Designing a Graphitic White Iron: Microstructures and Properties

Document Type

Conference Proceeding

Publication Date

2019

Publication Title

2019 AISTech Conference Proceedings

DOI

10.33313/377/107

Abstract

The word “tribology” was first reported by Jost [1] in a landmark report. Its popular English language equivalent is “wear”, which is defined as “alteration of a solid surface by progressive loss or progressive displacement of material due to relative motion between that surface and a contacting substance or substances” by ASTM G40 [2]. As a major problem in modern machinery parts, wear is very crucial in metal-to-metal wear systems, such as rolling bearing, gears, and seals. The wear of parts, the cost of repair and replacement of these parts, and the associated downtime related to these activities results in significant costs to the industry [3]. A wide variety of hard facing materials have been invented to slow down the wear rate and reduce the associated cost. The most popular ones, today, are silicon carbide, tungsten carbide, Ni-Resist cast iron, Stellite and aluminum oxide [4], but most of these hard facing materials are too expensive, due to either the cost of alloy addition or manufacturing processing. Alternative option for such application is high Cr white iron. Containing M7C3 carbide of high hardness (1100-1600 HV) [5] makes it relatively wear resistant, while its alloy cost is much lower compared with foresaid hard facing materials. The M7C3 carbides in high Cr white iron are the primary phases of hexagonal shape and can work as the “stoppers” to decrease the wear rate during the wear application [6]. However, with about 10-30 wt.% chromium addition, high Cr white iron has a poor thermal diffusivity. Frictional heating generated during the wear application can over heat the wear surfaces and induce severe adhesive wear to the wear components [7-9]. It was also reported that the wear rate increases substantially at elevated temperatures [9,10].

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