Microstructure and tribological behavior of amorphous and crystalline composite coatings using laser melting

Four composite coatings were fabricated by laser melting. Amorphous phase appeared in the Fe43.2Ni28.8B19.2Si4.8Nb4 and Fe43.2Co14.4Ni14.4B19.2Si4.8Nb4 coatings but not in the Fe30Co30Ni15B17Si8 and Fe39Ni36Mo2B18Si5 coatings. The growth of crystalline grain in the coatings was suppressed greatly due to the large cooling rates caused by fast laser scanning. But the crystallization in the coatings cannot be avoided completely and an amorphous and crystalline composite coating was formed in melted zone. Amorphous phase can increase the hardness of coatings greatly and the highest hardness is related to the amount of amorphous phase in the coatings. The amorphous and crystalline composite coatings exhibit excellent performance of abrasion.