渗铝时间对PtAl涂层高温抗氧化行为的影响

Effect of Aluminization Time on the High Temperature Oxidation Behavior of PtAl Coating

以镍基高温合金GH586为基体材料,采用电镀Pt和固体粉末包埋渗铝的方法在其表面制备PtAl涂层。采用X射线衍射(XRD)、扫描电镜(SEM)对不同渗铝时间下PtAl涂层的高温氧化过程中各阶段的物相结构及微观组织变化进行表征及分析。研究表明,在高温氧化过程中,随着渗铝时间的增加,涂层中β-NiAl相转变为γ'-Ni_3Al相的几率越小,迅速生成Al_2O_3膜的时间越短,形成起扩散障作用的Cr、W等元素富集区的厚度越大,从而大大提高了镍基合金的抗氧化性。渗铝3 h的PtAl涂层具有最优的抗氧化性能,其氧化速率常数k_(3h)=1.17×10^(-6)。

PtAl coating was prepared by plating platinum on GH586 Ni-base superalloys surface and solid-aluminizing for different time in powder pack.Through X-ray diffraction（XRD） and scanning electron microscopy（SEM）,the variation of phase structure and microstructure of PtAl coating during the high temperature oxidation were determined and discussed.The results showed that during the high temperature oxidation,the probability of β-NiAl phase transformed into γ＇-Ni3A1 phase decreased with the increase of aluminizing time.As a result,the formation time of Al2O3 film was shortened,leading to the increase of the thickness of element（Cr,W etc.as the diffusion barrier effect） enrichment region.These greatly improved the inoxidizability of Ni-base alloys.It is therefore concluded that PtAl coating,produced by aluminizing for 3 hours,possesses the optimal inoxidizability and the oxidation rate constant k_3h=1.17×10^-6.