Structure and oxidation behavior of Si–Y co-deposition coatings on an Nb silicide based ultrahigh temperature alloy prepared by pack cementation technique

2009 ◽  
Vol 204 (3) ◽  
pp. 313-318 ◽  
Author(s):  
Xiaodong Tian ◽  
Xiping Guo
Keyword(s):  
Oxidation Behavior ◽  
Pack Cementation ◽  
Ultrahigh Temperature

Si-B Co-Deposition Coatings on an Nb Silicide Based Ultrahigh Temperature Alloy Prepared by Pack Cementation Technique

2011 ◽  
Vol 686 ◽  
pp. 630-636 ◽  
Author(s):  
Yu Zhang ◽  
Xi Ping Guo
Keyword(s):  
Oxidation Resistance ◽  
Layer Structure ◽  
Pack Cementation ◽  
Microstructural Characteristics ◽  
Triple Layer ◽  
Ultrahigh Temperature

In order to improve the oxidation resistance of silicide coatings on an Nb silicide based alloy, Si-B co-deposition coatings were prepared at 1150°C for 8 h by using pack mixtures containing different amounts of B powders. The microstructural characteristics of the coatings were studied. The results showed that all coatings had a triple-layer structure. The middle layers of all coatings were composed of (Nb,X)Si2 (X represents Ti, Cr and Hf elements) and the inner layers of all coatings were composed of (Nb,X)5Si3, but the outer layers of the coatings had different phase constituents and morphologies when the amount of B powders in the pack mixture changed. When the amount of B powders in the pack mixture ranged from 0.5 wt% to 12 wt%, the outer layers were composed of (Nb,X)B2­, with a few CrB2 particles. When the amount of B powders in the pack mixture was in the range of 0.05~0.1 wt%, the outer layers were composed of (Nb,X)B2. However, when the amount of B powders in the pack mixture was in the range of 0.02~0.03 wt%, the outer layers were composed of (Nb,X)Si2, with needle-like (Nb,X)B2 particles dispersed in it.

Phase Constitution and Oxidation Resistance of B2 (Ir, Co)Al

2002 ◽  
Vol 753 ◽  
Author(s):  
Hideki Hosoda ◽  
Hiroshi Noma ◽  
Kenji Wakashima
Keyword(s):  
Oxidation Resistance ◽  
Oxidation Behavior ◽  
Hot Forging ◽  
Isothermal Oxidation ◽  
Oxidation Products ◽  
Phase Constitution ◽  
Temperature Oxidation ◽  
Arc Melting ◽  
Oxidation Resistant ◽  
Ultrahigh Temperature

ABSTRACTB2 iridium aluminide (IrAl) is hopeful for use as an ultrahigh temperature oxidation resistant coating above 1600K. In this study, the effect of Co substitution for Ir on phase constitution, hardness and oxidation behavior was studied for IrAl alloys. Alloys of (Ir, Co)-50mol%Al with various Co contents were fabricated by Ar-arc melting followed by hot-forging at 1773K. Oxidation behavior was evaluated using thermogravimetry (TG) in Ar-67%O2 up to 1823K. XRD and SEM were also carried out for alloy characterization. It was found that a continuous B2 solid solution (Ir,Co)Al is formed between IrAl and CoAl. Depending on the Co concentration, the oxidation products identified after heating to 1873K in Ar-67%O2 were Ir, IrO2 and A2O3 and/or Co2AlO4. Thin and continuous Al2O3 layers were observed after isothermal oxidation at 1673K when Co content is more than 20mol%Co. In this case, the weight change by isothermal oxidation at 1673K becomes higher with decreasing Co content. The (Ir,Co)Al alloys containing 20–40mol%Co exhibit higher oxidation resistance than CoAl and IrAl, and thus oxidation resistance of CoAl is improved by Ir addition.

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