Microstructure and Oxidation Resistance of an Aluminide Coating on the Nickel Based Superalloy Mar M247 Deposited by the CVD Aluminizing Process

Abstract

An investigation was conducted to synthesize βNiAl coating on the nickel based superalloy Mar M247 in a chemical vapor deposition process (CVD). The low activity process of aluminizing was carried out for 8 hours at the temperature 1050• C. Surface morphology and cross-section microstructure of the diffusion coating were studied and compared by using an optical microscope, a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy and an X-ray diffractometer. It was found that aluminide coating with the thickness of 37 µm consisted of two layers: an outer one and the inner interdiffusion one. The outer layer consists of single phase βNiAl. The inner one, consisted of βNiAl phase and carbides: MC and M 23 C 6 types which were originally present in the substrate. Cyclic oxidation test was performed at 1000• C for 1000h in the air atmosphere. The aluminized samples exhibited a small mass increase and the α-Al 2 O 3 oxide formed during oxidation test had a good adherence to the coating. The decrease of aluminum content in the coating with the prolongation of the oxidation time and the phase transformation of βNiAl to γ' Ni 3 Al and to γNi solid solution were observed. The samples without the coating showed a strong mass decrease in comparison to the coated samples.Keywords: Mar M247 Ni-base superalloy, CVD method, aluminide coating, oxidation resistance Niskoaktywny proces aluminiowania prowadzono w temperaturze 1050• C i w czasie 8 h. Badania mikrostruktury na przekroju oraz powierzchni warstwy dyfuzyjnej prowadzono za pomocą mikroskopu optycznego oraz skaningowego mikroskopu elektronowego wyposażonego w detektor EDS. Skład fazowy określano metodą rentgenowskiej analizy fazowej. Uzyskano warstwę aluminidkową o grubości 37 µm składająca się z dwóch stref: zewnętrznej oraz wewnętrznej (dyfuzyjnej). Strefa zewnętrzna składa się z fazy βNiAl. Natomiast wewnętrzna -z fazy βNiAl oraz węglików typu MC oraz M 23 C 6 . Badania cyklicznego utleniania prowadzono w temperaturze 1000• C i w czasie 1000 h w atmosferze powietrza. Podczas utleniania warstwy aluminidkowej powstaje tlenek α-Al 2 O 3 o dobrej przyczepności do warstwy dyfuzyjnej. Zwiększenie czasu utleniania od o do 1000 h powoduje zmniejszenie zawartości aluminium oraz przemianę fazową β-NiAl do γ'-Ni 3 Al i do stałego roztworu γ-Ni. Materiał bez warstwy aluminidkowej charakteryzuje się większą szybkością utleniania w porównaniu do materiału z warstwą aluminidkową.

Nanoparticles in zirconium-doped aluminide coatings

“…The aluminide coating was deposited using the CVD equipment BPXPR0325S manufactured by IonBond company [1,2,8,11,12,17]. The aluminizing process consisted of the following stages: I-heating from the room temperature up to 900 1C; II-aluminizing at 900 1C for 20 min; III-heating from 900 1C to 1020 1C; IV-aluminizing at 1020 1C for 5 min; V-aluminizing and zirconizing at 1020 1C for 4 min; VI-aluminizing at 1020 1C for 10 min; VII-cooling samples with the furnace.…”

“…It can be achieved by the increase of the volume of the air flowing through the turbine as well as by the increase of the temperature at its hot stage. The increase of the temperature of gases at the turbine inlet in modern engines depends on the efficient cooling systems of turbine blades and the usage of nickel or cobalt superalloys with protective thermal barrier coatings (TBC) [1][2][3][4][5][6]. The improvement of engine efficiency by the increase of turbine inlet temperature implicates the use of different types of protecting coatings including aluminide and MeCrAlY multicomponent ones.…”

Microstructure and oxidation behaviour investigation of rhodium modified aluminide coating deposited on CMSX 4 superalloy

“…The rhodium layer of 0.5-μm thick was deposited on CMSX 4 superalloy using the electroplating method. The rhodium coated superalloy was aluminized by the CVD method (Romanowska et al, 2013;Zielińska et al, 2013;Romanowska et al, 2015;Zagula-Yavorska et al, 2015). The chemical composition of the superalloy was as follows: 61.7% wt.…”

SEM/TEM Investigation of Aluminide Coating Co-Doped with Pt and Hf Deposited on Inconel 625

“…In this case the bond coating also serves to ensure top coating adhesion, mitigates thermal mismatch stresses with the substrate and is not solely for oxidation protection. The compatibility between the thermally grown oxide (TGO) scale (comprising of Al 2 O 3 and other oxides) forms during oxidation and TBCs plays a crucial role in governing coatings durability [ 3 ]. Leckie et al [ 4 ] studied the thermochemical compatibility between alumina (TGO) and Gd 2 Zr 2 O 7 .…”