Crystallization behavior of nanometer-sized Al2O3 composite coatings prepared by electroless deposition

Nanometer-sized AL(2)O(3) particle-reinforced nickel-phosphorus matrix composite (Ni-P-AL(2)O(3)) coatings were prepared by electroless deposition. Particles were found to distribute homogeneously in Ni-P-AL(2)O(3) coatings by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). It was found that the crystallization temperature of the composite coating decreased from the results of differential scanning calorimetry (DSC-7) and X-ray diftractometry. The activation energy and Avrami exponent of crystallization were lowered due to co-deposited particles in composite coatings. Nickel phosphide (Ni3P) precipitated after heat treatment at 230 degreesC for 24 It in Ni-P-AL(2)O(3) coatings, while Ni-P coatings kept amorphous under such condition. Because of the existence of nanometersized particles, microhardness of the composite coatings greatly increased. With heat treatment, microhardness values of composite coatings as high as HV(50)1150 were produced. (C) 2004 Elsevier B.V. All rights reserved.