灰铸铁表面激光熔覆NiCuFeBSi合金层中碳扩散形式研究

Carbon Diffusions in the NiCuFeBSi Alloy Layer Treated by Laser Cladding on Gray Cast Iron

摘要:

在HT250铸铁基体上采用Nd:YAG激光器制备了NiCuFeBSi合金熔覆层，研究了熔覆层、半熔化区、热影响区部位的碳元素扩散分布形式。结果表明，在熔覆层内部碳元素以细片石墨、固溶于NiCu固溶体内的C原子以及以CO气体形式存在；而在半熔化区碳元素则以与Fe形成的介稳定相Fe3C和微晶石墨球形式存在；在基体热影响区，碳原子从石墨内向周围扩散，在极大冷速作用下，碳原子大量过饱和固溶于针状马氏体组织内，且随着距结合界面距离的增加，马氏体含量逐渐降低，基体石墨熔解程度减弱，呈完整细片状

Abstract:

A NiCuFeBSi alloy layer was fabricated by laser cladding on HT250 substrate through a Nd:YAG laser. And each carbon structure in the cladding layer, semi-melt zone and heat affected zone (HAZ) was investigated. Results show that carbon distributes in the cladding layers in the form of graphite, CO and C atom solid soluted in [Ni,Cu]. However, carbon distributing in the semi-melt zone are in the form of Fe3C and micro graphite pebble. And in the HAZ, carbon diffuses around graphite and solid solutes in the acicular martensite due to the extremely high cooling rate of molten pool. Moreover, with increasing of the distance to the bonding interface, the content of martensite decreases gradually. Graphite in the substrate fuses less and keeps to be flake