Kinetic Parameters of Secondary Carbide Precipitation in High-Cr White Iron Alloyed by Mn-Ni-Mo-V Complex

Pulsed plasma deposition of Fe-C-Cr-W coating on high-Cr-cast iron: Effect of layered morphology and heat treatment on the microstructure and hardness

“…Isothermal HTs of as-cast HCCIs at 900-1000 o C usually aim at the precipitation of fine secondary carbides of M7C3 and M23C6 stoichiometries [20,22,23,43]. These have most likely nucleated as nanosized particles [44] mostly on defects inside austenite grains due to Cr atoms volume diffusion [23]. In contrast, in Cr28-deposited layers, precipitation has led to the formation of relatively coarse carbide particles in the form of a carbide network, as illustrated in Fig.…”

“…[19][20][21]. As a rule, these alloys are subjected to bulk heat treatment (HT) in order to increase their hardness and wear performance [22,23]. However, the HT HCCIs do not always meet the growing demands for operational durability.…”

The Effect of Cooling Conditions on Martensite Transformation Temperature and Hardness of 15% Cr Chromium Cast Iron

“…Precipitation of carbides in high-chromium cast iron leads to impoverishment of austenite in carbon, chromium, and other elements included in composition of chromium carbides. Authors of the paper [35] demonstrated that precipitations of chromium carbides from austenite in a cast iron containing 14.55% Cr proceeded fastest at the temperature of 950 • C. The process started as early as after 10 s and ended within the period of 160 min. The austenite impoverished in carbon and other alloying elements, transforms into martensite in the course of rapid cooling.…”

“…Studies on development of new heat treatment schedules for high-chromium cast iron were conducted by authors of papers [32][33][34][35]. From this point of view, significant are studies on working out TTT (Time -Temperature -Transformation) plots serving as a base for selection of heat treatment parameter values [35].…”

“…Duration the first heat treatment variant was 31 h and was longer compared to the duration of the second variant which lasted for 17 h. Subcritical soaking temperatures were 650 • C and 750 • C in the first variant of the treatment and 725 • C in the second variant. For a high-chromium cast iron with the same chemical composition (14.55% Cr), the study [35] presented a heating dilatogram from which it followed that the eutectoid transformation start temperature was TAc 1 p = 760 • C. Assuming that the rate of heating for which the dilatogram was taken corresponded to the heating rate applied in both of the softening treatment variants, an opportunity appeared for further decrease of hardness at shorter treatment cycle. That can be achieved by increasing the annealing temperature up to the range 725-760 • C. Authors of [33] reported that in the case of high-chromium cast iron containing 2.7% C, 14.55% Cr, 2.20% Mn, and 0.93% Ni, austenitizing at temperature 950 • C for the period of 2 h secured precipitation of secondary carbides, mainly M 7 C 3 , and the following cooling in oil enabled partial transformation of supercooled austenite into martensite.…”