Carbide Grades Research Articles

PROPERTIES AND END USES OF CEMENTED CARBIDES

AbstractThe end uses of cemented carbides are probably more diverse than those of any other powder metallurgy product. The commonest use is to resist wear, but so many widely different wear mechanisms are encountered in practice that different grades of carbide must be produced to resist attrition, chemical erosion, micro chipping, and diffusion wear. In metal cutting high temperatures are frequently encountered, generally under conditions of severe temperature gradients so that high-temperature hardness and strength and a resistance to thermal stresses and thermal shock must be provided. Tools for operations such as wire and bar drawing, cold extrusion and cold heading require an optimum combination of hardness and strength. Generally such tools also require a very high quality of surface finish. Special measures are desirable to minimize porosity, and fortunately these also give considerable benefit from improvements in strength. Tools for mining applications show similar diversity in the properties req...

Voids in boron carbide

Two different void morphologies have been observed in the commercial grades of boron carbide that are currently undergoing assessment as candidates for the control rod material in fast breeder reactors. Some grains in unirradiated powders contain dodecahedral voids which are closely associated with iron-rich precipitates believed to be cementite, and neutron-irradiated powders also contain plate-shaped voids oriented parallel to {110} planes (rhombohedral indices). These latter voids are believed to contain fission gas and their plate-like morphology is attributed to work which the gas can do in elastically deforming the matrix if their shape is changed from spherical to disc-shape.

THE APPLICATION OF FRACTURE MECHANICS TO CEMENTED TUNGSTEN CARBIDES

The difficulties encountered in the measurement of the toughness of cemented tungsten carbides are discussed and the benefits that might be expected from an application of fracture mechanics to the problem are described. A simple method for the measurement of the fracture-toughness parameter, KIC, for the more brittle grades of carbide is considered. The method involves indenting a beam-shaped specimen with a Knoop diamond to produce a crack, and loading the pre-cracked specimen to failure in four-point bending. Results from two grades of cemented carbide are presented and show that a standard error of the mean KIC of ∼3% can be obtained from a set of 10 measurements, with a minimum of specimen preparation and no special testing equipment. The results show also that the toughness of the cemented carbide can be affected by grain-size variations within the same batch of material and by the pressing direction during manufacture.

750. Plasma measurements in interplanetary space: H Bridge and E Lyon,ESRO Plasma in Space and Lab, Rep ESRO-SP-20, April 1967, 65–91 ( Sci Tech Aerospace Reps, 5 (22), 4121, N67-37819)

Tribocor 532 is an alloy having the composition Nb-30%Ti-20%W which is produced by the conventional melting techniques used for other refractory metal alloys. The cast alloy is highly fabricable and can be readily formed into various and complex part shapes by cold working, machining and welding methods.Surface nitriding of the finished shape produces a structure of coherent hard nitrided phases dispersed in a refractory metal alloy matrix (Tribocor 532N). During nitriding, titanium nitride forms preferentially and grows as platelets within the grains of the base metal alloy. As the metal matrix adjacent to the platelets becomes depleted in titanium, niobium enters into the reaction, resulting in a final structure of complex nitrides in a Nb-Wrich matrix. The reaction produces a surface hardness in excess of low binder content hard metals (e.g WC-4.5%Co). The depth of hardness and the gradient from the surface to the core metal can be varied over considerable limits with different nitriding treatments.The corrosion resistance of Tribocor 532N has been found to be outstanding in a number of different corrosive media, including hydrochloric, nitric, phosphoric and sulfuric acids and chloride solutions. The corrosion rates over a wide range of concentrations and temperatures are far less than for common wear grades of cemented tungsten carbide. Excelent resistance to stress corrosion cracking has also been found in tensile and bend test samples evaluated in chloride and alkaline environments.

Hertzian Stress Cracks in Beryllia and Glass

The effect of Hertzian stresses resulting from loads acting at the points of contact of beryllia spheres was determined. As‐drawn glass and glass ground with various grades of silicon carbide were indented with beryllia spheres, 1 in. in diameter. Also, pairs of these beryllia spheres were pressed together. Circular cracks due to Hertzian stresses were produced; an optical technique was developed for detecting them in a beryllia surface. The outer crack radius was proportional to the cube root of the maximum applied load. Average values obtained for the respective inner crack radii were used to determine average values of the minimum load to fracture these materials. The average minimum load to fracture 1 in. diameter beryllia spheres in air at room temperature under dynamic loading was 235 1b. The crack radius in glass and beryllia was about 20% greater than the radius of the contact surface. This was not significantly affected (in glass) by flaw density. It is considered that the Hertz analysis does not give the correct location and value of the maximum tensile stress when finite displacements of material occur.

Hobbing with sintered carbide hobs

1. I N T R O D U C T I O N CYLINDRICAL gears of steel are generally cut with hobs of high speed steel. To meet the increasing demands for raising productivity as well as for cutting harder gear materials, the development of hobs with sintered carbide blades has been urged. This kind of hobs, however, has not come into practical use yet for steel gears except with those of fine modules because of technical and economic difficulties. From the technical point of view, chipping, which occasionally occurs at the cutting edges results in the distrust of users on the sintered carbide hobs. It is considered that the occurrence of chipping is due not merely to the inherent brittleness of carbides, but largely to the improper selection of carbide grade as well as cutting conditions. In USSR investigations have been made with sintered carbide hobs, in which only finishing of hardened gears has been done [1]. The purpose of this paper is to find out the optimum cutting conditions at which the sintered carbide hob can satisfactorily be used in rough cutting of steel gears. First of all, optimum carbide grade and cutting conditions were experimentally sought for the work pieces of a carbon steel by hobbing with the fly-tools on a gear hobbing machine. Then built-up types of sintered carbide hobs were tested by cutting solid gear blanks of plain carbon steel on another gear hobbing machine. The test results suggest that the sintered carbide hob makes it possible to raise productivity by increasing the cutting speed, about 200 m/min, and feedrate, 2 .0-2-5 mm/w-rev.

The wear of metallic materials by soil—practical phenomena

Cemented carbides are composite materials comprising metal carbide grains in a more ductile metallic binder. This microstructure results in a combination of high hardness and toughness, making them commonly used as rock crushing parts in rock drilling, where they usually show wear on a very fine scale. The hardness and toughness can ultimately be tuned for the application by adjusting the carbide grain size, binder fraction and composition.In the present investigation, the initial micro-scale deformation and wear of polished cemented carbide surfaces is studied by micro scratching with diamond and granite styli, and also by instrumented micro and nanoindentation. The deformation and wear is evaluated on the sub-micrometer scale using high resolution FEG-SEM and FIB cross sectioning. The selected microstructures include besides four cemented carbide grades that are commonly used in rock drilling also binderless and Ni containing grades. This wider range of cemented carbides is used to gain fundamental insights into the relations between microstructure and micro-scale deformation and wear. The results are discussed with respect to their significance for wear of cemented carbides in rock drilling operations.

Measurement of Cyclic Temperature Change of Tool-Chip Interface in Carbide Fly Milling

The tool tip temperature of a face-milling tool in machining a medium carbon steel was investigated by the tool-work thermocouple method, and the effect of the cutting condition, particularly the cutting fluid, the cutter diameter, and the work width on the temperature cycle was studied. For every rotation of the tool, the tool tip temperature builds up abruptly at the start of cut, retains a high level during the cut and is cooled during the non-cutting period. The tool-chip interface temperature during a cut depends mainly on the carbide grade, the cutting speed and the feed. The temperature at the start of the succeeding cut after cooling is also affected by those three factors as well as by the cutting fluids, the cutter diameter and the work width. The tool life date in the past investigations show that the starting temperature affects the tool life of the carbide face-milling tool.

超硬ホブに関する基礎研究

High speed hobbing with carbide hobs is one of the most urgent requirements in the production fields. The fatal difficulty for the practical utilization of a carbide hob is attributed to its unreliability due to chipping. The object of this study is to obtain the optimum conditions to avoid chipping in view of carbide grade, tool shape, and cutting condition.M20 grade of carbide and high negative rake angle are recommended for the tool tip. A larger feed rate is preferable for longer durability and higher production rate.The test result has revealed that a cut-away tool tip is highly effective from the viewpoint of cutting force, chattering, surface quality and tool life.

Effect of the size of secondary and eutectoid carbides on the properties of R18 steel

The quality of high speed cutting steel as delivered must be checked not only for its carbide grade but also for the pearlite grade.

Machinability of Nodular Cast Irons: Part III—Tool Life of Carbide and Ceramic Cutting Tools

Three grades of nodular cast iron (60, 80, and 100) were tested to determine the tool life of carbide and ceramic cutting tool materials. Tool life for all tools was much greater for grade 60 than for 80 and 100. Cast iron cutting grade carbide K6 was superior to steel cutting grade K3H, and at high speeds the ceramic was superior.

鉛快削鋼の旋削作業標準

It has not been assured yet whether free cutting steels are advantageous or not for turning operations at rather high cutting speeds with carbide tools. This report is to clarify the aforementioned problem and to establish the turning standard with carbides from the standpoint of tool life.According to the test results, the leaded free cutting steel can be turned at the speeds about forty percent higher than the case of the corresponding normal steel, if only the carbide grade is properly selected.

Machinability of Nodular Cast Irons : Tool Forces and Flank Adhesion Phenomenon

Three grades of nodular cast iron (60, 80, and 100) were tested to determine the cutting and feed forces required to machine the materials, to determine the performance of several grades of carbide and ceramic cutting tools, and to investigate the flank adhesion phenomenon. Cutting characteristics for grade 80 and grade 100 were found to be the same as for high-strength gray cast irons with similar Bhn values. Flank adhesion, with accompanying sharp increases in cutting force values, was encountered only when grade 60 was machined with carbide tools. An attempt was made to correlate tool composition and flank adhesion. In order to determine the effects of cutting conditions on flank adhesion in detail, nodular cast iron grade 60 was machined dry and wet with cast iron cutting grade and steel cutting grade carbides. Decreasing the feed rate raised the critical cutting speed at which flank build-up occurred and lowered the resultant tool force. For tools with positive rake angle, the critical cutting speed was generally higher and tool forces were lower than for tools with negative rake angle. Large clearance angle eliminated flank adhesion. The use of cutting fluids prevented flank adhesion, and tool force patterns were smooth and smaller than those for dry cutting. Flank build-up was analyzed chemically and metallurgically. Methods to prevent flank adhesion are recommended.

合金鋼SNCM 8(熱処理)の超硬正面フライス削り

The required conditions for face milling with sintered carbide blades are extremely critical, this being especially so with the case where a hardened alloy steel is machined. This is the reason why the machining standards for face milling is difficult to be estaslished. In order to overcome this, the methodological investigation for the test procedure is essential.Important factors to govern the tool life such as carbide grade, tool shape, depth of cut, feed, speed, engage angle, shock number, path ratio, etc.have been investigated experimentally.

炭素鋼S55C,S45C,S35C,S25C,S15C(焼準状態)の旋削作業標準

This report is for the project to establish the machining standards for various important metals specified by the Japanese Standard. The major items of the test are selection of carbide grades, tool shapes, speeds, and feeds for turning typical five grades of normalized plain carbon steels, and close investigation of the tool life from the viewpoint of both flank wear and crater.According to the test result, crater wear is the most serious problem in turning the carbon steels. Therefore, every effort should be made to control crater wear in selecting the best carbide grade, tool shape, cutting conditions, etc.

Machinability of Nodular Cast Irons : Tool Life Tests on Pearlitic Nodular Cast Irons

Tool life tests were conducted on nodular cast iron grades 100-70-03 and 80-60-03 with carbide and ceramic cutting tools. It was found that the cast iron cutting grade carbide wasc much superior to the steel cutting grade carbide from the standpoint of tool life and metal removal rate. With these carbides, crater wear developed at high speeds as well as flank wear in the entire speed range tested. Ceramic cutting tool had superior cutting performance. Its tool life was greater than that for the cast iron cutting grade carbide at high speeds. The slope of the tool life curve for a ceramic tool was much steeper than that for a carbide tool. Cutting performance for grade 80 nodular cast iron was not always better than that for grade 100 nodular cast iron, though grade 80 is a little softer than grade 100.

Machinability of Nodular Cast Irons : Part IV Tool Life and Variation of Tool Force with Flank Wear

Tool life tests were conducted for grade 60 of nodular cast iron with carbide and ceramic cutting tools, and the result was compared with that for grades 80 and 100. It was found that ribbon type flank build-up or smear protects the flank of carbide tool from flank wear. Tool life for grade 60 of nodular cast iron was much longer than that for grades 80 and 100. Cast iron cutting grade carbide showed better tool life than steel cutting grade carbide when machining nodular cast irons. Tool life for ceramic tool was longer than that for carbides, especially at high speeds because of steep slope of tool life diagram for ceramic tool. The wear process of carbide and ceramic tools was investigated together with the variation of tool forces due to flank wear.

Machinability of Nodular Cast Irons : Tool Life and Variation in Tool Forces with Flank Wear

Tool life tests were conducted on ferritic nodular cast iron (grade 60) with carbide and ceramic cutting tools, and the results were compared with those for pearlitic nodular cast iron (grades 80 and 100). It was found that the ribbon type flank build-up or smear protects the flank of carbide tool from flank wear. The tool life for ferritic nodular cast iron was much longer than that for pearlitic nodular cast iron. The cast iron cutting grade carbide showed better tool life than the steel cutting grade carbide when machining nodular cast irons. The tool life for ceramic tool was longer than that for carbides, especially at high speeds because of the steep slope of the tool life curve for the ceramic tool. The wear processes of carbide and ceramic tools were investigated together with the variation in tool forces due to flank wear.

Thermal Crack in the Carbide Face-Milling Cutter : 1 st Report, Results Obtained from the Fundamental Cutting Experiments

Fundamental characteristics and cause of the thermal crack which appears in the carbide face-milling cutter have been investigated. The observation of a thermal crack has revealed a lot of interesting features of the initiation and growth of the thermal crack. The cause of a thermal crack of the carbide face-milling cutter has been considered from the view-point that, as generally said, it is due to the thermal shock accompanying the intermittent cutting. Next, the influence of cutting conditions on the thermal crack has been investigated and sometimes found explainable by the above consideration. At last, several grades of carbide have been examined experimentally in respect to the occurrence of the thermal crack.

炭素鋼S55C,S45C,S35C,S25C,S15C(焼鈍状態)の旋削作業標準

This report is only the introduction of the project to establish the machining standards for various important metals specified by the Japanese Standard. The major items of the test are selection of carbide grade, tool shape, speeds, and feed for turning typical five grades of plain carbon steels, and close investigation of the tool life from the viewpoint of both flank wear and crater.According to the test result, crater wear is the most serious problem in turning the carbon steels. Therefore, every effort should be made to control crater wear in selecting the best carbide grade, tool shape, cutting conditions, etc.