Investigation of hBN powder lubricating characteristics of die steel H13–ceramic Si₃N₄ tribopair at 800 ℃

Abstract

In the background that hot-working die steels have been widely used in the hot stamping process of high strength steels for manufacturing car bodies and parts, solid lubricant materials are promising for decreasing the friction and wear on die surfaces at high temperatures. In this work, hexagonal boron nitride was used to lubricate the sliding interface of ceramic Si3N4 against die steel H13 at 800 ℃, and its frictional behavior was investigated at different contact pressures and rotating speeds by pin-on-disk testing. Tribological characteristics of hexagonal boron nitride solid lubricant were analyzed through 3D laser scanning confocal microscope and energy-dispersive spectroscopy. The results show that the wear behavior of hexagonal boron nitride powder lubricating film featured two stages: gradual undermining and complete damage. The formation-broken dynamic cycle of partial lubricating film constantly occurred at the frictional interface until the film was completely destroyed. In a short period, the hexagonal boron nitride lubricant can reduce the friction coefficient efficiently compared with dry friction, and the die substrate showed basically no abrasion because a layer of plasticity accumulated on the die surface, which protected the substrate. In a certain range, the boundary-lubricating film became damaged rapidly with increasing load, and high speed was not conducive to the stability of the lubricating film.

A current review on boron nitride nanotubes and their applications

“…By using the 10 B isotope as a reactant or boron source, BNNTs enriched with 10 B can be synthesised by any of the above synthesis techniques. It is well known that nanotubes and nanowires have exceptional aspect ratios, hence are used as fillers in nanocomposites to improve mechanical properties such as Young's modulus, and hardness [97] and researchers have determined that the thermal and electrical conductivity of CNT nanocomposites significantly increase when high aspect CNTs were used as fillers [98].…”

“…BN in particulate form has several applications in different fields, viz. lubricants [10], fillers [11], coatings [12], cutting tools [13], cosmetics [14], abrasives [15] and in semiconductor devices [16]. Hexagonal BN is structurally similar to graphene [17], hence is capable of forming nanotubes.…”

Solid Lubrication at High-Temperatures—A Review

“…A reduction in HT CoF and wear rate was seen for Ni-based composite due to a synergism of Ag and hBN [ 81 ]. An extensive review points to 5–15 vol% of hBN as the optimal reinforcement in the composites to impart effective lubrication at a temperature range of 600–900 °C [ 81 , 82 , 83 ]. A larger hBN concentration resulted in significant deteriorating mechanical properties of materials.…”

“…A larger hBN concentration resulted in significant deteriorating mechanical properties of materials. Figure 7 demonstrates the effect of sliding temperature on CoF and relative wear rates for various hBN based solid-lubricating materials available in recent literature [ 80 , 81 , 82 , 83 , 84 , 85 , 86 ]. The relative wear rate values are calculated after dividing the wear rate value at the reported temperature by room temperature (RT) value.…”

“… HT sliding results of hBN-based composites and coatings as found in recent literature ( a ) CoF; ( b ) Relative wear rate (in relation to their corresponding RT wear). Values are labeled as per hBN concentration, matrix material, and fabrication method [ 80 , 81 , 82 , 83 , 84 , 85 , 86 ]. …”