“Machine science and grounds of engineering” Chair, St. Petersburg State Polytechnic University (St. Petersburg, Russia):

Skotnikova M. P., Dr. Eng., Prof., Head of the Chair, Scientific Chief of Laboratory “Physical and technological investigations and electronic microscopy”, e-mail: skotnikova@mail.eu
Krylov N. A., Cand. Tech., Associate Prof.
Tsvetkova G. V., Cand. Tech., Associate Prof.
Ivanov E. K., Cand. Tech., Associate Prof.
Sokolov A. V., Post-Graduate, Engineer

The processes of grain wear in micro-cutting with a speed of 20 and 160 m/s developing in a thin superfi cial layer between abrasive grains and such billet materials as pure iron, steel and titanium alloys are studied on the example of two abrasive materials (aluminum oxide and boron nitride) via raster electronic microscopy. Surfaces guide marks, chips, platforms of wear of single abrasive grain tops have been investigated during micro-cutting of billets of the following steel grades: steel P18 (quenched), 45 (quenched), X18H10T, titanium alloy VT3-1 (quenched) and armko-iron with microhardness of 8,000; 4,600; 2,500; 2,250 and 1338 MPas, respectively. White electrocorundum 24A and the elbor of LD characterizing by microhardness of 29,000 and 70,000 MPas, as well as by heat conductivity of 13 and 2 W/m·grad, have been chosen respectively as abrasive grains. Micro-cutting was carried out at cutting speed 20, 40 and 160 m/s, until destruction of grain tops. It is shown that reduction of transversal dimensions of guide mark, chips and their segments, as well as increase of back turns between them, are observed with increase in hardness of processed materials, decrease of their ability to deformation hardening, along with lowering of hardness of abrasive tool and increase of micro-cutting speed over 40 m/s. This increase of micro-cutting speed over 40 m/s leads to change of the micro-cutting mechanism. As soon as speed of uniform plastic deformation is delayed, rotational plastic deformation replaces transmitting mode and it presents until sample destruction, as well it is characterized by localized features and is accompanied by thermal emission. Thus intensity of increase of volume wear of abrasive grains decreases.

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