Wear Protection by Fe‐B‐C Hard Phases

Abstract

Four as-cast iron alloys with (mass%) 1B þ 3C, 2B þ 2C, 3B þ 1C and 4B þ 1C were investigated in respect to their microstructure by optical and scanning electron microscopy with EDX and ESBD and by microprobe analysis. The microhardness of eutectic Fe 3 (C,B) increased with the B/C ratio and raised the resistance to scratching by Flint particles. The low melting range of the castings was used for the powder metallurgical production of a metal matrix composite by liquid phase sintering of admixed hard particles in an Fe-B-C base material. Abrasive wear tests showed that the eutectic carborides in the base material raised the wear resistance even more than the admixed particles.

Solidification and phase formation of alloys in the hypoeutectic region of the Fe–C–B system

“…Surface energy r in J/cm 2 Interface mobility l in cm 4 /(Js) Liquid c-Fe 0.2B to 1132°C in alloy 1.8B. At the same time, the liquidus temperature decreases with the B content from 1476°C in alloy 0.2B to 1332°C in alloy 1.8B.…”

“…Due to their stabilizing effect on the Fe 2 B phase, the elements Mn and Cr are also of high importance in the development of new Fe-C-B steels. With respect to the literature, it is known that Mn and Cr are enhancing the hardness and the fracture toughness of M 2 B phase (Fe 2 B $ 1500-1700 HV, 3.8 MPa m 1/2 -Cr 2 B $ 2000 HV, 7.8 MPa m 1/2 ) [2,4,34,35]. As an example, the influence of Cr on the stabilization of the Fe 2 B phase is illustrated in Fig.…”

“…In wear protection applications, boron is used in larger amounts (>2.5 mass%) to form coarse hard phases of the type M 23 (C,B) 6 , M 3 (C,B), M 2 B, and M 3 B 2 . Borides and carboborides with increasing B content are preferable with respect to hardness and elastic modulus as compared to carbides and thus decrease the abrasive wear rate [2,8]. Applications can be found in white cast iron [9,10], deposition welding [2,11,12], thermally sprayed coatings [13,14], and surface boriding [15].…”

“…The hardness of the resulting hard phases formed with B have the same order of magnitude or exceed that of the chromium carbide Cr 7 C 3 (1500-1600 HV), which is a commonly used hard phase in tool steels (i.e. boron cementite Fe 3 (C,B) with a hardness of 1300-1500 HV and Fe 2 B with a hardness of 1600-1700 HV) [1][2][3][4]. In this case, carbon (C) no longer contributes to the formation of hard phases and is therefore primarily used to improve the hardenability of the iron matrix.…”

Effect of heat treatment on the microstructure, hardness and abrasive wear resistance of high chromium hardfacing

“…Previous work (Chotěborský et al 2011) showed that increasing the volume fraction of eutectic carbides improves the abrasion resistance. Other possibility for increasing the abrasion resistance is the use of carbide forming element such as vanadium, tungsten, molybdenum or niobium into hardfacing metals (Berns 2003;Berns et al 2011). Especially niobium is an alloy which is currently used for creating microstructure of hardfacing with very hard niobium carbide (NbC) (Xiaohui et al 2008).…”