Hafnium effects and protective coating performance

Conference · · TMS (The Metallurgical Society) Paper Selection; (USA)

OSTI ID:5449575

Smeggil, J G; Bornstein, N S ^[1]

---

1. United Technologies Research Center, East Hartford, CT (USA)

Protective coatings are commonly used to extend the useful lifetimes of superalloys exposed to aggressive atmospheres at elevated temperatures. The performance of these coatings on such hardware can be influenced by the chemistry of the superalloy substrates. Such performance-related effects can be either beneficial or detrimental to coating performance. Hafnium, an important element for oxide scale adherence effects, is occasionally added at low levels (approximately 0.01 wt. %) to superalloy compositions. However, such a level may not be the optimum level for protective coating performance. Furthermore, it would well be expected that the substrate hafnium level needed for optimum pack aluminide coating performance would significantly differ from that required for optimum overlay coating performance. In the former case, the hafnium level in the coating derives completely by diffusion effects involving the substrate. However, in the case of thicker overlay coatings, hafnium levels derived by diffusion from the substrate may be insufficient for optimal performance, hence requiring hafnium additions to the coating composition itself. The results of a study to examine the effects of hafnium derived from a nickel-based superalloy for aluminide coatings and of hafnium added to overlay coating compositions on oxidation and hot corrosion resistance are presented.

• OSTI ID: 5449575
• Report Number(s): CONF-840909--
• Conference Information: Journal Name: TMS (The Metallurgical Society) Paper Selection; (USA) Journal Volume: 56
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ADHESION
ALLOYS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
COATINGS
CORROSION RESISTANCE
DEPOSITS
DIFFUSION
ELEMENTS
HAFNIUM
HAFNIUM ADDITIONS
HAFNIUM ALLOYS
METALLURGICAL EFFECTS
METALS
NICKEL ALLOYS
NICKEL BASE ALLOYS
OPTIMIZATION
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE TESTING
PROTECTIVE COATINGS
SERVICE LIFE
TESTING
TRANSITION ELEMENTS