Abstract
The initial as-cast microstructure of high-chromium white cast iron (2.08% C, 12.1% Cr), including austenitic dendrites in a matrix of a eutectic mixture of austenite and M7C3 carbides. Heat treatment of as-cast iron leads to a transformation of the matrix from austenite to martensite phase. The secondary M23C6 carbide precipitated from matrix improving the hardness of sample from 48 HRC to 62 HRC. JMatPro simulations of volume fraction phase for Fe-C-Cr-Mn alloy shows M7C3 and austenite phases are stable at austenitization temperature (1000 °C). Eutectic carbide of M7C3 is a stable phase in the alloy which is undissolved in the matrix during the heat treatment process. The HR-TEM images of heat-treated sample revealed that both eutectic M7C3 carbide and ultrafine secondary M23C6 carbide particles distributed on the martensite matrix.
Highlights
High Cr white cast iron (HCCI) alloys containing chromium between 12 and 30% have a good abrasion resistance which is widely used in wear applications, such as mineral processing, cement production and steel manufacturing industries [1,2,3,4,5,6]
In heat treatment (HT) process, while the austenite phase transferred to martensite resulting in the change of composition in the matrix, M23C6 carbide particles precipitated
In HT process, while the austenite phase transferred to martensite resulting in the change of composition in the matrix, M23 C6 carbide particles precipitated
Summary
High Cr white cast iron (HCCI) alloys containing chromium between 12 and 30% have a good abrasion resistance which is widely used in wear applications, such as mineral processing, cement production and steel manufacturing industries [1,2,3,4,5,6]. The abrasion resistance of HCCI alloys is about 20–25 times better than low carbon steels, due to the distribution of carbide phases on the matrix [2,7]. A coarse carbide phase network formed directly from liquid solution leads to poor fracture properties and relatively high wear rate [8,9] This network is very stable and unaffected by the heat treatment (HT) process. In the destabilization HT process, secondary carbide phases are precipitated at low austenitization temperature, causing a reduction in carbon and chromium content results in a diffusionless transformation phase from austenite to martensite. A sub-critical HT is useful to reduce the retained austenite and reinforce martensite matrix by precipitation of considerable secondary carbides [12].
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