在镍基单晶高温合金上采用复合电镀的方法沉积Pt-Zr复合镀层,随后通过气相渗铝的方法,获得Zr改性的PtAl₂+(Ni, Pt)Al双相涂层,该涂层分为3层：外层由PtAl₂颗粒弥散分布在β-(Ni, Pt)Al中的双相区组成,中间层为β-(Ni, Pt)Al及少量Cr的析出物,内层为互扩散区(IDZ)。其中,Zr元素主要固溶在外层双相区以及中间层β-(Ni, Pt)Al中。分别对Zr改性和普通PtAl₂+(Ni, Pt)Al双相涂层在850 ℃下Na₂SO₄/NaCl (75:25,质量比)混合盐中进行热腐蚀实验,结果表明,因Zr元素具有固定S和Cl的作用,可降低S和Cl在热腐蚀过程中的破坏性,故Zr改性PtAl₂+(Ni, Pt)Al双相涂层比普通PtAl₂+(Ni, Pt)Al双相涂层具有更好的抗热腐蚀性能。经过低真空预氧化处理后,普通PtAl₂+(Ni, Pt)Al双相涂层表面生成的Al₂O₃膜较薄,在后续热腐蚀过程中并不能有效抵挡混合盐的持续入侵,涂层长期抗热腐蚀性能与原始状态PtAl₂+(Ni, Pt)Al涂层样品接近。

Prior to practical service, hot-section components (e.g. airfoils and vanes) of a gas turbine engine are necessarily coated by a protective metallic coating (such as aluminide diffusion coating, modified aluminide coating and MCrAlY overlay etc.) to resist high temperature oxidation and hot corrosion. Among the modified aluminide coatings, the coating with Pt-modification has attracted great attention and is widely used in applications requiring high reliability and extended service life since it possesses superior oxidation/corrosion resistance at high temperature. The presence of Pt in aluminide coating is favorable for increasing bonding strength of oxide scale, enlarging phase region of β-NiAl and confining detrimental effect of sulphur etc. Although Pt-modification has exhibited visible benefits for acquiring better high-temperature performance, it is far from satisfaction to develop an ideal aluminide diffusion coating. Reactive elements such as Y, Hf, Zr or their oxides have been employed to modify the nickel aluminide coating system, with an aim to further improve scale adhesion and promote exclusive formation of α-Al₂O₃ simultaneously. In this work, a Zr-doped PtAl₂+(Ni, Pt)Al dual-phase aluminide coating was prepared on a Ni-based single crystal superalloy by co-deposition of Pt-Zr through electroplating and subsequent aluminization treatments. The coating was mainly composed of three layers: the outmost layer consisted of double phases with PtAl₂ particles dispersed in β-(Ni, Pt)Al domain, while the interlayer comprised β-(Ni, Pt)Al with small amount of Cr-precipitates, and the bottom layer was an inter-diffusion zone (IDZ). Zirconium was mainly distributed inside β-(Ni, Pt)Al solid solution in both the outmost layer and the interlayer. Compared with normal PtAl₂+(Ni, Pt)Al dual-phase coating, the hot corrosion behavior of the Zr-doped PtAl₂+(Ni, Pt)Al coating was assessed in a salt mixture of Na₂SO₄/NaCl (75:25, mass ratio) at 850 ℃ in static air. The results indicated that the Zr-doped PtAl₂+(Ni, Pt)Al dual-phase coating exhibited superior hot corrosion resistance since Zr was confirmed able to capture and fix S and Cl to diminish their detrimental effects. Meanwhile, a pre-oxidation treatment did not effectively improve the overall hot corrosion resistance of normal PtAl₂+(Ni, Pt)Al coating because the thin alumina scale formed during pre-oxidation was unable to prohibit the sustained inward-invasion of the mixed salt.