Cr,Al颗粒尺寸对Ni-Cr-Al复合镀层氧化行为的影响

SIZE EFFECT OF Cr AND Al PARTICLE ON THE OXIDATION BEHAVIOR OF ELECTRODEPOSITED Ni-Cr-Al COMPOSITE COATINGS

分别用纳米颗粒Cr(平均尺寸62 nm),Al(平均尺寸85nm)和微米颗粒Cr和Al(平均尺寸3μm)复合电沉积制备Ni-11Cr-3Al纳米复合镀层(ENC)和Ni-11Cr-7Al微米复国镀层(EMC)。纳米颗粒的复合使ENC Ni-11Cr-3Al比EMC Ni-11Cr-7Al的颗粒分布更加均匀,颗粒间距减小近25倍。900℃,24h恒温氧化实验表明,ENC Ni-11Cr-3Al与EMC Ni-11Cr-7Al相比氧化速率显著降低。这是由于其快速形成一层连续、致密的Cr_2O_3膜,进而促进其下Al_2O_3膜的快速形成所致。

Two electrodeposited Ni matrix composite coatings were prepared; one was Ni-11Cr-3A1 （by mass%） prepared using nano-sized particles of Cr and A1 and the other was Ni-llCr-7A1 composite prepared using micron-sized particles of Cr and A1. Compared with the electrodeposited micron-composite （EMC） Ni- llCr-7A1, the electrodeposited nanocomposite （ENC） Ni-llCr-3A1 exhibited much homogeneous distribution of Cr and A1 particles, because of an approximately 25-fold decrease in interparticle spacing. The significantly shorter interparticle spacing allowed the ENC Ni-llCr-3A1 to grow a continuous Cr203 layer first and then an A1203 layer underneath during a very short stage of oxidation. This is the fundamental reason for the result that the ENC, although it had a lower content of A1, was oxidized slower than the EMC Ni-llCr-7A1 during oxidation in air at 900 ℃. The size effect of the Cr electrodeDosited Ni-Cr-A1 composite coatings is discussed in detail.