Ni基合金/45#钢宽、窄带熔覆Co基合金的组织

利用 5kWCO2 激光器在Ni基铸造高温合金 4 5 #钢基体上宽带、窄带激光熔覆了H¨ogan¨as钴基合金 ,制备了无缺陷的涂层。用金相显微镜、扫描电镜和X射线衍射仪对比分析了熔覆层的显微组织特征和相结构。结果显示 ,熔覆层均为由初生相γ Co枝晶和γ Co +Cr2 3C6 共晶组成。宽带熔覆层界面为垂直于界面生长 ,窄带熔覆层界面结晶方向受热流控制 ,为多方向结晶。 4 5 #钢熔覆层界面具有明显的白亮过渡层且宽带熔覆比窄带宽 ;Ni基合金熔覆层界面区很宽且不规则 ,无白亮色过渡层。沿熔覆层中心线的纵截面取样可见平行生长的枝晶

Microstructure of Wide/Narrow Band Beam Laser Cladding Co-based Alloy on Ni Base Superalloy/45# Steel

HGganAas Co based alloy coatings have been produced by using a 5 kW CO 2 laser with wide/narrow band beam on Ni based superalloy/45 # steel. Cross-section or vertical-section of such coatings have been examined to reveal their microstructure using phase-contrast microscope, scanning electronic microscope and X-ray diffraction instrument. The results showed the primary phase γ-Co dendrite and γ-Co+Cr 23C 6 eutectic Co-existed in the coating. Dendrite grew perpendicularly to the interface in wide band laser beam coatings and more direction in narrow band laser coatings because of heat flux. There was a white thin layer of planar crystallizing at the interface of 45 # steel substrate, and the width of the broad beam coatings was wider than that of narrow beam coatings. It was irregular and no sign of white thin layer at interface region of Ni-based alloy substrate. The results also showed that dendrite grew paralleling to laser scanning direction near top surface of the central line coatings (vertical section).