ANTIFRICTION PROPERTIES OF BORON NITRIDE DURING DRY FRICTION IN GASEOUS MEDIA AND AT LOW TEMPERATURE (ANTIFRIKTSIONNYE SVOISTVA NITRIDA BORA PRI SUKHOM TRENNI V GAZOVYKH SREDAKH I PRI NIZKIKH TEMPERATURAKH),

The friction behavior of five series of boron nitride disks was studied under conditions of dry friction against nitrided 1Kh18N9T steel at 300, 273, 195 and 77K in air at a pressure of 133.322 nsq m and in argon, helium, and nitrogen at 300K. The series differed from one another by the density of the specimens. Temperature was found to have a pronounced effect on the friction coefficient and wear resistance. With decreasing temperature the friction coefficient increased from 0.17-0.19 at 300K to 0.32-0.34 at 79K, and the weight loss increased from 20-21 g at 300K to 30-32 g at 77K in a two-hour test. With increasing specific pressure the weight loss increased first fairly slowly and then sharply when a certain critical pressure had been reached. At specific pressures below critical a shiny film was formed on the specimens surface. However, at pressures above critical the film broke down. In gaseous media, friction coefficient and wear depend on the linear speed. This dependence is especially strong in nitrogen, argon, and helium, in which the respective friction coefficients increase from 0.30, 0.30, and 0.28 at a speed of 0.5 msec to 3.20, 3.50, and 2.80 at a speed of 10.5 msec. The specimen temperature in tests in air did not exceed 523K compared to 573-623K observed in tests in other gases. Author