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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Tribological Evaluation of Candidate Coatings

This SPP project with Novus was to investigate tribological properties of candidate ceramic composites. Systematic tribological bench tests and surface characterization were performed to determine composition-property relationships of several Zr-Ti-B based ceramic composites of different compositions. The lowest friction coefficient was measured with Ti0.6Zr0.4B2 composition tested in the hydraulic oil. Surface characterization suggests a formation of ZDDP tribofilm in the worn region when tested with a hydraulic oil. In all experiments, the ceramic composites did not have measurable wear, but caused material loss of the steel countersurface.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Mechanical and Tribological Performance of Additively Manufactured Nanocrystalline Aluminum via Cryomilling and Cold Spray

In this study, nanocrystalline (NC) aluminum (Al) and magnesium (Mg)-doped Al bulk components were fabricated using a hybrid manufacturing process that combines cryomilling and high-pressure cold spray (HPCS) additive deposition techniques. Yttria-stabilized zirconia (YSZ) was also added during the HPCS process to improve deposition efficiency and build-up thickness via peening. The evolution of morphology, crystallite size, and elemental composition of both cryomilled powders and cold-sprayed (CS’ed) components was systematically characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Mechanical characterization was performed using Vickers microhardness and uniaxial tensile testing, while the tribological behavior was assessed using sliding wear tests under dry/lubricated conditions. XRD analysis revealed that increased cryomilling duration led to significant crystallite refinement, which directly correlated with enhanced hardness and strength. This mechanical strengthening was accompanied by an increase in coefficient of friction (COF) and lower wear rates. The results also showed that the Mg-doped Al exhibited superior hardness, tensile strength, and tribological performance compared to pure Al. The study further explores the underlying mechanisms responsible for these enhancements, highlighting the potential of solute-assisted grain boundary stabilization in tailoring high-performance NC Al alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Tribological behaviors of nanotwinned Al alloys

Wear-induced damages cause significant materials loss each year. Al alloys are widely used by industry but usually have low wear resistance. Here, we compare the tribological behaviors of ultrafine grained Al, a nanoprecipitate hardened Al 7075 alloy and nanotwinned Al–Ni alloys using the nanoscratch. The nanotwinned Al–Ni alloys exhibit lower coefficient of friction and much greater wear resistance than the Al and Al 7075 alloys. Additionally, the enhanced wear properties of Al–Ni alloys arise from their high strength and the evolution of nanotwinned microstructures into gradient nanograins during wear. These findings on fundamental wear mechanisms in nanotwinned alloys may advance the discovery of wear-resistant metallic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Cryo-quenched Fe–Ni–Cr alloy decorative steel single crystals II: Alloy phases, structure, hardness, tensile, tribological, magnetic and electronic properties

We have previously reported (Boatner et al., J. Alloys Compd. 691 (2017) 666–671) on the discovery, formation, processing, and application of a new decorative ternary steel alloy and on its use in a wide range of practical applications including: custom and commercial knives, art objects, jewelry, electronics, and furniture. This decorative property results when polished single crystals of the 70 wt%Fe-15 wt%Ni-15 wt% Cr austenitic alloy are cryo-quenched into the martensitic phase resulting in the formation of a three-dimensional raised pattern of mixed austenitic/martensitic laths. These laths propagate across large dimensions of the material due to the absence of grain boundaries in the single crystal. The macroscopic optically reflective 3-D decorative pattern reproduces the structural symmetry inherent in the single-crystal orientation. This pattern results solely from the metallurgical phase properties of the ternary alloy and is completely distinct from the properties of Damascus steels or more modern so-called pattern-welded steels. Here we use X-ray diffraction, nanoindentation, hardness measurements/scratch testing, tribological measurements, and alloy resistivity and magnetization methods to obtain a more fundamental and comprehensive study of the effects of the austenitic/martensitic phase transition on the structural and physical properties of the 70 wt%Fe-15 wt%Ni-15 wt% Cr alloy. These results reveal new insight into irreversible phenomena that are associated with the inhibited phase transition on heating of the two-phase, mixed austenitic/martensitic structure that is formed subsequent to cryo-quenching the alloy crystal to 77 K.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Graphene oxide gluing layer enabling macroscale tribology applications of pristine graphene

In recent studies of two-dimensional (2D) nanomaterial-based solid lubricants, the importance of durability has been emerging for real engineering-scale applications. To achieve this, a transfer layer formation is essential to prevent the wear of the mechanical systems. However, it has been challenging for pristine graphene (PG) to induce a material transfer due to chemical inertness. In this study, we suggest an easy-to-process strategy to promote the huge material transfer of the PG onto the counterpart contacting material. We utilized graphene oxide (GO) as a gluing layer between the PG film and the counterpart contact surface to realize the superior tribological performance. The high interaction energy of the GO from its functional groups makes a contribution to the material transfer of PG, which is unveiled by a systematic analysis of the counterpart contact surface and the wear track. The huge solid transfer layer not only makes a wear-resistant contact interface between the transfer layer and the underlying film by densification and oxidation, but also reduces surface interaction energies, finally resulting in a significant improvement in durability.

graphene oxide (GO)↗
DOE OSTI2024

Comparison of Eco-Friendly Ionic Liquids and Commercial Bio-Derived Lubricant Additives in Terms of Tribological Performance and Aquatic Toxicity

Approximately half of the lubricants sold globally find their way into the environment. The need for Environmentally Acceptable Lubricants (EALs) is gaining increased recognition. A lubricant is composed of a base oil and multiple functional additives. The literature has been focused on EAL base oils, with much less attention given to eco-friendly additives. This study presents the tribological performance and aquatic toxicity of four short-chain phosphonium-phosphate and ammonium-phosphate ionic liquids (ILs) as candidate anti-wear and friction-reducing additives for EALs. The results are benchmarked against those of four commercial bio-derived additives. The four ILs, at a mere 0.5 wt% concentration in a synthetic ester, demonstrated a 30–40% friction reduction and >99% wear reduction, superior to the commercial baselines. More impressively, all four ILs showed significantly lower toxicity than the bio-derived products. In an EPA-standard chronic aquatic toxicity test, the sensitive model organism, Ceriodaphnia dubia, had 90–100% survival when exposed to the ILs but 0% survival in exposure to the bio-derived products at the same concentration. This study offers scientific insights for the future development of eco-friendly ILs as lubricant additives.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Quality Control Metrics to Assess MoS2 Sputtered Films for Tribological Applications

Abstract Pure molybdenum disulfide (MoS 2 ) solid lubricant coatings could attain densities comparable to doped films (and the associated benefits to wear rate and environmental stability) through manipulation of the microstructure via deposition parameters. Unfortunately, pure films can exhibit highly variable microstructures and mechanical properties due to processes that are not controlled during deposition (i.e., batch-to-batch variation). This work focuses on developing a relationship between density, hardness, friction, and wear for pure sputtered MoS 2 coatings. Results show that dense films ( ρ = 4.5 g/cm 3 ) exhibit a 100 × lower wear rate compared to porous coatings ( ρ = 3.04–3.55 g/cm 3 ). The tribological performance of high density pure MoS 2 coatings is shown to surpass that of established composite coatings, achieving a wear rate 2 × ( k = 5.74 × 10 –8 mm 3 /Nm) lower than composite MoS 2 /Sb 2 O 3 /Au in inert environments.

Babuska, Tomas F.↗
DOE OSTI2025

Methods to Observe Tribological Failures in Self-Mated Steel Contacts

Scuffing, a type of wear found in highly stressed or poorly lubricated contacts, is characterized by a rapid increase in friction and severe plastic deformation of the near-surface material. Scuffing has proven difficult to study because it initiates unpredictably, progresses rapidly, and typically develops within an inaccessible contact interface. Although there have been successful in-situ studies of scuffing in real-time, the transparent counter body needed for these studies changes the interactions between the surfaces and the lubricant, which affects the scuffing process in unknown ways. This paper describes the development of X-ray-compatible tribometry to study the scuffing of self-mated steels in-situ and in real-time. The method uses a crossed cylinders configuration with a thin (500 μm thick) stationary component and a small (≈200 μm) contact width to maximize X-ray interactions with atoms within the stress field generated by the contact. The resulting instrument and method are used to benchmark the scuffing response of self-mated 52,100 steel under tribologically challenging ‘oil-off’ lubrication conditions. The results demonstrate reliable scuffing in this configuration despite the relatively small contact areas and loads used. Following scuffing, gross plastic deformation was observed on both surfaces along with significant subsurface grain refinement and flow only on the stationary surface, which experienced constant contact. Interestingly, high friction initiated at specific locations of the migratory surface, which experienced intermittent contact, and then propagated across the track over time, suggesting that local conditions of the migratory surface dominated friction leading into the failure event.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Tribological properties of PDA + PTFE coating in oil-lubricated condition

In this work the tribological properties of 45 ± 2 μm-thick polytetrafluoroethylene (PTFE) and polydopamine (PDA) + PTFE coatings in oil-lubricated conditions were investigated under a normal load of 10 N and a linear reciprocating speed of 0.1 m/s. Both the PTFE and the PDA + PTFE coatings were deposited using an in-house spray-coating method. The PDA + PTFE coating was five times more durable compared to the PTFE coating in oil-lubricated conditions. Both PTFE and PDA + PTFE coatings showed lower COF in oil-lubricated conditions than in dry conditions. The nanomechanical properties measured by PeakForce Quantitative Nanomechanical (PFQNM) characterization method showed an increase in Young’s modulus and adhesion force for the PDA + PTFE coatings compared to the PTFE coatings. Chemical analysis showed that the cross-linking between PDA and PTFE polymer chains occurred during the high-temperature sintering procedure. Finally, the higher adhesion of PDA + PTFE coating to the cast iron substrate and the stronger cohesion due to the cross-linking between PDA and PTFE contributed to the higher durability of the PDA + PTFE composite coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A novel fiber-fretting test for tribological characterization of the fiber/matrix interface

Ceramic matrix composites exhibit excellent high temperature properties and are candidate materials for structural applications from jet engines to nuclear fuel cladding. The strength and deformation behavior of these composites are intrinsically tied to the properties of the fiber/matrix interface. This research introduces a novel technique to evaluate the fundamental friction and wear characteristics of these interfaces. A case study on SiC f /PyC/SiC m composites applies in situ fiber fretting to investigate the kinetic friction coefficient and cyclic wear characteristics of the interphase. The experimental methodology is presented in explicit detail to encourage other researchers to explore the capabilities of this technique. Additionally, testing was carried out as a function of fiber roughness, PyC thickness (≈10, 500, 1200 nm), cycle count (10, 100, 1000), and frequency (1, 5, and 10 Hz). The friction coefficient and wear behavior changed with cycle length due to a transition from adhesive to abrasive mechanisms. SEM fractography provided insights to tribological evolution from adhesive sliding to three-body abrasive wear. The structural disorder at the tribo-surface relating to graphitic content and dangling bond density was investigated using Raman spectroscopy. Properties are contextualized with comparison to uniaxial tensile behavior of the parent composite.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Tribological behavior of ceramic-alloy bearing contacts in molten salt lubrication for concentrating solar power

Molten salts are considered as candidate heat transfer fluids and thermal energy storage media for next generation concentrating solar power (CSP). A molten salt circulates inside the piping and heat exchanger and also functions as a lubricant for the sleeve bearings of the CSP pump. Furthermore, wear- and corrosion-resistant high-temperature bearing materials are critical for the pump efficiency and durability. This study evaluated the tribological performance of candidate bearing materials in lubrication of a molten chloride salt mixture (20% NaCl + 40% MgCl 2 + 40% KCl) at 750 °C in an inert argon gas (a simulative CSP pump environment). Six ceramic-alloy pairs were tested, zirconia and silicon nitride against Haynes 244, Hastelloy C276, and Tribaloy T900 alloy, and ranked by the friction coefficient and wear loss. Characterization of worn surfaces suggested the wear mechanism as a combination of abrasion, adhesion, and tribocorrosion. Results from this study provide fundamental insight for the development and selection of bearing materials for molten salt powered CSP pumps.

14 SOLAR ENERGY↗
DOE OSTI2021

Post weld heat treatment and operating temperature effect on tribological behavior of laser cladded stellite 21 coating

This study intends to investigate the feasibility of using laser cladding as a potential process to repair hot working tools by a hardfacing process. A Stellite 21 alloy coating was printed on a 350 maraging steel via laser cladding and the coating microstructure and tribological performance were characterized in as printed conditions and after heat treatment. Such a laser-processed coating showed a high integrity with little porosity and good bonding with the substrate. The Stellite coating produced substantially lower friction and a smoother contact area but had inferior wear resistance compared with the maraging steel substrate. Post process heat treatment at 650 °C for 20 h led to significant amount of strain-induced FCC to HCP phase transformation but had little improvement in wear resistance. Detailed materials characterization using X-ray diffraction and electron microscopy provided fundamental insights to the underlying mechanisms. This study opens the door for future R&D for tool surface repair by laser cladding.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Tribological behavior of nuclear graphite in high-temperature inert environment

This report formally documents the completion of the Advanced Reactor Technologies Level 2 Milestone (M2AT-26OR0605058), “Complete initial wear/abrasion studies,” due June 1, 2026. The work presented in this report expend upon our previously published manuscript titled Sliding friction and wear behavior of nuclear graphite in high temperature inert environment: Influence of contact load, speed and temperature. The sliding friction and wear of self-mated ET-10 nuclear graphite were characterized across a range of elevated temperatures (650°C and 750°C), contact loads (20 N and 40 N), and sliding speeds (1 mm/s and 10 mm/s) within a controlled argon environment. Tribological data combined with advanced morphological characterization were used to provide a detailed mechanistic framework for the frictional and wear behavior of nuclear graphite in high-temperature inert conditions. Furthermore, the report evaluates the inherent limitations of bench-scale characterization and addresses the critical disparities between laboratory findings and the complex, in-service friction and wear behavior of fuel pebbles within a reactor environment.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mucus-Inspired Tribology, a Sticky Yet Flowing Hydrogel

The mucus blanket can trap foreign particles before they enter the lungs, while at the same time, it flows up to remove these particles. This manifests the dual nature of mucus: sticky, on one hand, and fluid, on the other. Inspired by this function of mucus in the lungs, we designed a mucus simulant which emulates this dual nature. While many existing mucus simulants do not target bioadhesion particularly, poly(vinyl alcohol) (PVA)-based simulants make an exception. Despite their bioadhesion tendency, unlike mucus, they do not gelate. In this study, we added a physical cross-linking agent to PVA in order to add the gelation aspect and to better represent mucous properties. We show that the resultant mucus simulant develops into two regions: a highly sticky region near the surface of a foreign object (we used hydrophobized silicon to mimic the foreign object) and a fluid region far away from that surface. We show that the sticky part can slide past the less sticky part, while the foreign object is stuck to it. However, this mechanism changes with time. At short gelation times, this tendency to separate into two parts is enhanced and the foreign object remains stuck, while the rest of the gel flows. With time, the force required to allow the sticky part to slide over the fluid part is further reduced. However, if the gelation is allowed to proceed for even longer times without disturbance, the force required to slide the two parts past each other increases and the separation between the two parts is inhibited. The hydrogel becomes a sticky goo, which requires a higher force to move or unclog if placed in a duct (much like what happens with mucus in the tracheal duct). We explain the physics of our findings in terms of a competition between the tendency of the polymer to form a gel network and the tendency of the polymer to adsorb onto the foreign object.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthetic Lubricants Derived from Plastic Waste and their Tribological Performance

The energy efficiency, mechanical durability, and environmental compatibility of all moving machine components rely heavily on advanced lubricants for smooth and safe operation. Herein an alternative family of high-quality liquid (HQL) lubricants was derived by the catalytic conversion of pre- and post-consumer polyolefin waste. The plastic-derived lubricants performed comparably to synthetic base oils such as polyalphaolefins (PAOs), both with a wear scar volume (WSV) of 7.5×10 -5 mm -3 . HQLs also performed superior to petroleum-based lubricants such as Group III mineral oil with a WSV of 1.7×10 -4 mm -3 , showcasing a 44% reduction in wear. Furthermore, a synergistic reduction in friction and wear was observed when combining the upcycled plastic lubricant with synthetic oils. Additionally, life cycle and techno-economic analyses also showed this process to be energetically efficient and economically feasible. This novel technology offers a cost-effective opportunity to reduce the harmful environmental impact of plastic waste on our planet and to save energy through reduction of friction and wear-related degradations in transportation applications akin to synthetic oils.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗