Effects of carbon nanotubes on hardness and internal stress in Ni-P coatings ..

摘要

Nickel-phosphorus carbon nanotube (CNT) composite coatings were prepared via brush electroplating. The CNTs were added in amounts of 0, 0.5, 1.0 and 2.0 g L~(-1). Half samples of these coatings were heated at 400°C for 1 h to obtain crystalline Ni-P CNT composite coatings. The hardness and internal stress of two kinds of composite coatings were studied. The results showed that the addition of CNTs improves the microhardness of crystalline Ni-P coatings; the higher the added CNT, the greater increase in microhardness. However, the effects are completely different for amorphous coatings. Heat treatment greatly increased the microhardness of amorphous Ni-P platings, but the microhardness of Ni-P based CNT composite coatings only slightly increased. The microhardness of the crystalline Ni-P based CNT composite coatings was lower than that of the crystalline Ni-P platings and was not insensitive to the changes in the added amounts of CNTs. The addition of CNTs significantly reduced the microscopic internal pressure stress of crystalline coatings; the higher the added CNT, the lower the microscopic internal pressure stress.