CERMET CUTTING TOOLS, PROPERTIES AND PREDICTION OF PERFORMANCE
Abstract
Metal cutting is a major industrial activity in the United States. Every year, millions of tons of metals are turned into chips through machining. The progress in machining technology depends, to a great extent, on the knowledge of what happens at the cutting edge of the tool as it is what happens at the tool/workpiece interface that determines the performance of tools, the quality of the machined surface and the machinability of metals. Several factors contribute to the continuous demand of the development of cutting tool materials: (1) The continuing increase in production rates. (2) The development of structural alloys with their decreasing machinability. (3) The increasing use of automated and numerically controlled machine tools and systems requiring higher degree of reliability and predictability of tool performance. During the last two decades there has been a noticeable increase in the quality of cutting tools since more research was devoted to investigate new tool materials and develop the existing ones. The CERMETS are recent entry in the growing list of commercial cutting tools. The word CERMET is a combination of the words (CERAMIC) and (METAL). Its material is a mixture of Aluminum Oxide, a ceramic, and Titanium Carbide, a metal. The excellent performance of those CERMETS within a surprisingly wide range of application is expected to result in a rapid, steady, and increasing usage during the next decade. In this research, the following steps have been achieved: (1) A simplified table that provides an overall qualitative prediction of the tool performance based on its properties and its interaction with the work material under different cutting conditions has been achieved. (2) Actual turning tests have been conducted using three selected CERMET grades and cutting two different steels (AISI 1080 and AISI 4140). The experiment outline was set to evaluate the effects of the following factors on the tool performance using the value of the flank wear (inch x 10('3)) as the measured variable. (a) Cutting conditions: Speed (V) (SFPM), Feed (f) (inch/rev), time (t) (min); (b) The workpiece material measured by its unit horsepower (U) (HP min/in('3)); (c) The following tool material properties: Hardness (H) (R(,A)), Rupture Strength (S) (PSI), Grain size (G) ((mu)m), Specific Weight (SW) (1b/in('3)), Thermal Conductivity (TC) (watt cm('-1)k('-1)). (3) After collecting data: (a) A multiple classification analysis of variance (ANOVA) was performed and extended to regression analysis where the dependency of the flank wear on the selected variables was established. (b) Metallurgical analysis and diagnosis of the failure mechanism of the used inserts were conducted using the Scanning Electron Microscope to verify and support the qualitative prediction scheme. The research led to the following general conclusions: (1) The performance of the CERMET cutting tools is significantly affected by: (A) The cutting speed and feed. (B) The tool material grain size and hardness. (C) The value of the work material unit horsepower. (D) The interaction effect between the tool and the workpiece material. (2) The joint functional relationship of the tool flank wear with the factors considered is found to be: w = 7 x 10('-6) x U('52.8) x V('1.28) x t('.61) x G('-.717) x f('.52) x H('2.64); (3) The joint functional relationship of the flank wear rate with the factors considered is found to be: w('1) = 1.4 x 10('-2) x V('1.4) x U('29.3) x G('-.506) x f('.55); (4) The interaction effect of the tool-workpiece is the result of a unique combination of the workpiece and tool material properties. This combination suggests that, through a proper selection procedure of both, the tool performance is optimized.
Degree
Ph.D.
Subject Area
Industrial engineering
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