Metal Additive Manufacturing Conference - MAMC 2022

Laser deposition processes such as laser metal deposition or direct energy deposition are additive manufacturing techniques that offer a great flexibility and efficiency compared to traditional subtractive manufacturing processes. However, the extreme thermal conditions during deposition and the rapid cooling times pose great challenges in the alloy design. This work illustrates how to overcome these challenges in order to design nickel, iron and titanium-base self-lubricating alloys. The selected alloys are blended with lubricious compounds for achieving a microstructure containing soft metals inclusions or metal sulfides. The goal is the development of metallic alloys able to provide low friction in metal-to-metal contacts operating in extreme environments such as high temperature or vacuum, without the aid of external lubricants.

The microstructure and phase composition of the deposited self-lubricating alloys are characterized using X-ray diffraction, scanning and transmission electron microscopy, showing the importance of having the soft metal as single phase without forming intermetallic compounds or being in solid solution. Additionally, the role of the metal sulfide composition and stoichiometry formed during the laser deposition process on friction is discussed. Afterwards, the friction and wear performance of the developed alloys are evaluated using high temperature tribological tests in air and vacuum. The results show that the self-lubricating laser deposited alloys are able to control friction from room temperature to 600 °C in ambient air and at least until 300 °C in vacuum. This overall tribological performance makes the presented self-lubricating alloys potential candidates for high temperature forming and aerospace applications.