The Role of Manganese on Microstructure of High Chromium White Cast Iron (original) (raw)
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Microstructure and properties of high chromium white cast iron in different treatment states
1998
Different combinations of critical and subcritical heat treatments variously modify the initial as cast microstructure of high chromium white cast irons leading to secondary carbide precipitation of different extent and nature. Destabilisation (critical heat treatment) of austenite at 970uC for 2?5 h followed by annealing (subcritical heat treatment) at 600uC for 13 h results in massive precipitation of M 23 C 6 carbide particles along with spheroidised M 7 C 3. The reversed order of heat treatments leads to extensive precipitation of M 7 C 3 secondary carbide particles. Mo has a favouring effect on the hardness of the microstructures containing pearlite by limiting pearlite formation. The gradual increase in the alloying additions, C and Cr, increases the hardness of the materials at the different treatment states by inducing carbide precipitation. The increase in the Si content leads to the opposite effect by favouring pearlite formation.
Microstructural Modifications of AsCast High-Chromium White Iron by Heat Treatment
Journal of Materials Engineering and Performance, 2009
The initial as-cast microstructure of a high-chromium (2.35% C, 18.23% Cr) white cast iron consisting of primary austenitic dendrites and a eutectic mixture of M7C3 carbides/austenite was extensively modified by four different heat treatments: H.T.A: destabilization (970 °C-2.5 h), H.T.B: destabilization/subcritical treatments (970 °C-2.5 h + 600 °C-13 h), H.T.C: subcritical treatment (600 °C-13 h) and H.T.D: subcritical/destabilization treatments (600 °C-13 h + 970 °C-2.5 h). H.T.A leads to martensitic structures that present considerable precipitation of cubic secondary carbide particles of M23C6 type. H.T.B produces pearlitic structures and causes further carbide precipitation and pre-existent carbide particle shape modifications. H.T.C extensively modifies the initial as-cast structure to more pearlitic morphologies accompanied with spheroidization/degradation of the M7C3 primary carbide structure. H.T.D causes extensive formation of secondary carbide particles within the primary austenitic matrix; the latter has been mainly transformed to martensite. The effect of each heat treatment on the hardness of the alloy was correlated with the attained microstructure.
Investigation on Microstructure of Heat Treated High Manganese Austenitic Cast Iron
MATEC Web of Conferences, 2016
The effect of manganese addition and annealing heat treatment on microstructure of austenitic cast irons with high manganese content (Mn-Ni-resist) were investigated. The complex relationship between the development of the solidification microstructures and buildup of microsegregation in Mn-Ni-resist was obtained by using microstructure analysis and EDS analysis. The annealing heat treatment was applied at 700°C up to 1000°C to investigate the effect of the annealing temperature on the microstructure. This experiment describes the characterization of microsegregation in Mn-Ni-reist was made by means of point counting microanalysis along the microstructure. With this method, the differences of silicon, manganese and nickel distribution in alloys solidified in the microstructure were clearly evidenced. The results show microstructure consists of flake graphite embedded in austenitic matrix and carbides. There is segregation of elements in the Late To Freeze (LTF) region after solidification from melting. Manganese positively with high concentration detected in the LTF region. As for heat treatment, higher annealing temperature on the Mn-Ni-resist was reduced carbide formation. The higher annealing temperature shows carbide transformed into a smaller size and disperses through the austenitic matrix structure. The size of carbide decreased with increasing annealing temperature as observed in the microstructure.
International Journal of Cast Metals Research, 2009
Different combinations of critical and subcritical heat treatments variously modify the initial as cast microstructure of high chromium white cast irons leading to secondary carbide precipitation of different extent and nature. Destabilisation (critical heat treatment) of austenite at 970uC for 2?5 h followed by annealing (subcritical heat treatment) at 600uC for 13 h results in massive precipitation of M 23 C 6 carbide particles along with spheroidised M 7 C 3 . The reversed order of heat treatments leads to extensive precipitation of M 7 C 3 secondary carbide particles. Mo has a favouring effect on the hardness of the microstructures containing pearlite by limiting pearlite formation. The gradual increase in the alloying additions, C and Cr, increases the hardness of the materials at the different treatment states by inducing carbide precipitation. The increase in the Si content leads to the opposite effect by favouring pearlite formation.
Metals, 2020
Hypoeutectic white cast irons containing 25% Cr are used in ore-processing industries due to their high resistance to erosive wear. Applying a Design of Experiments (DoE), the aim of this study is to analyse the influence of thermal processing factors on the microstructural variation of a white cast iron containing 25% Cr and 0.6% Mo. The carbides present in the as-cast state are of the M7C3, M2C, and M3C types. M2C carbides precipitate on the eutectic M7C3 carbides favoured by heterogeneous nucleation conditions. Two kinetics compete during the destabilisation of austenite. One dissolves those eutectic carbides precipitated as a result of non-equilibrium solidification (M7C3 and M2C), while the other enables the precipitation of secondary M7C3 and M23C6 carbides. The M7C3 carbides begin to precipitate first. Low destabilisation temperatures and short dwell times are insufficient to dissolve the precipitated eutectic carbides from non-equilibrium conditions, thus favouring the prese...
Effect on Mechanical Properties of Heat Treated High Manganese Austenitic Cast Iron
MATEC Web of Conferences, 2016
This work presents an attempt to study the effect of manganese addition and heat treatment on higher carbon austenitic cast iron to form high manganese austenitic cast iron with reduced nickel content (Mn-Ni-resist) on mechanical properties. The combination on microstructure (microsegregation), mechanical properties and the relationship of heat treatment on the alloy were analyzed. For this purpose Mn-Ni-resist (4.50C, 2.64Si, 6.0 Mn, 10 Ni) was melted and cast in the form of Y-block test pieces. Four different heat treatment procedures were applied to the as-cast to investigate the effect of alloy modifications on Mn-Ni-resist. Optical and scanning electron microscopies were used for microstructure investigation. To determine the mechanical properties tensile test and hardness test were carried out. The result indicates both composition and heat treatment affect the performance of Mn-Ni-resist intensively. Microprobe analysis shows some silicon segregation near the graphite and practically little segregation of manganese. The increase in manganese contents developed some fractions of segregated carbide structures in LTF region located at austenite eutectic cell frame, which caused the tensile properties to drop in a small range. Application of annealing heat treatment gradually changed the carbide formation, so is the material's strength.
Effect of titanium on the as-cast microstructure of a 16%chromium white iron
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005
This research work studies the effect of systematic titanium additions (up to 2 wt.%) to a 16%Cr, 2.5%C white cast iron. The study was undertaken in six laboratory made alloys with different titanium amounts. Alloys were melted in an open induction furnace by using high purity raw materials. Such additions caused small hard titanium carbide particles to precipitate within the proeutectic austenite therefore promoting a strengthening of matrix; such particles also contributed to increase bulk hardness of the overall alloy. A structure refinement, as measured by the secondary dendrite arm spacing, was also observed as the titanium amount was increased. Titanium carbide precipitation caused a small decrease in the eutectic carbide volume fraction. The fracture toughness remained constant since the strengthening of matrix was compensated with a decrease in the volume of eutectic carbides. According to this study, titanium can be used as an alloying element to increase the hardness and perhaps wear resistance without affecting fracture toughness in high-chromium cast alloys. The results are discussed in terms of the precipitation nature of such small hard titanium particles.
Journal of Materials Science, 2004
Three high chromium white cast irons were examined in the as-cast state to determine the effect of the carbon content on the fracture toughness. The plane strain fracture toughness K Ic and the fracture strength were measured for each alloy. X-ray mapping was used to identify the phases on the fracture surfaces. Scanning electron fractography and optical microscopy were used to determine the volume fraction of each phase on the fracture surfaces. It was found that most fracture occurred in the eutectic carbides, but that for the alloys with a reduced volume fraction of eutectic carbides, a small amount of crack propagation occurred in the austenitic dendrites. This change in crack path correlated with an increase in fracture toughness. The Ritchie-Knott-Rice model of brittle fracture was applied. It was found to sensibly predict the critical length for fracture for each alloy. Deep etching was employed to examine the distribution of eutectic carbides. It was found that the eutectic carbides formed a continuous network in each case.
In this study, high chromium white iron (HC-Wi) alloy and the Hadfield steel were studied. The microstructure of this high-chromium iron was studied using Metallurgical optical microscopy (OM) and compared to the Hadfield steel. The hardness and unnotched charpy impact strength of the HC-Wi alloy and Hadfield steel were examined at ambient temperature in the as-cast and heat-treated conditions. A pin-on-disc test at linear speed of 1.18 m/s and a 10 N normal load was employed to evaluate the wear behavior of both steel samples. Microstructural results showed that varying the carbon level in HC-Wi alloys can affect the chromium carbide morphology and its distribution in the austenite matrix which leads to considerable changes of the mechanical properties. Abrasion test showed that HC-Wi alloys have superior wear resistance, about three times of the Hadfield steel.
2017
High Cr white cast irons are an important class of wear resistant materials currently used in a variety of applications that requires high wear resistance and reasonable toughness. The outstanding performance of these alloys is due to the presence of large amounts of chromium carbides which exhibit high hardness. The size, type and morphology of these carbides control the wear resistance and toughness. The microstructural characteristics of these alloys, and consequently their wear resistance, can be extensively changed by varying the chemical composition or the solidification rate or by specific heat treatment after casting. Heat treatments for all high-Cr WCI alloys are essential to change their microstructure and therefore, to improve their wear resistance to suit the individual application requirements. Changing in chemical composition and heat treatment carried out to this alloy related to microstructural characteristics and mechanical properties of high Cr white cast iron allo...