Laser Cladding of Nanocrystalline Alloy of Cast Iron with Niobium and Boron Addition
Felipe Amélio de Lucena1; Claudemiro Bolfarini2; Cláudio Shyinti Kiminami2; Conrado Ramos Moreira Afonso2
1 Instituto Federal de São Paulo; 2 Universidade Federal de São Carlos
doi:10.20906/CPS/COB-2015-1999
Resumo
Amorphous and nanocrystalline Fe-based alloys present excellent properties, such as high hardness and wear resistance, with cooling rates of 103 to 105 K/s. Thus, this study aims obtain nanocrystalline or metastable structure through rapid solidification (RS) of white cast iron with B and Nb additions, resulting in composition (Fe65Cr17Mo2C14Si2)88B8Nb4 (%at.), and the overspray powder was used to produce coatings of ferrous metallic alloys on AISI 1020 mild steel substrate by laser cladding of the pre-placed powders. The ferrous alloy was processed through Melt-Spinning, the Discovery® Plasma copper mold casting (CMC) and Spray Forming (SF) obtaining ribbons (40 µm thick), plates (1.0 and 2.0 mm) (CMC) and powders (20 to 180 µm) of (Fe65Cr17Mo2C14Si2)88B8Nb4 (%at) alloy. Different laser parameters, power (200, 400 and 600 W), scanning speeds (10.0-150.0 mm/s), were tested using a Yb fiber laser (2 kW) and the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and measurements of Vickers microhardness. The characterization showed amorphous ribbons, nanocrystalline powders, plates (mm) and clad tracks with nanocrystalline phases: α-Fe, ɣ-Fe, Cr7C3, FeNbB e Fe2B. Laser clad coatings showed Vickers microhardness ranging 660-1480 HV depending on laser parameters and respective power density (W/mm2).
Palavras-chave: Cast Iron; Spray forming; Rapid Solidification; Characterization; Laser Cadding