Friction and wear behaviour of in-situ transformed Cf/Al2O3 composite under different lubrication conditions

• The Cf/Al2O3 composite is reinforced by in-situ transformed carbon fibres.
• New lubricant PAO+CNT has better anti- friction and wear effect.
• The wear resistance of 20% Cf/Al2O3 is at least 1.8 times higher than that of Al2O3.
• The wear rate of 20% Cf/Al2O3 under PAO+CNT is 1/3–2/3 of that under PAO.

In this paper,the friction, wear behaviour, and wear mechanisms of in-situ transformed carbon fibre toughened alumina ceramic matrix composite were investigated. The 20 vol% Cf/Al2O3 composites were fabricated by hot-press sintering in vacuum. Wear tests for 20 vol% Cf /Al2O3 composite, commercial Al2O3 ceramic and 40Cr steel were conducted using a cylinder on blocks wear tester under PAO oil and PAO+carbon nanotube (CNT) as lubricants and at applied loads of 220 N and 520 N as well. The results show that the frictional coefficient of these three materials at 520 N are lower than at 220 N and that 20 vol% Cf/Al2O3composite presents the lowest frictional coefficients. The wear resistance of 20 vol% Cf/Al2O3 is at least 10 times higher than 40Cr and 1.8 times higher than Al2O3 in both PAO oil and PAO+carbon nanotube(CNT) lubricants. The wear mechanisms of these three materials are different. 40Cr presents ploughing and local deformation and even tearing, Al2O3 shows spalling and grinding, and 20 vol% Cf/Al2O3 demonstrate slight spalling and shallow ploughing. These results show that in-situ transformed carbon fibres play a toughening role in Al2O3 ceramic and the PAO+CNT lubricant has better lubricative role than PAO oil.