Some recent research on the wear behaviour of carbide cutting tools
01 Jan 1962-International Journal of Machine Tool Design and Research (Pergamon)-Vol. 2, Iss: 1, pp 43-73
TL;DR: In this paper, it was shown that the most favorable cutting conditions, from the point of view of wear, occur only if no built-up edge exists, and that in order to obtain good machinability, the most favourable structural states are those which result in an austenite phase with little carbon at the back of the chip.
Abstract: Metallographic investigations have shown that a ferrite-austenite transformation occurs in the flow layer at the back of the chip when steel is machined with carbide tools. These transformation phenomena affect the wear reactions between the carbide tools and the steel. The alpha-gamma transformation starts at relatively low cutting speeds according to the selected cutting conditions. This results in a reduction of the formation of the built-up edge until, after complete transformation at higher cutting speeds no built-up edges occur. The flank wear varies in accordance with the size of the built-up edge. Within the range of high cutting speeds, considerable influence of the alpha-gamma transformation upon the crater wear can be observed. The carbon content of the resulting austenite phase depends upon the progress of the ferrite-austenite transformation. This influences the diffusion reactions between carbide and steel, and therefore quite considerably the strength of the resulting diffusion layers. It was possible to observe that in order to obtain good machinability, the most favourable structural states are those which result in an austenite phase with little carbon at the back of the chip. In this connection it should be stated that from the point of view of low crater wear, it is not the average carbon content which is important, but the lowest possible proportion of dissolved carbon in the individual austenite crystals. For practical purposes, these experiments show that the most favourable cutting conditions, from the point of view of wear, occur only if no built-up edge exists. The formation of the built-up edge is unfavourable, not only from the point of view of wear, but also from the point of view of the quality of the machined surface.
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TL;DR: In this article, a review of the three major aspects of metal machining: the physical characteristics of chip formation, the properties and operating conditions of cutting tools, and the condition of the final product.
Abstract: This review considers the three major aspects of metal machining: the physical characteristics of chip formation, the properties and operating conditions of cutting tools, and the condition of the final product. There is a brief account of specialized metal-removal techniques and numerical and computer control of modern lathes and milling machines. The contributions of applied physics to metal cutting are emphasized throughout. The dependence of chip formation on the deformation and fracture behaviour of the workpiece and the friction conditions between chip and tool are described. Because of these extreme conditions the choice of tool materials is very restricted.
70 citations
TL;DR: In this paper, the authors examined the wear characteristics of titanium carbide (TiC)-coated carbide tool inserts during dry turning of steel workpieces and showed that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates.
Abstract: This paper examines the flank and crater wear characteristics of titanium carbide (TiC)-coated cemented carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through of the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates.
64 citations
TL;DR: In this paper, a mathematical model of the rate of flank wear is proposed, which takes into account the wear-accelerating effect of both the technological parameters of cutting and the temperature developing on the tool flank.
Abstract: Based on studies of the physical characteristics of wear processes, the conclusion could be drawn that the cutting distance must be considered not only in abrasive and adhesive processes but also in thermally-activated diffusion and oxidation processes. Consequently, it can be proposed that a mathematical model of the rate of flank wear—an autonomous non-linear differential equation that takes into account the wear-accelerating effect of both the technological parameters of cutting and the temperature developing on the tool flank—can be applied. Furthermore, this model may be used to calculate the tool life and the Taylor formula related to any arbitrarily chosen failure criteria. Technological parameters may also change periodically or continuously depending on time. The constants of the wear equation and the apparent activation energy of the process can be determined by cutting experiments and also by measurements of wear performed during factory manufacturing under a variety of technological parameters. The complex wear equation was validated by the cutting tests performed with P20 carbide on AISI1045 carbon steel. The adverse effect of rapidly changing cutting speed on the wear of the tool during vibration could be modelled.
57 citations
01 Jan 1968
TL;DR: In this article, it has been shown that different reactions take part in the tool wear when steel is machined with carbide cutting tools within the whole range of cutting speed. But the effect of different types of wear can be distinguished in the wear curves with increasing load.
Abstract: SUMMARY Basic research on the wear behaviour of tools has shown that different reactions take part in the tool wear when steel is machined with carbide cutting tools. Changes in the mechanism of wear can clearly be distinguished in the “wear–cutting speed” curves with increasing load. Dependent on the chosen cutting conditions, as for example, cutting speed, feed or the combination of work- and tool-material, considerably different kinds of wear will occur, which determine finally the tool-life of carbide cutting tools within the whole range of cutting speed. At low and medium cutting speeds increased wear of the clearance face is caused by frequent shearing of welded material between work- and tool-material by the formation of built-up edges. In these cases tool-life depends on the wear at the clearance face. When steel is machined under extreme cutting conditions, plastic deformation may occur resulting in a rapid breakdown of the cutting-tool. Within the range of high cutting speeds, diffusion reactions between chip and tool material effect an increased crater wear, which determines frequently tool-life of carbide cutting tools. Additionally an oxidation of the carbide tools at high cutting temperatures results in an outbreak of the side cutting edge. Recent investigations on the influence of non-metallic inclusion on machinability have shown that during machining special killed carbon steel the formation of sulfide and oxide layers can be observed in the contact zones of cutting tools. These layers prevent crater wear and decrease flank wear considerably in a wide range of cutting speed and improve substantially the machinability of ordinary plain carbon steel.
52 citations
TL;DR: In this article, cathodic arc ion plated chromium nitride (CrN) coatings were deposited on WC-Co substrates at negative substrate bias voltages in a range from 0 to 200 V. The performance of CrN-coated endmills in copper was also investigated correlating with the properties.
Abstract: Cathodic arc ion plated chromium nitride (CrN) coatings were deposited on WC–Co substrates at negative substrate bias voltages in a range from 0 to 200 V. The properties of CrN coatings were investigated, including the structure, hardness, adhesion and residual stress. The performance of cutting tests of CrN-coated endmills in copper was also investigated correlating with the properties. At a negative substrate bias voltage of 30 V, the adhesion strength of the coating was maximized, and the grain size became relatively small. The endmill deposited at the same bias voltage exhibited the best cutting performance of all the other samples. The cutting performance of CrN-coated endmills were superior to that of (Ti,Al)N coated endmills or uncoated endmills. The relationships between the cutting performance and film properties were discussed in terms of the wear system of the cutting tools.
48 citations
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388 citations
TL;DR: In this paper, an analog tool is introduced to enable surface finish studies to be made in the absence of feed marks and cutting force results are presented for a wide variety of cutting conditions for both resulfurized and leaded steels.
Abstract: Tests upon a variety of friction sliders reveal that, contrary to common belief, manganese sulfide is a poor solid lubricant relative to air. Lead, on the other hand, is found to be an excellent solid lubricant. An analog tool is introduced to enable surface finish studies to be made in the absence of feed marks. Cutting force results are presented for a wide variety of cutting conditions for both resulfurized and leaded steels. The built-up edge and thermal softening along the tool face lead to complex curves of cutting force versus speed. Additions of sulfur are found to promote the formation of a small built-up edge that is stable to much higher values of speed than that normally experienced with a nonresulfurized steel. Lead, on the other hand, tends to prevent built-up edge formation. Both lead and sulfur are found to produce thinner chips, promote chip curl, and to give rise to a shorter contact length between chip and tool. A discussion of the significance of the observed changes in contact length will be found in part 4 of this series.
17 citations
01 Oct 1958
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01 Jun 1956
3 citations