Premium
The effect of carbides on fracture toughness of steels of ferritic matrix
Author(s) -
Pacyna Jerzy,
Witek Lesław
Publication year - 1988
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.198801608
Subject(s) - cementite , carbide , materials science , fracture toughness , metallurgy , grain boundary , ferrite (magnet) , volume fraction , toughness , composite material , microstructure , austenite
The authors evaluated the effect of the volume fraction and the dispersion rate of cementite on fracture toughness of ferrite. The investigations were performed at ‐196°C on five types of carbon steels containing 0.028–1.22% of C in which cementite was coagulated at 700°C for 1–8 h from the quenched state. It was determined that the fracture toughness of steel increases very strongly up to the content of carbides of about 7% by volume. At the same time, hardness and strength of these steels grow. First of all, this is the result of size reduction of ferrite grains by fine carbides. These carbides, distributed almost exclusively on grain boundaries, can only participate in the transmission of the crack to the neighbouring grain. At larger contents of carbides, their dispersion rate decreases while their number in the grain volume grows. Fine carbides from inside of the grains set the path of easy cracking on the boundaries with the ferritic matrix while the coarse carbides crack in front of the fracture. As a result, the steel fracture toughness decreases. The fracture development by means of carbides is less harmful than on the carbide/matrix boundaries.