Search results

In electronic packaging, when solid copper comes in contact with liquid solder alloy, the former dissolves and intermetallic compounds (IMCs) form at the solid‐liquid interface. The purpose of this paper is to study the effect of the presence of molybdenum nanoparticles on the dissolution of copper and the formation of interfacial IMC.

Cu wire having a diameter of 250 μm is immersed in liquid composite solders at 250°C up to 15 min. Composite solder was prepared by adding various amount of Mo nanoparticles into the Sn‐3.8Ag‐0.7Cu (SAC) solder paste. The dissolution behavior of Cu substrate is studied for SAC and Mo nanoparticles added SAC solders. The IMCs and its microstructure between the solder and substrate are analyzed by using conventional scanning electron microscope (SEM) and field emission SEM. The elemental analysis was done by using energy‐dispersive X‐ray spectroscopy.

Generally, the dissolution of the substrate increases with increasing immersion time but decreases with the increase of the content of Mo nanoparticles in the solder. The IMC thickness increases with increasing the reaction time but Mo nanoparticles can hinder the growth of IMC layer. The presence of Mo nanoparticle is found to be effective in reducing the dissolution of copper into SAC solder.

The paper shows that molybdenum nanoparticles in liquid SAC solders have a prominent effect on the substrate dissolution rate and the interfacial IMC between the SAC solder and copper substrate.

Experiments were carried out on the load‐carrying capacity and the endurance under light loading of five dry surface treatments. It was found that molybdenum di‐sulphide, rubbed or bonded on to mild steel, gave little effective protection against seizure. The combination of a phosphating treatment with an applied lubricant resulted in a good bearing surface. Of the three additional lubricants tested, a bonded coating of molybdenum di‐sulphide was superior to a coating of paraffin wax, which was itself superior to a coating of molybdenum di‐sulphide rubbed on.

The resistance to stress corrosion cracking of austenitic stainless steels has been investigated and discussed with respect to the influence of molybdenum.

TO make alloy steel we draw almost entirely upon material from outside the United States. We produce our own molybdenum. Our nickel comes from Canada and so does a part of our copper. Manganese and chromium are nearly all imported. We produce some tungsten and substantial amounts of vanadium. Tin, columbium and other vital materials are imported.

MOLYBDENUM wire, as a coating material, is well known since molybdenum has many advantages as a hard bearing surface; it is highly scuff‐resistant and has a low coefficient of friction. Metco now announce a self‐fusing, high‐molybdenum powder which can be plasma flame sprayed to produce tough, wear‐resistant coatings on many types of base materials, and in thicknesses ranging from 0–1 to 3 mm.

This paper aims to focus on the potential for substituting molybdenum‐based piston ring coatings, which are recognized as “allrounder” by other candidate metallurgies. Another purpose is the tribological interaction of molybdenum‐based and new triboactive/reactive piston ring coatings with low SAP, polymer‐ and metal‐free as well as bionotox engine oils with high‐viscosity indices.

Substoichiometric titanium dioxide composed of the Magnéli‐types phases Ti₄O₇ (∼17 per cent), Ti₅O₉ (∼66 per cent), Ti₆O₁₁ (∼17 per cent) deposited by plasma spraying, a vacuum sprayed TiO_1,93 and a plasma‐sprayed titanium‐molybdenum carbo‐nitride coated piston rings were compared to a state‐of‐the‐art molybdenum‐based piston ring. They were tribologically characterized by means of BAM and SRV tests lubed under mixed/boundary lubrication by factory fill engine oils, engine oils as blends of hydro‐carbons with esters as well as prototype engine oils based on esters and polyglycols.

Overall, the molybdenum‐ and titanium‐based ring coatings wore in the same order of magnitude. The ranking depends on the test used. The BAM test favours MKP81A (PL72) more, whereas the SRV methods favour the Ti_nO_2n−1 more. The different bionotox and low‐ash prototype engine oils with reduced additive contents displayed isoperformance regarding the tribological behaviour of common and triboreactive materials. They presented no visible weakness in wear resistance, coefficient of friction and extreme pressure properties.

The next steps have to confirm functional properties by different engine and endurance tests.

Titanium‐based piston ring coatings are overall more attractive, as they are primarily refined from titania, which is cheap and not rated at stock exchanges, and they present at least an isoperformance when compared with molybdenum‐based ring coatings.

This supplier report displays the complete methodology in order to substitute molybdenum‐ by titanium‐based piston ring coatings as well as illuminating the beneficial interaction with alternative engine oils in existing engine architectures.

The aims of this study is to analyze failure of two types of high‐strength low‐alloy (HSLA) steels which are used in wheel bolts 10.9 grade, boron steel and chromium‐molybdenum steel, before and after heat treatment.

The optimum heat treatment to obtain the best tensile behavior was determined and Charpy impact and Rockwell hardness tests were performed on the two steel types before and after the optimum heat treating.

Fractographic studies show a ductile fracture for heat‐treated boron steel while indicate a semi‐brittle fracture for heat‐treated chromium‐molybdenum steel. Formation of a small boron carbide amount during heat treating of boron steel results in increment the bolt's tensile strength while the ductility did not changed significantly. In the other hand, formation of chromium and molybdenum carbides during heat treating of chromium‐molybdenum steel increased the bolt's tensile strength with a considerable reduction in the final ductility.

This paper evaluates failure analysis of HSLA wheel bolt steels and compares their microstructure before and after the loading regime.

This paper is a summary of the work done at Rock Island Arsenal on additives for greases. It covers antioxidants, antiwear and extreme pressure agents and rust preventive additives. No attempt is made to list the results of all additives tested. Instead the additives are divided into groups of related compounds and the results of typical, ones given. A general evaluation of each group as a whole is given, Classes of compounds which proved good as antioxidants were metal dithiocarbamates, amino‐phenyl ethers, phenylene‐diamines, methane derivatives and certain hindered phenols and di‐substituted amines. The temperature barrier was the major obstacle for the anti‐oxidants and only 9 of the 100 or so which were effective at 21()°F, were equally effective at 250°F. Sulfur, chlorine, and lead‐containing additives were the best for extreme pressure improvement. Those containing only phosphorous were belter for antiwear. Improvements in both properties could be obtained by mixing the additives. Improvement in either property seemed to depend, more upon the type of compound than upon the responsible element. For example, all sulfur containing compounds were not equal in extreme pressure properties. Some of the antiwear and extreme pressure additives were tested for their ability to reduce fretting corrosion. Results indicate that sulfur containing compounds reduce fretting while, compounds containing only phosphorous increased it. Results are given which indicate that molybdenum disulfide added to greases is detrimental to wear at lower loadings. It does improve the extreme pressure abilities of the grease. Us presence in a grease increases the rusting tendencies of greases unless an antirust agent is also present.

The effects of space environment on friction and wear and on the selection of lubricants and self‐lubricating materials for spacecraft mechanisms are discussed, with special emphasis on the ultrahigh vacuum of space. Experimental studies have demonstrated the feasibility of using selected oils and greases to lubricate lightly loaded ball bearings without replenishment for periods of over one year under the following conditions of operation : speeds of 8,000 rpm, temperatures of 160 to 200°F., and vacuum of 10–8 torr. Over one‐half year of successful operation has been achieved under similar operating conditions with self‐lubricating retainers of reinforced Teflon, provided that the loads were light. Bonded films of molybdenum disulfide have given shorter lifetimes and poor repro‐ducibility. Metal‐to‐metal slip‐ring contacts introduce excessive electrical noise into circuits when operated in vacuum of 10–7 torr. The noise (as well as the friction and wear) can be markedly reduced by providing a small amount of oil vapor, sufficient to maintain a pressure on the order of 10–6 torr, or by incorporating molybdenum disulfide into the brush material.

The thermal management of printed circuit boards with high component density is increasingly becoming an important factor in the efficiency and reliability of electronic systems. A well‐proven technique, which has been used to produce multilayer circuit boards in quantity for several years, is to incorporate metal foils. The metal foils significantly improve heat removal and impart to the circuit board a thermal expansion behaviour closely matching that of the ceramic chip carrier. Roll‐clad Copper‐Invar‐copper (CIC) and copper‐molybdenum‐copper (CMC) foils have been used for this purpose. This paper reports on the first use of Mo30Cu foils, a material produced by powder metallurgy consisting of 70% molybdenum and 30% copper. Contraves AG manufacture SMT multilayer circuit boards incorporating Mo30Cu foils produced by Metallwerk Plansee GmbH. With regard to machinability and physical characteristics, Mo30Cu foils are superior to roll‐clad foils. First of all, the high elastic modulus of Mo30Cu foils is worth mentioning. It positively influences thermal stability and mechanical stiffness of the circuit board.