Production of Superhard Carbon Rich Boron Carbon (B_(11.72)C_(3.28)) Based Composite in the B_4C-Al-WC-Co-Cu System through SHS and SPS Techniques

摘要

A superhard carbon rich B_(11.72)C_(3.28) based composite was produced via self-propagating hightemperature synthesis (SHS), by heat treatment in N gas presence, attrition milling, chemical leaching and spark plasma sintering (SPS) under N gas pressure at high temperatures. Such processing features were conducted for production (during SHS with nitrification) of the superhard B_(13)C_2, c-BN and c-BC_2N chemical compounds in the starting powder compound B_4C(68 wt.%)-Al(28 wt.%)-WCCo( 3 wt.%)-Cu(1 wt.%). The XRD results show that during SHS the boron rich boron carbon B_(13)C_2 and relatively soft (Vickers hardness lower than 40 GPa) Al-based compounds like Al_6(BO_3)_5(OH)_3, AlO(OH), Al_2O_3, Al3BC, AlB, and AlN were formed. These compounds were removed from the disintegrated composite powder by leaching with hydrochloric acid. The newly formed (via SPS) superhard light-weight composite contains 86.7 wt.% of carbon rich B_(11.72)C_(3.28) and 3.7 wt.% of boron rich B_(13)C_2 as well c-BN in a quantity of 3.3 wt.%, and precipitates of C_(11)N_4 (1.9 wt.%), WB_2 (0.9 wt.%), FeB_2 (0.3 wt.%) and graphite about 1.9 wt.%. The composite processed via SHS technology has a Vickers hardness of 40.2 GPa and the newly processed (via SPS) composite has a Vickers microhardness of ~4400HV1.0 (46 GPa), high chemical inertness in concentrated HCl acid, and thermal stability at high temperatures.