Poškozování difuzních povlaků na turbínových lopatkách

Damage of Diffusion Coatings on Turbine Blades

conference paper

en

Nickel- and cobalt-based superalloys have been developed and are used in the hot sections of gas turbines in order to meet complex high-temperature phenomena. The gas temperature in modern engines exceeds 1650 C in the turbine section and its cooled parts reach temperatures as high as 1200 C. During operation, the structural materials degrade by fatigue, creep, oxidation, corrosion and erosive wear. Protective coatings provide barriers between the alloys and outer environment and, in particular, they enhance a resistance to oxidation and hot corrosion. The metallic coatings can be divided into two categories: diffusion and overlay coatings. Diffusion aluminide coatings (DAC) are based on the intermetallic compound beta-NiAl that forms under the influence of the substrate. Although DAC have been enjoying wide application, they have a limitation which arises from no deliberate changes of their properties to meet requirements of specific service conditions. This article is focused on a detection of damage that formed in the diffusion coatings on first stage turbine blades after two different short-term overheating events. Motivation for this study came from demands for an extension of our knowledge of degradation mechanisms. A possibility of a non-destructive assessment of the damage level using suitable damage parameters is also briefly described

Niklové a kobaltové superslitiny byly vyvinuty pro použití ve vysokoteplotních částech turbín.Teplota plynu v moderních motorech překračuje 1650 C, v chlazených částech se jedná o teploty až 1200 C. Během provozu dochází k degradaci částí v důsledku únavy, tečení, koroze a oxidace a erozivního opotřebení. Ochranné povlaky poskytují bariéru mezi slitinou a vnějším prostředím; jejich hlavním přínosem je zvyšení odolnosti vůči oxidaci a korozi . Kovové povlaky mohou být rozděleny do dvou kategorií: difuzní a krycí povlaky. Difúzní aluminidového povlaky (DAC) jsou založeny na intermetalické fázi beta-NiAl, která se tvoří za vlivu substrátu. Článek je zaměřen na kvantifikaci poškození difúzních povlaků, které vzniklo na lopatkách turbín prvního stupně po dvou různých krátkodobých přehřátích. Motivace pro tuto studii vychází z požadavků na rozšíření znalostí o degradačních mechanismech.Diskutována je rovněž možnost nedestruktivního vyhodnocení poškození pomocí vhodných fyzikálních parametrů.

Nickel- and cobalt-based superalloys have been developed and are used in the hot sections of gas turbines in order to meet complex high-temperature phenomena. The gas temperature in modern engines exceeds 1650 C in the turbine section and its cooled parts reach temperatures as high as 1200 C. During operation, the structural materials degrade by fatigue, creep, oxidation, corrosion and erosive wear. Protective coatings provide barriers between the alloys and outer environment and, in particular, they enhance a resistance to oxidation and hot corrosion. The metallic coatings can be divided into two categories: diffusion and overlay coatings. Diffusion aluminide coatings (DAC) are based on the intermetallic compound beta-NiAl that forms under the influence of the substrate. Although DAC have been enjoying wide application, they have a limitation which arises from no deliberate changes of their properties to meet requirements of specific service conditions. This article is focused on a detection of damage that formed in the diffusion coatings on first stage turbine blades after two different short-term overheating events. Motivation for this study came from demands for an extension of our knowledge of degradation mechanisms. A possibility of a non-destructive assessment of the damage level using suitable damage parameters is also briefly described

difúzní povlaky, přehřátí, degradační parametr, tečení, letecký motor

Diffusion aluminide coating, overheating, degradation parameter, creep, aircraft engine

2011

18.05.2011

Tanger sro

Ostrava

978-80-87294-24-6

METAL 2011 Conference Proceedings

1

840–846

7