TY - JOUR
T1 - Structure of Al-modified silicide coatings on an Nb-based ultrahigh temperature alloy prepared by pack cementation techniques
AU - Tian, Xiaodong
AU - Guo, Xiping
PY - 2009/1/25
Y1 - 2009/1/25
N2 - In order to prepare Al-modified silicide coatings on an Nb-based ultrahigh temperature alloy, both a two-stage pack cementation technique and a co-deposition pack cementation technique were employed. The two-stage process included siliconizing a specimen at 1150 °C for 4 h followed by aluminizing it at 800-1000 °C for 4 h. The coating prepared by pack siliconization was composed of a thick (Nb,X)Si2 (X represents Ti, Cr and Hf elements) outer layer and a thin (Nb,X)5Si3 transitional layer; after the siliconized specimens were aluminized at or above 860 °C, a (Nb,Ti)3Si5Al2 phase developed at the surface of the coating, and furthermore, when aluminizing was carried out at 860 °C, a new (Nb,Ti)2Al layer formed in the coating between the (Nb,X)5Si3 layer and the substrate, but when aluminizing was performed at 900-1000 °C, the new layer formed was (Nb,Ti)Al3. The co-deposition process was carried out by co-depositing Si and Al on specimens at 1000-1150 °C for 8 h under different pack compositions, and it was found that the structure of co-deposition coatings was more evidently affected by co-deposition temperature than pack composition. An Al-modified silicide coating with an outer layer composed of (Nb,Ti)3Si5Al2, (Nb,X)Si2 and (Nb,Ti)Al3 was obtained by co-depositing Si and Al at 1050 °C.
AB - In order to prepare Al-modified silicide coatings on an Nb-based ultrahigh temperature alloy, both a two-stage pack cementation technique and a co-deposition pack cementation technique were employed. The two-stage process included siliconizing a specimen at 1150 °C for 4 h followed by aluminizing it at 800-1000 °C for 4 h. The coating prepared by pack siliconization was composed of a thick (Nb,X)Si2 (X represents Ti, Cr and Hf elements) outer layer and a thin (Nb,X)5Si3 transitional layer; after the siliconized specimens were aluminized at or above 860 °C, a (Nb,Ti)3Si5Al2 phase developed at the surface of the coating, and furthermore, when aluminizing was carried out at 860 °C, a new (Nb,Ti)2Al layer formed in the coating between the (Nb,X)5Si3 layer and the substrate, but when aluminizing was performed at 900-1000 °C, the new layer formed was (Nb,Ti)Al3. The co-deposition process was carried out by co-depositing Si and Al on specimens at 1000-1150 °C for 8 h under different pack compositions, and it was found that the structure of co-deposition coatings was more evidently affected by co-deposition temperature than pack composition. An Al-modified silicide coating with an outer layer composed of (Nb,Ti)3Si5Al2, (Nb,X)Si2 and (Nb,Ti)Al3 was obtained by co-depositing Si and Al at 1050 °C.
KW - Al-modified silicide coating
KW - Nb-based ultrahigh temperature alloy
KW - Pack cementation
UR - http://www.scopus.com/inward/record.url?scp=58149483710&partnerID=8YFLogxK
U2 - 10.1016/j.surfcoat.2008.10.018
DO - 10.1016/j.surfcoat.2008.10.018
M3 - 文章
AN - SCOPUS:58149483710
SN - 0257-8972
VL - 203
SP - 1161
EP - 1166
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
IS - 9
ER -