Wright, Peter


Table 4. Chemical Composition of Wrought and Powder Nickel-Base Superalloys, wt % Table 4. Chemical Composition of Wrought and Powder Nickel-Base Superalloys, wt %
Powder Metallurgy of Superalloys. In addition to providing improved yields and efficiencies, powder metallurgy allows higher alloying additions ia wrought products because of reduced segregatioa, and therefore superplastic stmctures are readily achieved. This is a significant factor ia enabling superaHoys which are heavily aHoyed to provide superior mechanical properties and oxidation and corrosion resistance for rotating parts exposed to high operating temperatures ia aircraft turbiae engines.  [c.239]

Because the ductiUty of molybdenum is adversely affected by even minute amounts of oxygen, stringent precautions must be taken to prevent it from being present during fusion welding. Inert gas atmospheres must be as free of oxygen as possible. Commercial argon, helium, and hydrogen may contain oxygen levels which can cause cracking and porosity unless specific purification measures are provided. Thorough cleaning of the faying surfaces is essential for optimum ductihty. Such surfaces have usually become contaminated during prior processing and handling. Wrought arc-cast molybdenum can be welded with less difficulty than powder metallurgy products because the arc-cast metal has been out-gassed and deoxidized during melting.  [c.466]

Terpene Resins" in ECT 1st ed., VoL 13, pp. 700—704, by W. J. Roberts and A. L. Ward, Peimsylvania Industrial Chemical Corp. "Terpenes and Terpenoids" in ECT 1st ed., Vol. 13, pp. 705—771, by R. S. Ropp, Hercules Powder Co. J. E. Hawkins, University of Elorida, E. G. Reitz, Chicago City Colleges (Wright Branch), P. de Mayo, Birkbeck College, University of London, and G. C. Harris, Hercules Powder Co. in ECT 2nd ed., Vol. 19, pp. 803—838, by S. J. Autenrieth and A. B. Booth, Hercules Incorporated "Camphor" in ECT 2nd ed., Vol. 4, pp. 54—58, by G. Etzel, Camphor AUied Products Ltd. "Terpenoids" in ECT 3rd ed., Vol 22, pp. 709—762, byj. M. Derfer and M. M. Derfer, SCM Corp.  [c.431]

Cast and Wrought Forms. Thousands of tons of tin ingots are cast into anodes for plating processes. Tin foil is used for electrical condensers, botde-cap liners, gun charges, and wrappings for food. Tin wine is used for fuses and safety plugs. Extmded tin pipe and tin-lined brass pipe are the first choice for conveying distilled water and carbonated beverages. Sheet tin is used to line storage tanks for distilled water. Tin powder is used in powder metallurgy, the largest use going to tin powder mixtures with copper to form bronze parts. It is also used for coating paper and for solder pastes.  [c.60]

Beryllium and aluminum are virtually insoluble in one another in the soHd state. The potential therefore exists for an aluminum—beryllium metal matrix composite with lower density and higher elastic modulus, ie, improved specific modulus, than conventional aluminum alloys produced by ingot or powder metal processing. At least one wrought composite system with nominally 62 wt % Be and 38 wt % A1 has seen limited use in aerospace appheations (see Composites).  [c.73]

The chemical and physical properties of some metals and alloys, such as hardness, strength, stiffness, toughness, corrosion resistance, and biocompatibility have provided materials capable of withstanding the most severe demands of restorative dentistry, namely the harsh corrosive environment of the mouth and high stresses on the small cross-sectional areas of teeth. Metallurgical and dental science have given dentistry many excellent alloys for restorative dentistry, prosthetic dentistry, orthodontics, and dental techniques. These alloys iaclude amalgams base metal alloys such as cobalt—chromium casting alloys (for partial dentures), chromium-containing casting alloys (for crowns and bridges), and titanium alloys (for implants, partial dentures, crowns and bridges) gold and gold alloys, ie, foil, crystal powder, Au—Ca alloy combinations for casting and wrought alloys platinum and platinum alloys solders, ie, gold solders, silver solders, and special solders and electrodeposited metals such as copper and silver. An excellent review on metals and alloys in dentistry is available (129).  [c.481]

A tandem arrangement of two DNA-binding domains, called the POU region, is present in a class of transcription factors involved in development and in the expression of growth factors, histones and immunoglobulins. The POU region is a 150-160 amino acid sequence consisting of a homeodomain and a POU-specific domain joined by a short variable linker region (Figure 9.13). NMR studies by the groups of Robert Kaptein in Utrecht University and Peter Wright at The Scripps Research Institute, La Jolla, established that the POU-specific domain has a structure very similar to the X repressor, in spite of having no apparent sequence homology as described in Chapter 8, this structure is very simple, consisting of four a helices where helices 2 and 3 form a helix-turn-helix motif. The POU region has, therefore, two helix-turn-helix motifs that are similar while the remaining structures of its two domains are quite different.  [c.164]

Since gases have smaller MIEs than dusts, they represent the more challenging case for grounding. The most challenging case is where powders and flammable gases are handled together in air, combining the high charging rates produced by powder flow with the small MIE of flammable gases. Eor simple capacitance sparks, the MIE of gases decreases as storage capacitance and electrode tip diameter are decreased (Eigure 3-5.4.1). The required resistance to ground can be found by considering the worst credible case flammable mixture, storage capacitance and electrode diameter. As shown in A-4-1.3 a ground resistance criterion can be written in terms of MIE  [c.72]

While it is relatively easy to remove volatile solvents such as ethyl ether and acetone during a drying process, less volatile solvents may persist at about 1 wt% or more in the product. The rate of evolution of solvents may be a slow process and difficult to estimate without practical testing. The worst case can be determined for a closed container at the highest anticipated temperature. For example, the temperature in a shipping container can be measured using a maximum-minimum thermometer so that the maximum transit temperature is found. This might exceed 50°C. Closed container evolution tests on a fresh powder sample can then be done to determine the maximum gas concentration that can develop. If this exceeds about 50% of the gas LFL, there is the potential for sensitized hybrid dust-gas mixtures. A separate problem would arise should the maximum gas concentration approach the LFL, which could indicate a gas ignition risk in the container. Tests have shown that powders containing upward of 0.2-0.5wt% solvent should be evaluated for these hazards. A possible solution, short of higher efficiency drying or extended powder storage in a ventilated area prior to shipment, is to use a high ventilation shipping container or ventilated hopper car. Special attention should be given to avoiding flammable gas evolution from powder packages that might be air shipped. A separate issue is powders that evolve flammable gas via ongoing reaction such as with atmospheric moisture (eg some metal alkoxides) or degradation of peroxides in the formulation. While the hybrid mixture hazards are similar to those with solvent-containing products, the source of flammable gas is in such cases renewable, and precautions need to be taken throughout the handling process. In all cases attention should be given to the possibility of gas concentrations markedly increasing with increased time and temperature. For example, a gas sample taken from a hopper car might underestimate the gas concentration that develops after shipment to a customer. Similarly, the gas concentration might increase after transfer to a powder silo heated in sunlight.  [c.173]

If a powder has been characterized by a particular MIE, say 10 mJ, this does not mean a typical suspension in air has a MIE of 10 mJ. MIE tests are made on either sub-200 mesh dust or finer fractions designed to represent the worst credible case (6-1.2). The reported MIE corresponds to the optimum concentration of this fine dust fraction in air, which is relatively large and often difficult to achieve in practical operations, being typically in the range 250-750 g/m. Estimates of the effective energy of bulking brush discharges, based on accident analyses, indicate a maximum value of 10-20 mJ, or less than the MIE of Lycopodium (20 mJ). Since the effective energy exists as a distribution of possible values up to the maximum value, most discharges will have only a fraction of the maximum effective energy. The probability of ignition is extremely small for dusts with MIE similar to Lycopodium and negligible for dusts with significantly greater MIEs. Since the ignition frequency for most dusts is very small, it is common practice to provide only  [c.195]

If a powder is capable of evolving flammable vapor at or above its LFL it should be considered as being handled in a flammable vapor atmosphere (6-7.3). This hazard may be present if the powder is reactive (slowly decomposes or reacts with moisture forming flammable vapor) or contains upward of 0.2 wt% of flammable solvent. Evaluation of a vapor hazard may require closed container testing over an extended period at a sufficiently high temperature to represent worst-case storage conditions. This may be several weeks at 50-60°C in some cases. If the vapor concentration can attain greater than 50% of its LFL the combination of vapor plus suspended dust may result in an easily ignitable hybrid mixture which should be considered equivalent to a flammable vapor atmosphere. Types A and B should not be used in flammable vapor atmospheres. For direct transfers to flammable liquids see 6-7.2.  [c.199]

Conventional Wrought nd C st Alloys. The nickel-base superaHoys are the most complex in composition and microstmctures and, in many respects, the most successful high temperature aHoys. Development commenced in the late 1930s with the need for aircraft gas turbine component materials that were stronger than the then-available austenitic stainless steels. The earhest superaHoys were wrought, ie, fabricated to final size by a mechanical working operation. The earhest superaHoy (Nimonic 75) was produced by adding 0.3% Ti and 0.1%C to an oxidation resistant soHd solution 80%Ni—20%Cr (Nichrome) base. Higher engine speeds and turbine inlet temperatures were the impetus for succeeding modifications, first by adding aluminum and titanium to produce strengthening (Nimonic 80), and later by adding cobalt to raise the volume fraction of y and to improve workabHity (Nimonic 90). Later aHoys have incorporated higher aluminum plus titanium contents, as weH as molybdenum for soHd-solution strengthening (Nimonics 115 and 120). The compositions of these and other wrought nickel-base aHoys are Hsted in Table 4. Also included are compositions of some powder processed aHoys.  [c.119]

OU quenching and tempering at 230°C, for example, produces tensile strengths of ca 1.5 GPa (215,000 psi) (ultimate) and ca 1.25 GPa (185,000 psi) (5aeld) with 7% elongation and RC 43 hardness (qv). Heat treating at 650°C reduces strength and hardness values by 50% but triples elongation. The cups and cones for tapered roUer bearings are forged from grade 4600 powder (2 wt % nickel, 1/2 wt % molybdenum alloy), which corresponds to AISI 4600 grade steel. These perform at least equal to and up to eight times longer than the same part produced from wrought steel.  [c.184]

A processing technique introduced in the late 1960s involves atomization of the prealloyed molten tool steel alloy into fine powder, followed by consohdation under hot isostatic pressure (HIP) (20—23). This technique, termed consoHdation by powder metallurgy (CPM), when combined with suitable hardening and tempering, provides a microstmcture consisting of a uniform and fine dispersion of carbides in a fine-grained, tempered, martensite matrix. For example, a mean of 1.3 p.m and a maximum of 3.5 pm for carbide grain size results from CPM compared to a mean of 6.2 pm and a maximum of 34 pm by conventional cast and wrought processes. Tool steels made in this manner grind more easily, especially the highly alloyed tool steels, with grinding ratios two to three times better exhibit more uniform properties and perform more consistently (24). Also, highly alloyed tool steels that can attain HRC 70 caimot be made by the conventional casting or hot forming processes but can be made by CPM. Because of the fine size of the carbides present in tool steels made by CPM, tools made of this material have significant edge strength and provide edge sharpness during cutting, such as in end milling. Consequently, material made by this process is extensively used to produce relatively inexpensive tools, such as drills, milling cutters, and taps, as well as expensive form tools such as broaches, shaper cutters for gears, and various dies for metal forming appHcations. Tool steels up to HRA of 70 can be obtained using high Co (up to 20%) and high vanadium carbide (VC) (also up to 20%). This would, however, be at the expense of significant loss of toughness. Tool steel technology has matured. Improvements in cleanliness of tool steels, ie, control of the composition of tramp elements, and tighter tolerances on the chemical composition, etc, are underway, as is improvement in the overall quality of the product.  [c.199]

Beryllium sheet is produced by rolling powder metallurgy billets clad in steel cans at 750—790°C. Beryllium foil down to 12.5 p.m (0.0005 in.) in gauge is commercially available. Extmsion is also carried out in this temperature region, again using steel cans to contain the powder metallurgy billet. Working of beryUium results in the estabUshment of a high degree of preferred crystallographic orientation, generally enhancing the properties in the direction of working, but impairing properties normal to the working direction. This is particularly tme for tensile elongation. Cross-rolling schedules ate followed in rolling that ensure good tensile elongation in the plane of the sheet (10% minimum by specification and 20% is not unusual), but the strain capacity in the thickness direction is limited. The preferred orientation problem has limited the use of wrought beryUium many shapes other than common stmcturals ate usually machined from bUlets where standard metaUurgical practice with other metals would involve toUed, extmded, or forged components.  [c.68]

Gold and Gold Alloys. Gold foil, crystal powder, a gold-calcium alloy, and combkiations thereof ki the noncohesive states are used ki dentistry as direct-filling materials an adsorbed layer of ammonia renders the gold noncohesive for packagkig, and heating returns it to a cohesive state for use. Gold alloys are used for cast restorations and prosthetic devices. Wrought gold alloys are used for wke clasps and fabricated orthodontic appHances (see Gold and gold compounds).  [c.482]

A granule is a nonuniform physical composite possessing certain macroscopic mechanical properties, such as a generally anisotropic-yield stress, as well as an inherent flaw distribution. Hard materials may fail in tension (see brittle fracture under size reduc tion), with the breaking strength being much less than the inherent tensile strength of bonds because of the existence of flaws. [Lawn, Fracture of Brittle Solids, 2d ed., Cambridge University Press (1975).] Bulk breakage tests of granule strength measure both the inherent bond strength of granule as well as its flaw distribution. [Bemros Bridgwater, Powder Tech., 49, 97 (1987).] In addition, the mechanism of granule breakage (Table 20-39) is a strong func tion of materials properties of the granule itself as well as the type of loading imposed by the test conditions. Ranking of produc t-breakage resistance by ad hoc tests may be test specific, and in the worst case differ from actual process conditions. Standardarized mechanical tests should be employed instead to measure material properties which minimize the effec-t or flaws and loading conditions under well-defined geometries of internal stress, as described below.  [c.1886]

Ignition Testing for Conductive and Antistatic FIBCs FIBC testing has been carried out using a grounded metal test probe held in a tube containing a flammable hydrocarbon-air test mixture (typically ethane or propane in air). The probe arrangement is typically brought to the external surfaces of the FIBC during filling or emptying operations. However, since powder transfer might be made to methanol which has about half the MIE of propane (Appendix B), it is recommended that ethylene at its most easily ignitable composition be used to simulate flammable vapor atmospheres rather than aliphatic hydrocarbons. Since ethylene has a very small MIE relative to common solvents, this offsets limitations in the number of tests that can reasonably be done and the probability that worst case conditions will not be realized under test conditions (3-8.1).  [c.202]


See pages that mention the term Wright, Peter : [c.436]    [c.177]    [c.171]    [c.704]    [c.402]   
Introduction to protein structure (1999) -- [ c.164 , c.177 ]