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Wear and friction studies of nickel-tungsten carbide-graphite composites
BOOK REVIEWS
234
The mechanism of wear of rock-cutting tools and the controlling factors are reviewed. The most significant improvement in WC-Co tools can be obtained by freedom from porosity and the use of carbide grains that are structurally as perfect as possible. The latter gives both maximum resistance to fracture and better retention of properties to higher temperatures. Other improvements are also largely directed at increasing the fracture resistance of the carbides. Powder-metal-based
friction material. A. Jenkins, pp. 503-5r8,5 figs., 13 refs. Production methods and the formulation als are briefly described. Typical applications equivalent organic-based materials are made. Wear and friction
studies
of nickel-twagsten
of powder-metal-basedfrictionmateriare given and comparisons with the
carbide-graphite
composites.
J. S. Hirschhorn and E. M. Daver, pp. 519-537, 17 figs., 2 tables, I ref. Wear and friction studies have been carried out on pressed and sintered composites of 75-95 o/0theoretical density. Wear resistance correlates well with the ratio of the volume fraction of WC to that of graphite; there is a minimum weight loss at a ratio near unity. This effect is explained in terms of powder coating with graphite which affects grain-boundary formation and grain growth; supporting metallographic evidence is given. Wear rate increases with debris particle size. Residual porosity in the materials reduces wear resistance. The wear rate does not correlate with hardness or coefficient of friction; results in oil or water are very similar to those for air. Turning and drilling of some typical sintered steels. S. A. Kvist, pp. 538-565; 15 figs., IO tables, 7 refs. Turning and drilling tests have been carried out on nine different materials. The best surface finish is obtained with the highest possible speed and low cut depth. Addition of 0.59/o sulphur resulted in the lowest specific cutting force, a good surface finish and the longest tool life. Density had no influence in tool wear. Machining recommendations are given for turning and drilling the various materials. The wear rate of carbide cutting tools.
E. M. Trent, pp. 566-581, II figs., 7 refs. The wear processes that are significant on those parts of the tool/work interface where seizure is complete are considered separately from those in areas where contact is localised and intermittent. Examination of worn tools suggests that two major wear processes take place on cemented carbide under each of these sets of conditions. The influence of powder metallurgical processing variables in the production of cemented carbide tools is considered in relation to each of the main wear processes. The tribological aspects of metal-bonded diamond grinding wheels. J. R. Chalkley and D. M. Thomas, pp. 582-596, I fig., I table, 8 refs. The field of metal-bonded diamond grinding wheels and saws is described. A theoretical approach to the subject is considered. The close association of grinding with tribology is emphasised and it is stressed that the lubrication during grinding operations is the dominant factor in achieving maximum efficiency and economy. The metal Wear, 15 (1970) 231-235
234
The mechanism of wear of rock-cutting tools and the controlling factors are reviewed. The most significant improvement in WC-Co tools can be obtained by freedom from porosity and the use of carbide grains that are structurally as perfect as possible. The latter gives both maximum resistance to fracture and better retention of properties to higher temperatures. Other improvements are also largely directed at increasing the fracture resistance of the carbides. Powder-metal-based
friction material. A. Jenkins, pp. 503-5r8,5 figs., 13 refs. Production methods and the formulation als are briefly described. Typical applications equivalent organic-based materials are made. Wear and friction
studies
of nickel-twagsten
of powder-metal-basedfrictionmateriare given and comparisons with the
carbide-graphite
composites.
J. S. Hirschhorn and E. M. Daver, pp. 519-537, 17 figs., 2 tables, I ref. Wear and friction studies have been carried out on pressed and sintered composites of 75-95 o/0theoretical density. Wear resistance correlates well with the ratio of the volume fraction of WC to that of graphite; there is a minimum weight loss at a ratio near unity. This effect is explained in terms of powder coating with graphite which affects grain-boundary formation and grain growth; supporting metallographic evidence is given. Wear rate increases with debris particle size. Residual porosity in the materials reduces wear resistance. The wear rate does not correlate with hardness or coefficient of friction; results in oil or water are very similar to those for air. Turning and drilling of some typical sintered steels. S. A. Kvist, pp. 538-565; 15 figs., IO tables, 7 refs. Turning and drilling tests have been carried out on nine different materials. The best surface finish is obtained with the highest possible speed and low cut depth. Addition of 0.59/o sulphur resulted in the lowest specific cutting force, a good surface finish and the longest tool life. Density had no influence in tool wear. Machining recommendations are given for turning and drilling the various materials. The wear rate of carbide cutting tools.
E. M. Trent, pp. 566-581, II figs., 7 refs. The wear processes that are significant on those parts of the tool/work interface where seizure is complete are considered separately from those in areas where contact is localised and intermittent. Examination of worn tools suggests that two major wear processes take place on cemented carbide under each of these sets of conditions. The influence of powder metallurgical processing variables in the production of cemented carbide tools is considered in relation to each of the main wear processes. The tribological aspects of metal-bonded diamond grinding wheels. J. R. Chalkley and D. M. Thomas, pp. 582-596, I fig., I table, 8 refs. The field of metal-bonded diamond grinding wheels and saws is described. A theoretical approach to the subject is considered. The close association of grinding with tribology is emphasised and it is stressed that the lubrication during grinding operations is the dominant factor in achieving maximum efficiency and economy. The metal Wear, 15 (1970) 231-235