*2.2.1 "Amorphous" material hardbandings*

In 1990, Liquidmetal Technologies LTD developed a chromium alloy hardbanding material, named Armacor MTM. This material is an "amorphous" chromium alloy, the microstructure of which has no grain boundary and is distributed in a single atomic structure. The outstanding feature of this metal structure is that it has a very low friction factor. Therefore, the wear of the casing is very small, which can greatly reduce the wear of the casing. It is the first kind of "casing-friendly" hardbanding material, which represents a significant improvement in hardbanding technology. But because the "amorphous" hardbanding has only a very thin layer with poor abrasion performance under the high pressure, the main shortcoming of this hardbanding material is insufficient wear-resistant ability, which makes the drill pipe joint not well protected [14].

Subsequently, the Liquidmetal Technologies company has developed some new hardbanding materials, such as Armacor MStar and Armacor TMax. Till now, Armacor MStar material is their most casing-friendly material [15]. Armacor TMax material is their hardest, most wear-resistant material, which is ideal for open-hole drilling environments. In addition to this, as amorphous materials, these materials can lead to improved corrosion resistance and resistance to reactivity at elevated temperatures (oxidation, vulcanization), which are suitable for geothermal well drilling and deep well drilling.
