Thick amorphous coating of Fe-based alloy by laser clad

There was substantial interest in producing amorphous alloy (a-alloy) layer on bulk crystalline substrates using laser surface amorphization techniques, in view of the attractive mechanical, physical and chemical properties of a-alloys. However, because of the necessity of high cooling rates above 106 K/s for a-alloy formation, the resulting layer was limited to less than 50 μm. With the discovery of a series of new bulk a-alloys with complex multicomponent chemistry and excellent glass formation ability (GFA) from the early 1990s, bright prospects were opened up for synthesis of thick a-alloy coatings with large GFA. The present paper proposed an exploratory study on multicomponent Fe-based alloy surface amorphization by laser cladding using a high energy CO2 laser. A new and original Fe-based thick amorphous-alloy(a-alloy) coating was synthesized for the first time. The nature of the formation of the a-alloy was studied by using OM, EDS, XRD, TEM, HRTEM and DSC. The nominal composition of the a-alloy was Fe70Zr10Ni6Al4Si6 B4 (atom pct). A thick a-alloy coating of 0.74 mm maximum thickness was synthesized. The value of ΔT was 67K which shown the high thermal stability of the supercooled liquid. The cooling rate obtained by laser cladding is high enough to suppress the epitaxial growth of dendrites of the coating and to cause an a-alloy coating. The a-alloy coating revealed high microhardness of 940 - 980 HV0.2. The novel a-alloy was believed to have considerable potential as advanced engineering materials due to their advantageous properties and excellent processing capabilities.