Microstructure and Properties of High Chromium White Cast Irons Alloyed With Boron

Abstract

The microstructure and mechanical properties of high chromium white cast iron with composition: 2,6÷3,4% C; 0,9÷1,1% Si; 0,8÷1,1% Mn; 1,0÷1,3% Mo; 12,3÷13,4% Cr, additionally doped with boron in an amount of 0,18% to 1,25% is investigated. The microstructure of six compositions of white cast irons is studied by means of an optical metallographic analysis - one without boron, and the others contain 0,18%; 0,23%; 0,59%; 0,96% and 1,25% boron. A test is performed to determine: hardness by the Rockwell method; microhardness; bending strength and impact toughness. It was found that at a boron content of 0,18%; 0,23% and 0,59%, the structure of white cast irons is subeutectic, with impact toughness in the range of 1,80÷1,52 J/cm2; with a boron content of 0,96%, the structure of white cast iron is close to the eutectic, with impact toughness 0,98 J/cm2 ; at a boron content of 1,25% the structure of white cast iron is supereutectic and the impact toughness decreases to 0,68 J/cm2. With a change in the boron content from 0,8% to 1,25%, the amount of carbide phase in the structure of white cast iron increases, which leads to an increase in hardness from 53 to 59 HRC. The highest bending strength (Rmi=660,85 MPa) was obtained in white cast irons with a boron content of 0,23%.

Effect of Boron on the Wear Behavior of High Chromium White Cast Irons

“…The cast irons studied contain about 1% molybdenum, dew to carbides type M6C и M2C are possible in the structure. Microstructure of the cast irons without boron and with 0,18; 0,23 and 0,59% В is subeutectic, with 0,96 % В -with 0.96% B -close to the eutectic and with 1.25% B -supraeutectic [1]. Fig.…”

“…In the structure of high chromium white cast irons with chromium about 13% the main carbide is M7C3 [1][2][3]. Carbides type M3C и M23C6 also persist in the structure of these cast irons.…”

“…These carbide phases differ in a chemical composition and morphological characteristics. The operational properties of these cast irons are determined from a predominant carbide type in their structure to a significant extent [1][2][3]. For this reason, the research directed towards at controlling and improving the operational properties of high-chromium white cast irons includes studying the changes in the carbide phases as a function of the alloying elements present in the structure, including the element boron [1][2][3][4][5][6].…”