Friction and wear properties of spark-plasma-sintered α-AlB12 and SiB6 powder compacts in water

Tribological Behaviors of B₆O/Si₃N₄ and B₆O/Al₂O₃ Sliding Pairs in Water

“…In that study, however, we observed films of Al 2 O 3 , Al(OH) 3 and SiO 2 , and not H 3 BO 3 , on the wear tracks of the AlB 12 and SiB 6 powder compacts. 4) Therefore, it was considered that extremely thin low-friction H 3 BO 3 films were formed on the wear tracks of the AlB 12 and SiB 6 specimens, and that the formation of the films caused the low friction coefficients of the AlB 12 /Si 3 N 4 and SiB 6 / Si 3 N 4 sliding pairs. 4) We conjectured that most of the H 3 BO 3 films were promptly removed during the friction tests with the AlB 12 /Si 3 N 4 and SiB 6 /Si 3 N 4 sliding pairs, because H 3 BO 3 easily dissolves in water.…”

“…4) Therefore, it was considered that extremely thin low-friction H 3 BO 3 films were formed on the wear tracks of the AlB 12 and SiB 6 specimens, and that the formation of the films caused the low friction coefficients of the AlB 12 /Si 3 N 4 and SiB 6 / Si 3 N 4 sliding pairs. 4) We conjectured that most of the H 3 BO 3 films were promptly removed during the friction tests with the AlB 12 /Si 3 N 4 and SiB 6 /Si 3 N 4 sliding pairs, because H 3 BO 3 easily dissolves in water. 4) Besides, it has been reported that the vapor pressure of H 3 BO 3 is 1.6 © 10 ¹2 Pa at 25°C, 27) while the XPS spectra of each powder compact were obtained in a high vacuum of 10 ¹6 10 ¹7 Pa in our present study.…”

“…3) In an earlier study by our group, AlB 12 and SiB 6 ceramics showed low friction coefficients and high wear resistance in water when Si 3 N 4 , SiC and Al 2 O 3 balls were used as the paired materials. 3,4) These borides also have high hardness and corrosion resistance, in addition to favorable friction coefficients, and thus can be potentially applied as sliding parts in water. Dense AlB 12 -and SiB 6based ceramics, however, are very difficult to obtain by the hot pressing of blended elemental powders, as the Al and Si content in the blended powders oxidizes very easily during sintering, even in an Ar gas atmosphere at high temperature.…”

“…3) For this reason, the AlB 12 13) For the present study, therefore, we decided to fabricate B 6 O powder compacts by spark plasma sintering (SPS), and evaluate their tribological behaviors by sliding the B 6 O powder compacts against commercially available Si 3 N 4 and Al 2 O 3 bearing balls in water at room temperature because both the Si 3 N 4 and Al 2 O 3 balls exhibited low friction coefficients when these balls were slid against the borides such as AlB 12 and SiB 6 . 3,4) 2. Experimental Procedures B 6 O powder was obtained using methods similar to those reported by Solodkyi et al 16) First, B 2 O 3 powder was dissolved in water and mixed with B powder to obtain a mole ratio of B 2 O 3 :B = 1:14.…”

“…All of the powder compacts were then ultrasonically cleaned in a 1:1 mixture of acetone and petroleum benzene for 1200 seconds. 3,4,18,19) The microvickers hardness of each B 6 O powder compact was measured five times using a Shimadzu HMV-1 hardness tester at a load of 9.8 N, for a loading time of 15 seconds. The fracture toughness of each powder compact, meanwhile, was investigated by the indentation fracture method.…”