Investigation on the microstructural evolution and precipitation hardening mechanism of 1Cr15Ni36W3Ti superalloy with varied C contents

• Main Authors: Haoze Li, Bochuan Jiang, Ming Gao, Weiwei Xing, Yingche Ma, Kui Liu
• Format: Article
• Language: English
• Published: Elsevier 2019-11-01
• Series: Materials & Design
• Online Access: http://www.sciencedirect.com/science/article/pii/S0264127519304216

Impacts of C content on the microstructural evolution and precipitation hardening mechanism in 1Cr15Ni36W3Ti was studied by phase modelling, microstructural analysis and room-temperature tensile test. The casting material was composed of γ, interdendritic primary MC and secondary MC carbides. The morphology of the primary MC carbide, the amount of which was proportional to the C content, transformed from bulk and short rod-like to skeleton with the C content increasing. The primary MC carbides crushed in pieces during hot working and served as grain-boundary pinning particles during solution treatment. The increased C content made the precipitation of the γ′ phase transform from nucleation dominated to growth dominated at the second-stage aging treatment, which increased the average diameter but lowered the volume fraction of the γ′ phase. Accordingly, the γ′/dislocation interaction transformed from dislocation shearing to complete Orowan looping upon yielding, leading to the declined yield and tensile strength. The coherency strengthening mechanism played an important role in the reinforcement of this alloy. The C content of this kind of superalloy with a low amount of γ′ forming element should be limited below a proper level so as to maximize the coherency strengthening contribution. Keywords: Fe-Ni based superalloy, C content, γ′ phase, Strengthening mechanism, Tensile property