Abstract
Hardfacing alloys with varying amounts of graphite content were prepared on a surface of 45 steel using flux-cored wire open-arc overlaying. Testing was conducted using SEM, TEM, XRD, a Rockwell hardness apparatus and an abrasion tester to study the effect of variation of graphite content on the microstructure, hardness and abrasive resistance of the hardfacing alloy. The results show that the microstructure of the hardfacing layer consisted of martensite, austenite and NbC. As graphite content increased, martensite content increased, austenite content decreased, and the size of in situ-generated NbC particles increased. Additionally, the abrasive resistance of the hardfacing alloy, which could exceed 4 times that of the 45 steel base material, was related to the microstructure and the size of NbC particles, and generally shared the same variation trend as the hardness changes in the hardfacing layer. DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16678
Highlights
In welding and metallurgical processes, Nb [1 – 4], Ti [5 – 9], B [10], W [11 – 12] and other alloying elements are prone to form a hard-strengthening phases, leaving the hardfacing alloys with relatively high hardness and good abrasive resistance
The hardfacing alloys consisted of ferrite, martensite, austenite, NbC and MC (M representing Fe and/or Cr) phases
In the sample #1 without graphite addition, only ferrite and/or martensite, NbC and MC phases were found The austenite diffraction peaks appeared from sample #2 and were gradually heightened with the graphite additions increasing
Summary
In welding and metallurgical processes, Nb [1 – 4], Ti [5 – 9], B [10], W [11 – 12] and other alloying elements are prone to form a hard-strengthening phases, leaving the hardfacing alloys with relatively high hardness and good abrasive resistance. Its hardness and melting point are both very high, NbC is not often used due to the small size of its hard-phase particles, which tend to be lost during cutting, reducing the wear-resisting function of the layer [16] For this reason, most of the existing literature and data suggest that the in-situ synthesized hard phases may combine better with a base interface than with external hard-phase particles, as this can reduce the peeling and wearing rate of the abrasion resistant alloy [17]. The abrasive resistance of hardfacing alloys depends on several factors, such as the type, shape and distribution of the hard phases as well as the tenacity and strain-hardening behavior of the base material [19]
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