberg mining district is located in the core of the highlands of West New Guinea island, in the central ranges of the Papua Province of Indonesia. The collision between Australia Plate and Pacific Plate on Late Miocene generate NW-SE compressional structures orientation that produced reactivation of NE striking dilation to control the multiple series intrusion of host to Cu-Au porphyry deposit (Sapiie & Cloos, 2004). The oldest of Dalam Intrusion characterized by andesitic rock texture, phyllic to potassic alteration, low-moderate Cu-Au grade (0.25<EqCu<1). It is intruded by Main Grasberg Intrusion (MGI) with potassic alteration dominantly, quartz monzodioritic, high Cu-Au grade (EqCu>1). The latest Kali Intrusion characterized by propylitic to potassic alteration, quartz monzodioritic, dominant barren with EqCu is below the cut-of-grade (EqCu <0.25). The forecast block model is built in quarterly basis based on technical sampling assay method combination between diamond drill core and blasthole cutting samples. The actual grade model develop in daily basis following incremental blasthole cutting samples and be used for the ore reconciliation in monthly basis. The Cu-Au grade variance can be a loss and gain comparing to the forecast block model up to +/-30%. Focused on the negative variance or grade loss within pit radial sector 300°-330° at Dalam Intrusion and Southeast Kali host to phyllic-potassic alteration, and positive variance or grade gain observed dominantly along contact intrusion host to propylitic-potassic alteration. The veinlet relationships observed early vein bearing Cu-sulfide in NE direction intensively cut by SE and NS veins that filled by barren quartz-anhydrite±gypsum and quartz-sericite-pyrite as the latest hydrothermal fluid and affected on grade variance results. The spatial data distribution also influenced on grade variance model related to the alteration and mineralization style within the Grasberg Cu-Au porphyry deposit.

Multiple regression model for prediction of rock properties using acoustic frequency during core drilling operations

ABSTRACT The primary purpose of this study is the quantification of rock properties uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), density and abrasivity, using sound signal dominant frequencies produced during diamond core drilling operations. Rock drilling operations were performed on seven different types of rock samples, using a computer numerical control (CNC) drilling machine. Using the multiple regression analysis, satisfactory mathematical equations were developed for various physico-mechanical rock properties, as well as dominant frequencies of the sound level were generated during diamond core drilling operations. The developed prediction models demonstrated a good regression coefficient between the rock properties and dominant frequencies i.e. the R2 values are 82.50%, 78.41%, 79.40%, and 93.24% for UCS, BTS, density and abrasivity, respectively. The performances indices are: (i) root-mean-square error (RMSE) are 0.102754, 1.241652, 0.396727, and 0.697889 for UCS, BTS, density and abrasivity, respectively; (ii) values account for (VAF) is 82.50008%, 78.41137%, 79.40137%, and 93.23596% for UCS, BTS, density and abrasivity, respectively. Presently, it is in the early stages of development towards the prediction of rock properties using dominant frequencies with the help of audio signal processing in the rock drilling operation. The developed prediction models can be utilised at the early stages of mining and civil engineering projects, for the quantification of rock properties using sound signal dominant frequencies.

Crystalline-rock aquifer system of the Llano Uplift, Central Texas, USA

The crystalline-rock aquifer system of the Llano Uplift (Central Texas, USA) hosts an important local water resource that has been relatively little studied. The Uplift is a structural dome of Precambrian granitic and metamorphic rocks. Late Paleozoic normal faulting and fractures, decompressive fractures, weathering, lithology, and rock fabric control the aquifer properties. Data from driller reports (over 2,000 wells) show that wells in granites have higher median yields than wells in metamorphic rocks. There is a weak correlation of well yield with regolith thickness, and median regolith thickness is greater over granites than over metamorphic rocks. Fracture permeability, which is very heterogeneous, is the major control. Wells are shallow (generally <100 m depth), but more recent wells have been drilled more deeply. Permeability data imply decreased open-fracture density and aperture with depth, although sample bias is a consideration. Diamond drill cores show that many near-surface fractures with significant aperture are filled by rock fragments from weathered surrounding rocks and that fracture skins are thinner and contain iron oxides in a more reduced state with depth. Fracture skins can be porous, with porosity ranging to over 10%. There is a need to compare crystalline-rock aquifer systems to assess weathering, tectonics, fractures, and mineralogy/petrology to assess the characteristics of these systems, which are critical water resources in large areas of the world.

Chemostratigraphic constraints on the nature and origin of felsic schist units hosting stratabound and orogenic vein gold on Lone Star Ridge, Klondike Gold District, Yukon

Felsic schist units in the Lone Star Ridge area of the northern Klondike Gold District, Yukon, Canada, host both locally gold-bearing orogenic quartz veins and much more extensive zones of disseminated gold mineralization that is stratabound within specific schist units and is interpreted to be syngenetic in origin. Scarcity of outcrop and the difficulty in distinguishing between subtly different schist units has hampered correlation between surface exposures and drill core, and production of a detailed geological map of the area. Lithogeochemistry offers an alternative, unbiased way to map and interpret the various subunits of the felsic schist package that host disseminated gold mineralization and gold-bearing veins in parts of the Klondike, and that can potentially form the basis for correlations between various drill holes, and between drill holes and surface exposures. A detailed investigation of 4590 multi-element geochemical analyses (by 4-acid digestion) from a set of 27 diamond drill holes in the vicinity of the Boulder Lode open cut (Lone Star gold occurrence) on Lone Star Ridge has revealed several lithogeochemical signatures that correlate closely with gold content and to some extent with lithological units distinguished during initial logging of the drill core. Research quality geochemical analyses for a suite of representative rock units selected from the 2005 drill holes have been used to verify the multi-element geochemical analyses, and to determine the petrochemical character of some of the individual rock units. Results of this study demonstrate that it is possible to construct a chemostratigraphic framework for the felsic schist units in the vicinity of the Boulder Lode. Distinctive rock units can be broken out that have very consistent geochemical signatures, and elevated gold values related to the presence of disseminated gold appear to be consistently associated with specific rock units. These chemostratigraphic marker units have been utilized to constrain the geology and structure of the immediate study area, and in particular to define the geometry of the schist units that contain disseminated gold. The same approach has also been applied to a very extensive set of geochemical data (comprising nearly 34,000 individual samples) from chip samples, diamond drill core, reverse circulation drill samples, and conventional soil samples obtained during other historical and more recent exploration programs, to better resolve the geological interpretation of entire Lone Star Ridge area.

Estimating rock properties using sound signal dominant frequencies during diamond core drilling operations

In many engineering applications such as mining, geotechnical and petroleum industries, drilling operation is widely used. The drilling operation produces sound by-product, which could be helpful for preliminary estimation of the rock properties. Nevertheless, determination of rock properties is very difficult by the conventional methods in terms of high accuracy, and thus it is expensive and time-consuming. In this context, a new technique was developed based on the estimation of rock properties using dominant frequencies from sound pressure level generated during diamond core drilling operations. First, sound pressure level was recorded and sound signals of these sound frequencies were analyzed using fast Fourier transform (FFT). Rock drilling experiments were performed on five different types of rock samples using computer numerical control (CNC) drilling machine BMV 45 T20. Using simple linear regression analysis, mathematical equations were developed for various rock properties, i.e. uniaxial compressive strength, Brazilian tensile strength, density, and dominant frequencies of sound pressure level. The developed models can be utilized at early stage of design to predict rock properties.

Comprehensive optimization of process parameters in rotary ultrasonic drilling of CFRP aimed at minimizing delamination

Delamination damage is one of the main problems in drilling of carbon fiber reinforced plastics (CFRP) laminates. In recent years, rotary ultrasonic drilling, a brand new machining process that results in better machining quality, has been attracting increasing attention. An experimental investigation carried out on carbon fiber reinforced plastics laminates using diamond core drill. Diamond core drills are simultaneously drilling and grinding fiber reinforced plastics therefore improve hole quality. To this end, a proper ultrasonic system for a core drill designed and fabricated. The effects of process parameters including cutting velocity, feed rate, thickness and ultrasonic vibration on thrust force and delamination studied. Analysis of variance (ANOVA) established to examine single and multiple effects of variables on delamination and determine their contribution rate. Subsequently, Regression models in order to predict delamination through machining parameters introduced and optimized condition evaluated. The lowest delamination is observed in lower cutting velocity and feed rate by applying ultrasonic vibration on the thinner CFRP. Machining force in rotary ultrasonic drilling method compared to conventional drilling reduced. Moreover, by statistical evaluation, resulted that thickness influence on delamination is more than other variables.

Quantification of Rock Properties Using Frequency Analysis During Diamond Core Drilling Operations

Rock drilling is one of the most essential operations in mining and allied industries. This study focuses on the quantification of physico-mechanical rock properties using dominant frequencies from the sound signal generated through diamond core drilling operations. The rock drilling experiments were performed on five different types of rock samples using a computer numerical control drilling machine. Using simple linear regression analysis, satisfactory mathematical equations were developed between various physico-mechanical rock properties, namely, uniaxial compressive strength, Brazilian tensile strength, density and dominant frequencies of sound level were generated during diamond core drilling operations. The developed models can be utilised for quantification of rock properties with an acceptable degree of accuracy in realistic applications.

Very distant Sudbury impact dykes revealed by drilling the Temagami geophysical anomaly

The Temagami Anomaly is one of the largest unexplained magnetic features in North America. It is similar in size and shape to the geophysical anomaly that marks the 1.85 Ga Sudbury Igneous Complex (SIC) in its immediate vicinity but its geological cause and potential link to the Sudbury impact structure have remained elusive. Here we report on a 2200 m deep diamond drill core intersecting the area of maximum magnetic anomaly and provide evidence of diorite dykes therein being most likely related to the Sudbury impact event. The fine-grained, strongly altered biotite-amphibole diorite occurs below 2000 m, is intrusive into Archaean basement rocks and has the same major- and trace element geochemistry as the SIC, which approximates the bulk composition of the local continental crust that was hit by the impact. A crustal affinity analogous to SIC impact-melt rocks is further supported by whole-rock Nd and Pb isotopes. Low ɛNd0 between −27.6 and −18.7, as well as Nd model ages of 2.75 Ga are considered as inherited from the crustal precursor rocks that became largely homogenized in the course of impact melt formation. The 206Pb/204Pb ratios are between 15.77 and 19.38, 207Pb/204Pb between 15.22 and 15.59 (corresponding to initial 207Pb/204Pb at 1850 Ma between 15.14 and 15.22), yielding an “isochron age” of 1780 +320/−330 Ma, and the 208Pb/204Pb ranges from 35.47 to 41.15, all values that compare well with published data on SIC impact-related igneous rocks of mainly quartz dioritic composition, locally referred to as Offset Dykes, and that are distinctly different to those reported for other magmatic units in the wider region. Although several such dykes have been well known to occur both radially and concentrically around the SIC, none have been described so far from the area east of the SIC. The recognition of former intrusive impact melt at an even greater distance (50 km) from the SIC than has been known so far increases the extent of the impact structure but also the exploration potential of the area of the Temagami magnetic anomaly for Ni-Cu-PGE-sulfide deposits. The actual cause of the Temagami Anomaly remains open to debate.

Complex evolution of volcanic arcs: The lithofacies and palaeogeography of the Cambrian Stavely Arc, Delamerian Fold Belt, Western Victoria

The Mount Stavely Volcanic Complex is a Cambrian greenstone belt in western Victoria (Australia), which formed as a continental arc during subduction of the proto-Pacific plate under Gondwana. While the MSVC has been broadly described in literature, its lithofacies and palaeogeography remains unconstrained. The lithofacies that occur throughout the MSVC were characterised using field work, and diamond drill core from the Geological Survey of Victoria. The majority of the MSVC consists of fragmental facies that were deposited in a deep-marine environment. These deposits were subsequently intruded by melts, which formed the coherent facies; some became either shallow-intrusive or even extrusive. The volcanic processes that formed the Mount Stavely Volcanic Complex are similar to those currently occurring in the present-day Kermadec Arc. Furthermore the submarine nature of these volcanic facies is similar to the Cambrian Mount Read Volcanics in Tasmania.. However, in timing and cause of volcanic activity, not all of these ancient volcanic terranes are related. These findings help constrain the depositional environment in which the Mount Stavely Volcanic Complex was emplaced, which in turn provides important constraints for the tectonic reconstruction of Gondwana.

Diamond core drilling process using intermittent flushing mode

Core drilling has been the main method for exploration of solid mineral deposits, also used widely for drilling engineering geological boreholes, hydrogeological wells, etc. But the efficiency of rock destruction during diamond drilling remains fairly low, especially in some difficult conditions. The main part of power on bottom-hole is wasted to heat generation. Diamond core drilling efficiency can be improved by using pulse flushing modes, particularly with pulse drilling fluid supply. A broad classification for possible drilling methods using pulse drilling fluid supply to the downhole has been presented herein. Among the wide variety of pulse flushing options, particular attention is paid to intermittent flush drilling with alternated on/off drilling fluid supply. Proposed technology is characterized by using standard diamond drilling bits and drilling equipment. Thus, transition to the proposed technology does not require significant technical re-equipment of the process and material costs. The results of bench drilling tests with intermittent flushing were presented. A criterion for drilling with intermittent flushing was introduced. Test results had shown that transition to intermittent flushing mode allows considerably improved penetration rate (by 1.18 to 2.2 times). Power on bottom-hole value and intermittency factor will affect drilling efficiency by using intermittent flushing. It is suggested that directional utilization of frictional heat energy in the bottom-hole used for rock destruction is one of physical principles that govern improving efficiency of drilling with intermittent flushing. The technology considered allows to utilize diamond drilling’s latent reserves and can become the key technologies to improvement of efficiency of the diamond core drilling.

Performance evaluation and multi-response optimization of grinding-aided electrochemical discharge drilling (G-ECDD) of borosilicate glass

Machining of advanced glass ceramics is of great importance and is a challenging task for the modern industries. In this study, a new hybrid technique of grinding-aided electrochemical discharge drilling (G-ECDD) is attempted which combines the grinding action of a rotating abrasive tool and thermal melting action of electrochemical discharges to perform drilling of borosilicate glass. G-ECDD is performed using a normal electrochemical discharge machine set-up with a provision for using a rotating diamond-coated drill tool. The tool used is a hollow diamond core drill rather than the traditional solid abrasive tool. A spring-fed tool system was designed and developed to provide the tool-feed movement which will also help to maintain a balance between grinding action of diamond grits and thermal melting action of discharges. Preliminary experiments are conducted to identify the optimum spring force of the spring-fed system and tool rotational speed which can facilitate a balanced ECDM and grinding action for material removal. The effect of machining parameters like voltage, duty ratio, pulse cycle time and electrolyte concentration on material removal rate (MRR) and hole radial overcut (ROC) is investigated using response surface methodology (RSM). Duty ratio and voltage are found to be the most significant factors contributing MRR. Voltage and pulse cycle time are identified as the main factors controlling radial overcut of the drilled holes. Second-order regression models for MRR and ROC are developed using the data collected from the experiments using RSM. Grey relational analysis was used to optimize this multi-objective problem. A voltage of 90 V, duty ratio of 0.7, cycle time of 0.002 s and an electrolyte concentration of 3.5 M are found to be the best combination for optimizing the responses. Deterioration of bonding material and dislodging of diamond grits are found to be the major modes of tool wear during G-ECDD. The use of high-frequency pulsed DC increased the tool wear rate due to the less time available for heat dissipation between discharge cycles. Moreover, the wear at the end face of the tool will be accelerated due to the concentration of current density at edges during high-frequency operation. From the microscopic images of the machined surface, the material removal mechanisms involved in G-ECDD are found to be a combination of thermal melting by discharges, grinding action of diamond grits and high-temperature chemical etching effect of the electrolyte.

A comparison of Gaussian, Student-t and vine copulas for modelling geophysical measurements along a rock drill core

This case study is a based on measurements made approximately at 20cm lengths along a down-the-hole diamond drill core from a pyrite mine in South Australia. The measurements are the P-wave velocity, magnetic susceptibility and impedance. The trivariate distribution is modelled using Gaussian, Student-t and vine copulas and the results are compared in terms of goodness of fit and differences in extreme values from distributions obtained by simulation from the copulas. The vine copula provides the best fit for the variables. Trivariate linear spatial Gaussian, Student-t and vine copulas are used to predict magnetic susceptibility one step below the depth of the drill core. The vine copula allows for more detailed modelling of the error structure, and so provides more accurate 90% prediction intervals. The 90% prediction interval for the vine copula is wider than that for the Student-t copula, and both are wider than the interval obtained with the Gaussian copula. In general, copulas provides a more realistic modelling of geological variables and hence allows for accurate assessment of risk and uncertainty.

Power consumption of rock decomposition process during diamond core drilling using pulse flushing

The present study was based on the results of the experimental research into the process of diamond core drilling in pulse flushing mode within the frames of projects implemented by the Department of Deposits Prospecting Technique at the National Mining University (Dnipro University of Technology, Dnipro, Ukraine). The authors hereby express their gratitude to all colleagues at the Department of Deposits Prospecting Technique who took part in the experimental research.

Preparation of Ni3Al bonded diamond core drill with Ni–Cr alloy and its performance on glass–ceramic

In this study, Ni3Al was investigated as bonding material for diamond tools due to its excellent oxidation resistance and high temperature mechanical properties. Ni3Al powder was firstly prepared by self-propagating high temperature synthesis (SHS). The effect of Ni-Cr alloy content in bonding material on microstructure and mechanical properties of Ni3Al bonded diamond tools was investigated. Diamond core drills bonded by Ni3Al and Ni-Cr were prepared, and drilling performance on glass-ceramic was also examined. Results show that relative density, hardness and bending strength of diamond tool increase with the increase in Ni-Cr content. Diamond core drill bonded with Ni3Al-30 vol% Ni-Cr shows lower drilling force than that of the drill bonded with Ni3Al.

Grinding-aided electrochemical discharge drilling in the light of electrochemistry

The electrically non-conductive materials like glass, ceramics, quartz, etc. are of great interest for many applications in modern industries. Machining them with high quality and at a faster rate is a challenging task. In this study, a novel technique called grinding aided electrochemical discharge drilling (G-ECDD) is demonstrated which uses a hollow diamond core drill as the tool for performing electrochemical discharge machining of borosilicate glass. The new hybrid technique enhances the material removal rate and machining accuracy to several folds by combining the thermal melting action of discharges and grinding action of the abrasive tool. This paper presents the experimental investigation on the material removal rate during G-ECDD of glass while using different electrolytes. An attempt has been made to explore the influence of electrolyte temperature on G-ECDD performance by maintaining the electrolyte at different temperatures. Experiments were conducted using three different electrolytes which include NaOH, KOH, and the mixture of both. The results obtained from this study revealed that an increase in temperature will favor chemical etching as well as electrochemical reaction rate. Also, it was observed that heating the electrolyte leads to an increase in the bubble density and enhances the ion mobility. This causes the formation of gas film at a faster rate and thereby improving the discharge activity. Thus, machining will be done at a faster rate. Better results are obtained while using a mixture of NaOH and KOH. From the microscopic images of the machined surface, it was observed that material removal mechanism in G-ECDD is a combination of grinding action, electrochemical discharges, and chemical etching. Response surface methodology was adopted for studying the influence of process parameters on the performance of G-ECDD. The new technique of grinding aided electrochemical discharge drilling proved its potential to machine borosilicate glass and simultaneously offers good material removal rate, repeatability, and accuracy.