Tribological characteristics and tribo-chemical mechanisms of Al–Mg–Ti–B coatings under water–glycol lubrication

Experimental and Theoretical Study of Ultra-Hard AlMgB14-TiB2 Composites: Structure, Hardness and Self-Lubricity

“…Currently, AlMgB 14 -based materials (BAMs) are of great interest due to their unique physical and mechanical properties. BAMs have an extremely low friction coefficient (COF, ~0.08–0.02) [ 1 , 2 , 3 ], a high hardness, with value reaching 32 GPa [ 4 ], a coefficient of thermal expansion (CTE) close to steel (11.7 × 10 −6 K −1 ) [ 5 ], and a high thermal and chemical stability. Although AlMgB 14 single crystals were first obtained in 1970 by Matkovich and Economy [ 6 ], polycrystalline materials based on AlMgB 14 have been actively studied since 2000 in the Ames Laboratory (USA) [ 2 , 3 , 4 ].…”

“…Although AlMgB 14 single crystals were first obtained in 1970 by Matkovich and Economy [ 6 ], polycrystalline materials based on AlMgB 14 have been actively studied since 2000 in the Ames Laboratory (USA) [ 2 , 3 , 4 ]. First, the scientists of [ 4 ] found that the addition of TiB 2 increases the hardness of the AlMgB 14 -TiB 2 composite to 40–46 GPa, and then the studies of the tribological characteristics showed that the friction coefficient of the AlMgB 14 coating in dry conditions can reach 0.05 [ 3 ], while the friction coefficient of the AlMgB 14 -TiB 2 coating in a water-glycol lubricant can reach values of 0.02 [ 1 ]. Due to the unique combination of these properties, AlMgB 14 has attracted great attention as a wear-resistant material in the friction units of critical machine parts.…”

“…Tribological analysis showed that the extremely low friction coefficient in dry conditions and water-glycol lubricants is associated with the release of B 2 O 3 and B(OH) 3 particles [ 1 , 2 , 3 ] during the friction. Studies of the tribological characteristics of AlMgB 14 -TiB 2 composites in dry conditions [ 7 ] revealed that the COF of AlMgB 14 -30 wt% TiB 2 at room temperature varies in the range from 0.45 to 0.65 against the SiC counterface and decreases significantly to 0.2 at 800 °C.…”

“…These particles lubricate the surface, reducing the COF and wear, respectively. They are released either in the rigid metal matrix [ 8 , 9 ], or when using certain lubricants [ 1 , 2 , 3 ], or when the surface is heated [ 7 ]. At the same time, the question of the mechanism of the self-lubrication of bulk composites AlMgB 14 -TiB 2 in dry conditions at room temperature remains open.…”

On the Structure and Properties of AlMgB14-TiB2 Composites Obtained from SHS Powders by Spark Plasma Sintering

“…First of all, it is a combination of high hardness and low friction coefficient. Since that moment, scientists from different countries have been actively investigating AlMgB 14 materials and composite materials based on them: in particular, methods of fabricating bulk specimens [ 1 , 2 , 3 , 4 ], methods of obtaining coatings [ 5 , 6 ], formation [ 4 , 7 ] and decomposition [ 8 ] mechanisms, tribological characteristics of AlMgB 14 -based materials in dry conditions [ 7 , 9 , 10 ] and in various lubricants [ 11 , 12 ], and mechanical properties [ 1 , 2 , 3 , 4 , 7 , 8 ]. Over the past two decades, many methods have been reported for the production of AlMgB 14 -based materials, but these can be divided into two groups.…”