| Title |
Deformation behavior of Flame-hardened Surface Layer of 12Cr Steel by Supersonic Water Drop Impacts |
| Authors |
김광호(Gwang Ho Kim); 이민구(Min Ku Lee); 김경호(Kyeong Ho Kim); 김흥회(Whung Whoe Kim); 김길무(Gil Mu Kim) |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
12Cr steel; Flame hardening; Water drop impact; Erosion; Surface heat treatment |
| Abstract |
Water drop impact erosion properties of the 12Cr steel, currently used as nuclear steam turbine blade material, surface-hardened by the flame hardening process have been characterized. For this, variations of both the maximum erosion depth de,,,,ax and volume loss V with the cumulative impacts n at the supersonic impact velocity (~350 m/s) have been investigated for the as-received and flame-hardened 12Cr steels with different hardnesses. Typically all the samples showed an erosion-time characteristic involving the incubation period initially followed by the steady state period. It is also found that the d_(e,max) increases stepwise-like with the number of impacts n, which results from a sudden formation of craters by crack propagation. Compared to those for the as-received 12Cr steel, the flame-hardened ones showed an excellent resistance to water drop impact erosion with 2.2~2.8 times higher incubation time n, and 115~1/8 times lower erosion rate a. In the incubation period the as-received 12Cr steel was damaged by ductile depression and ploughing, while the flame-hardened 12Cr steel by fatigue cracks and brittle platelet deformation. Erosion in the steady state period was developed by the cleavage fracture commonly. (Received July 22, 2004) |