激光表面熔覆制备ODS Ni基高温合金涂层的凝固组织

Microstructure of ODS Superalloy Coating Produced by Laser Surface Cladding

摘要:

采用横流CO2激光，在Ni基高温合金表面制备了纳米Al2O3弥散强化(ODS)Ni基合金熔覆层。利用光学显微镜、扫描电镜及EDS附件分析了熔覆层的组织结构。结果表明：界面晶粒的生长方向为垂直于界面的“外延式”生长；加入纳米Al2O3，界面的生长形态发生变化，由细长的柱状树枝晶转变为较短的树枝晶；纳米Al2O3含量增大至1％时整个断面获得等轴枝晶组织；纳米Al2O3作为异质形核的核心，细化了组织。

Abstract:

Nano-Al2O3 dispersion strengthened Ni-based alloy coatings produced by crosscurrent CO2 laser on Ni-based superalloy are introduced. Cross-section of the coatings have been examined to reveal their microstructure, using optical microscope and SEM (including EDS microanalysis). The results show that rapid directional solidification of epitaxy is found at the interface where the growth direction is perpendicular to the bottom of melting pool. The size of columnar dendrite is decreased by adding Al2O3 nanocrystalline to the powder. A novel microstructure of equiaxed solidification has been observed with the increasing a mount of Al2O3 to 1% (in weight). Fine and equiaxed microstructure has been obtained for the nanocrystalline Al2O3 acting as new nucleation site of the melting pool.