TY - JOUR
T1 - Formation of Cr-modified silicide coatings on a Ti-Nb-Si based ultrahigh-temperature alloy by pack cementation process
AU - Qiao, Yanqiang
AU - Guo, Xiping
PY - 2010/10/1
Y1 - 2010/10/1
N2 - Cr-modified silicide coatings were prepared on a Ti-Nb-Si based ultrahigh temperature alloy by Si-Cr co-deposition at 1250 °C, 1350 °C and 1400 °C for 5-20 h respectively. It was found that both coating structure and phase constituents changed significantly with increase in the co-deposition temperature and holding time. The outer layers in all coatings prepared at 1250 °C for 5-20 h consisted of (Ti,X) 5 Si 3 (X represents Nb, Cr and Hf elements). (Ti,X) 5 Si 4 was found as the only phase constituent in the intermediate layers in both coatings prepared at 1250 °C for 5 and 10 h, but the intermediate layers in the coatings prepared at 1250 °C for 15 and 20 h were mainly composed of (Ti,X) 5 Si 3 phase that was derived from the decomposition of (Ti,X) 5 Si 4 phase. In the coating prepared at 1350 °C for 5 h, single (Ti,X) 5 Si 3 phase was found in its outmost layer, the same as that in the outer layers in the coatings prepared at 1250 °C; but in the coatings prepared at 1350 °C for 10-20 h, (Nb 1.95 Cr 1.05 )Cr 2 Si 3 ternary phase was found in the outmost layers besides (Ti,X) 5 Si 3 phase. In the coatings prepared at 1400 °C for 5-20 h, (Nb 1.95 Cr 1.05 )Cr 2 Si 3 ternary phase was the single phase constituent in their outmost layers. The phase transformation (Ti,X) 5 Si 4 → (Ti,X) 5 Si 3 + Si occurred in the intermediate layers of the coatings prepared at 1350 and 1400 °C with prolonging co-deposition time, similar to the situation in the coatings prepared at 1250 °C for 15 and 20 h, but this transformation has been speeded up by increase in the co-deposition temperature. The transitional layers were mainly composed of (Ti,X) 5 Si 3 phase in all coatings. The influence of co-deposition temperature on the diffusion ability of Cr atoms was greater than that of Si atoms in the Si-Cr co-deposition processes investigated. The growth of coatings obeyed inverse logarithmic laws at all three co-deposition temperatures. The Si-Cr co-deposition coating prepared at 1350 °C for 10 h showed a good oxidation resistance due to the formation of SiO 2 and Nb, Cr-doped TiO 2 scale after oxidation at 1250 °C for 10 h.
AB - Cr-modified silicide coatings were prepared on a Ti-Nb-Si based ultrahigh temperature alloy by Si-Cr co-deposition at 1250 °C, 1350 °C and 1400 °C for 5-20 h respectively. It was found that both coating structure and phase constituents changed significantly with increase in the co-deposition temperature and holding time. The outer layers in all coatings prepared at 1250 °C for 5-20 h consisted of (Ti,X) 5 Si 3 (X represents Nb, Cr and Hf elements). (Ti,X) 5 Si 4 was found as the only phase constituent in the intermediate layers in both coatings prepared at 1250 °C for 5 and 10 h, but the intermediate layers in the coatings prepared at 1250 °C for 15 and 20 h were mainly composed of (Ti,X) 5 Si 3 phase that was derived from the decomposition of (Ti,X) 5 Si 4 phase. In the coating prepared at 1350 °C for 5 h, single (Ti,X) 5 Si 3 phase was found in its outmost layer, the same as that in the outer layers in the coatings prepared at 1250 °C; but in the coatings prepared at 1350 °C for 10-20 h, (Nb 1.95 Cr 1.05 )Cr 2 Si 3 ternary phase was found in the outmost layers besides (Ti,X) 5 Si 3 phase. In the coatings prepared at 1400 °C for 5-20 h, (Nb 1.95 Cr 1.05 )Cr 2 Si 3 ternary phase was the single phase constituent in their outmost layers. The phase transformation (Ti,X) 5 Si 4 → (Ti,X) 5 Si 3 + Si occurred in the intermediate layers of the coatings prepared at 1350 and 1400 °C with prolonging co-deposition time, similar to the situation in the coatings prepared at 1250 °C for 15 and 20 h, but this transformation has been speeded up by increase in the co-deposition temperature. The transitional layers were mainly composed of (Ti,X) 5 Si 3 phase in all coatings. The influence of co-deposition temperature on the diffusion ability of Cr atoms was greater than that of Si atoms in the Si-Cr co-deposition processes investigated. The growth of coatings obeyed inverse logarithmic laws at all three co-deposition temperatures. The Si-Cr co-deposition coating prepared at 1350 °C for 10 h showed a good oxidation resistance due to the formation of SiO 2 and Nb, Cr-doped TiO 2 scale after oxidation at 1250 °C for 10 h.
KW - Coating structure
KW - Cr-modified silicide coating
KW - Pack cementation process
KW - Phase constituents
KW - Ti-Nb-Si based ultrahigh temperature alloy
UR - http://www.scopus.com/inward/record.url?scp=77955414325&partnerID=8YFLogxK
U2 - 10.1016/j.apsusc.2010.05.091
DO - 10.1016/j.apsusc.2010.05.091
M3 - 文章
AN - SCOPUS:77955414325
SN - 0169-4332
VL - 256
SP - 7462
EP - 7471
JO - Applied Surface Science
JF - Applied Surface Science
IS - 24
ER -