What is the difference between lithium grease and calcium grease?5 answersLithium grease and calcium grease differ in their performance characteristics. Lithium complex greases, commonly used in industrial applications, have been the traditional choice due to their versatility and widespread use in bearings under high loads and speeds. However, calcium sulfonate greases have shown superior performance in extreme pressure conditions, with the ability to withstand higher contact pressures without seizure wear. Additionally, calcium sulfonate complex greases exhibit better abrasion resistance and load-bearing properties compared to lithium complex greases, making them more effective in lubrication at high temperatures and under heavy loads. The formulation of lithium complex-calcium sulfonate greases in different ratios allows for adjustability in physicochemical and tribological properties, with a 1:2 ratio showing the best lubrication function due to synergistic lubrication mechanisms.
What is the effect of Ca on Mg corrosion?5 answersThe addition of Ca to Mg alloys has been found to have a positive effect on corrosion resistance. The presence of Ca refines the grain structure of the alloys and leads to the formation of protective corrosion product films. The refinement of the grain structure and the formation of protective films contribute to the reduction of corrosion rates in various electrolytes, such as NaCl and Na2SO4. The addition of Ca also introduces new phases, such as Ca2Mg6Zn3, which further enhance the corrosion resistance of the alloys. Overall, the presence of Ca in Mg alloys improves their corrosion resistance by refining the grain structure, forming protective films, and introducing new phases.
Does the wear properties increase by reducing the friction coefficient in magnesium alloy?5 answersThe wear properties of magnesium alloy can be improved by reducing the friction coefficient. Studies have shown that with the decrease of extrusion temperature, the surface hardness increases and the friction coefficient decreases, leading to improved wear resistance. Alloying-extrusion-aging treatments have also been found to effectively inhibit the formation of plastic deformation layers, resulting in lower wear rates. Additionally, the addition of rare earth metal Sc has been shown to decrease the friction coefficient and reduce weight loss, enhancing the wear resistance of magnesium alloys. Cryogenic milling has been found to contribute to the formation of a corrosion-resistant second phase in magnesium alloys, resulting in better tensile strength, elongation, and reduced friction coefficient and wear amount. However, it should be noted that while reducing the friction coefficient can improve wear properties, it may not necessarily eliminate wear altogether, as abrasive wear has been observed in dissolvable magnesium alloys with lower friction coefficients.
How can calcium protect surface from corrosion?3 answersCalcium can protect surfaces from corrosion by forming a protective layer on the surface. This layer acts as a barrier, preventing corrosive substances from reaching the underlying metal. The calcium oxide/phosphorus pentoxide glass system, when in contact with water, releases phosphate ions that inhibit corrosion of adjacent metal surfaces. In the calcium aluminosilicate glass system, the reactivity of the glass surfaces depends on the relative amount of alumina in the bulk. The attack of Al-O bonds and release of calcium are the primary modes of degradation in acidic solutions. Calcium nitrite can be used as an admixture in concrete to inhibit the corrosion of steel reinforcing rebars in chloride-contaminated environments. Coating the surface of an inorganic material containing calcium, such as reinforced concrete, with a solution containing a fluorophosphate and a nitrite can improve its durability and maintain the reinforcing bar in a rust-proof state. Overall, calcium can protect surfaces from corrosion through the formation of protective layers and the release of inhibiting ions.
How does calcium ion concentration affect oil recovery?5 answersCalcium ion concentration has been found to affect oil recovery. In the presence of calcium ions, the interfacial tension between crude oil and surfactant solution at low salinity can be further reduced by 1-2 orders of magnitude, resulting in improved oil recovery. Additionally, the ion composition of smart water, which includes calcium ions, has been shown to affect oil recovery during smart waterflooding. Low concentrations of calcium ions, along with low concentrations of magnesium ions, have been found to result in the highest oil recovery factor. Furthermore, the presence of calcium ions in the smart water composition during flooding experiments has been observed to trap more oil and create larger residual oil clusters, indicating a shift towards (weakly) water-wet conditions. These findings suggest that calcium ion concentration plays a significant role in altering wettability and improving oil recovery.
What are the tribological properties of the new material?2 answersThe tribological properties of the new materials investigated in the provided abstracts vary. The sintered steel materials coated with DLC showed increased resilience to wear and resistance to contact fatigue. The combination of multilayer graphene (MLG) and WS2 exhibited excellent tribological properties, with a continuous lubricating film reducing friction coefficient and wear rate. The Fe3Al material sliding against Si3N4 ceramic ball showed a wear rate in the orders of 10^-4 mm^3 m^-1, with increasing load and sliding speed leading to a transformation in the wear mechanism. Carbon-rich metal/carbon coatings of chromium, tungsten, and titanium showed a strong dependence on composition for their tribological properties, with the three-body wear resistance of tungsten carbon compounds correlating with Vickers hardness.