The Study on Tempered Treatment and Fracture Behaviors of Low Silicon CA-15 Martensitic Stainless Steel

• Main Authors: Hwei-Yuan Teng, 鄧惠源
• Other Authors: Cheng-Hsun Hsu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/83149740803002175911

博士 === 大同大學 === 材料工程研究所 === 91 === Low-silicon CA-15 cast martensitic stainless steel is the similar grade to AISI 403 stainless steel on corrosion resistance. It possesses excellently moderate temperature strength, corrosion resistance, and erosion wear resistance that used in turbine blade, propeller etc the high quality stressed part. This paper studied the procedure parameters selection of annealing, austenitization and quenching, and tempering on microstructure and mechanical properties. Furthermore, elevated/ subzero temperature mechanical properties, fracture mechanics and solid particle erosion behavior of low silicon CA-15 tempered stainless steel also been discussed. The results show that isothermal annealing on 700℃ hold 6 hours can obtain the best result of softening. The 1010℃/ 2 hours austenitized then air quenched showed the better properties on hardening and microstructure. Tempered at 300-400℃, the martensite matrix decompose to temper martensite and alloy carbides, the chromium rich carbide precipitated around grain boundary at the same period. These cause the secondary hardening effect and temper martensite embrittlement effect (TME). The secondary hardening effect is not appeared on subzero test and weak effect is to substitute it. Tempering on high temperature can substantially improved the impact toughness and lowered the ductile to brittle transition temperature (DBTT). Tempering during 300-400℃, fracture toughness and exponent index of fatigue crack growth (FCG) can be improved. The fracture toughness rose and the exponent of fatigue crack propagation reduced. The fatigue crack propagation micrographic showed the crack paths be retarded, deflected and branched by strengthened martensite matrix and precipitated carbides around grain boundary. The plastic deformation features of fracture toughness specimen are obvious showed on 150℃ test. The affected trend of different heat treatment specimens on fracture toughness are similar to hardness at RT/-150℃ test. At solid particle erosion mechanism, cutting is the mainly mechanism on low incident angle erosion, smear crater is on medium incident angle erosion, indentation crater is on high incident angle erosion and the crack and platelet mechanism are significant fracture mechanism on all angle erosion. The maximum erosion rate is occurred at incident angle was 30° and the maximum erosion penetrant is occurred at incident angle was 45°. The TME effect by 300℃ tempered cause the erosion crack occurred along the martensite grain boundary obvious.