Accession Number : AD0865428

Title :   Development of Improved Cutting Tool Materials.

Descriptive Note : Final technical rept. Jun 66-Jun 69,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Cook, Nathan H. ; Nayak, P. Narayan

Report Date : 15 JUN 1969

Pagination or Media Count : 194

Abstract : When the normal stresses on the tool face are less than about half the transverse rupture strength of the tool, cratering wear of cemented carbide tools occurs by the thermally activated dissolution of the pure WC grains in the tool. Complex carbide grains are not removed in this manner but come off as discrete particles of the order of magnitude of the grain size. At any given cutting temperature, these complex carbides have only a minor influence on the cratering wear rate. The major beneficial effect of the complex carbides appears to be to reduce the chip-tool contact length. The consequent reduction in cutting temperature, at a given feed, speed, etc., leads to a marked decrease in the wear rate. At sufficiently short contact lengths, however, these effects are negated by the rise of the tool face stress to a value over half the transverse rupture strength of the tool. Catastrophic adhesive wear then sets in. A temperature-stress optimal contact length therefore exists for each type of tool material. Tool-work diffusion studies and electron microscope observations of chip surfaces provide qualitative support for the proposed wear model. The conclusions with respect to the cratering wear of high speed steel tools are generally similar to those for carbide tools. A critical stress level exists below which adhesive wear does not occur. An atomic jump model of thermally activated wear correlates the experimental data with good accuracy. (Author)

Descriptors :   (*CUTTING TOOLS, MATERIALS), CARBIDE TOOLS, STEEL, WEAR RESISTANCE, PERFORMANCE(ENGINEERING).

Subject Categories : Machinery and Tools

Distribution Statement : APPROVED FOR PUBLIC RELEASE