고온변형과 열간노출에 따른 주조용 합금 738LC의 탄화물 분해거동 고찰

주동원; 조창용; 김두현; 서성문; 이영찬; 김두수; 최승주; Dong-Won Joo; Chang-Yong Jo; Doo-Hyun Kim; Seong-Moon Seo; Young-Chan Lee; Doo-Soo Kim; Seung Joo Choe

Korean Journal of Materials Research, Vol.10, No.2, 111-116, February, 2000

Export Citation

고온변형과 열간노출에 따른 주조용 합금 738LC의 탄화물 분해거동 고찰

Effects of High Temperature Deformation and Thermal Exposure on Carbide Reaction Cast Alloy 738LC

주동원, 조창용 , 김두현 , 서성문, 이영찬¹, 김두수¹, 최승주

한국기계연구원 재료공정연구부 내열재료그룹
¹한국전력공사 전력연구원 발전연구실

Dong-Won Joo, Chang-Yong Jo , Doo-Hyun Kim , Seong-Moon Seo, Young-Chan Lee¹, Doo-Soo Kim¹, and Seung Joo Choe

Materials Processing Department, Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon, 641-010, Korea
¹Power Generation Laboratory, Korea Electric Power Research Institute, 103-16, Munji-dong, Yusung-ku, Daejon, 305-380, Korea

초록

니켈기 주조용 합금 738LC를 816°C 와 982°C 에서 크리프 파단 시험과 열간 노출시험을 통해 온도와 응력 변화에 따른 파단양상, 탄화물과 σ 상의 석출 거동에 대해 조사하였다. 816°C /440MPa에서는 크리프 파단양상이 전단변형에 의한 입내파괴를 나타내었으나, 982°C /152MPa에서는 표면과 접하는 결정입계에서 입계산화에 의해 표면에너지의 감소로 균열이 나타나 진행되는 입계파괴가 나타났다. M(sub)23C(sub)6 탄화물이 816°C 에서는 주로 결정입계에서와 전단변형에 의한 입내균열을 따라 석출하였으나, 982°C 에서는 결정입계 뿐만 아니라 입내에서는 석출하였으며 석출양은 증가하였다. σ 상은 Cr(sub)23C(sub)6 탄화물에서 핵생성 후 기지로 성장하며, 온도가 높고 응력이 주어지면 Cr(sub)23C(sub)6 탄화물의 양이 증가하여 σ 상의 석출도 많아졌다.

Fracture mode and carbide reactions of cast alloy 738LC during thermal exposure and creep at 816°C /440MPa and 982°C /152MPa were investigated. Crystallographic transgranular failure was observed in the specimen crept at 816°C due to shearing on the slip plane. Because selective oxidation at the grainboundaries which was exposed at the surface leads reduction in surface energy, however, early initiation of crack at the grainboundaries and intergranular failure were observed in the specimen crept at 982°C /152MPa. As a result of decomposition of MC carbide at the tested temperatures, M(sub)23C(sub)6 carbide precipitated either on the grainboundaries or on the deformation band. The applied stress enhanced decomposition of MC. σ phase nucleated from Cr(sub)23C(sub)6 then grew to the γ + γ ` matrix. Precipitation of σ was accelerated by increasing temperature and applied stress.

Keywords:Thermal exposure;Creep test;Crystallographic failure;Intergranular failure;Precipitates(γ ` . MC . M 2 3C 6 . σ )

[References]

Yoshioka Y, Saito D, Fujiyama K, Okabe N, Proceeding of ASM 1993 Materials Congress Materials Week '93, 53 (1993)
Jianting G, Ranucci D, Picco E, Strocchi PM, Metall. Trans. A, 14A, 2329 (1983)
Henderson PJ, Scripta Metallurgica, 22, 1103 (1988)
Castillo R, Koul AK, Immarigeon JPA, Reichman S, et al., Metallurgical Scoiety, 805 (1988)
Mihalisin JR, Trans., 239, 180 (1967)
Sims CT, Hagel WC, Superalloys Ⅱ, 111 (1986)
Jeffies E, Trans., 60, 474 (1919)
Oh DK, Joo DW, Jo CY, Seo SM, Kim DH, Choe SJ, Lee SL, J. Korean Inst. Met. Mater, 37(8), 937 (1999)
Wagner C, Ber. Bunsenges Phy. Chem., 63, 772 (1959)
Schubert F, Donachie MJ, Superalloy Source Book, 71 (1984)
Wlodek ST, Trans., 230, 1078 (1964)
Peckner D, Bernstein IM, Handbook of Stainless Steels/ McGraw-Hill Book Co., pp.4-47, 1987 (1987)
Sundararaman M, Mukhopadhyay P, Banerjee S, Loria EA, Minerals. Metals. Materials Society, 419 (1994)
Piearcey BJ, Smashey RW, Trans., 239, 451 (1967)
Decker RF, Sims CT, Sims CT(ed.), Hagel WC(ed.), The Superalloys (1972)

[Related Articles]

[1] Yoshioka Y, Saito D, Fujiyama K, Okabe N, Proceeding of ASM 1993 Materials Congress Materials Week '93, 53 (1993)

[2] Jianting G, Ranucci D, Picco E, Strocchi PM, Metall. Trans. A, 14A, 2329 (1983)

[3] Henderson PJ, Scripta Metallurgica, 22, 1103 (1988)

[4] Castillo R, Koul AK, Immarigeon JPA, Reichman S, et al., Metallurgical Scoiety, 805 (1988)

[5] Mihalisin JR, Trans., 239, 180 (1967)

[6] Sims CT, Hagel WC, Superalloys Ⅱ, 111 (1986)

[7] Jeffies E, Trans., 60, 474 (1919)

[8] Oh DK, Joo DW, Jo CY, Seo SM, Kim DH, Choe SJ, Lee SL, J. Korean Inst. Met. Mater, 37(8), 937 (1999)

[9] Wagner C, Ber. Bunsenges Phy. Chem., 63, 772 (1959)

[10] Schubert F, Donachie MJ, Superalloy Source Book, 71 (1984)

[11] Wlodek ST, Trans., 230, 1078 (1964)

[12] Peckner D, Bernstein IM, Handbook of Stainless Steels/ McGraw-Hill Book Co., pp.4-47, 1987 (1987)

[13] Sundararaman M, Mukhopadhyay P, Banerjee S, Loria EA, Minerals. Metals. Materials Society, 419 (1994)

[14] Piearcey BJ, Smashey RW, Trans., 239, 451 (1967)

[15] Decker RF, Sims CT, Sims CT(ed.), Hagel WC(ed.), The Superalloys (1972)