18G Gauje and R Morbioli High Temperature Protective Coatings SS Singhal Ed The
19. R.S. Parzuchowski, U.S. Patent 4,132,816, 1979 Principles of Pack Diffusion Coating Aluminizing. Pack diffusion coating may be considered as a CVD process carried out with the aid of a powder mixture pack , in or near which the part to be coated substrate is immersed or suspended, containing the element or elements to be deposited source , a halide salt activator , and an inert diluent such as alumina filler . When the mixture is heated, the activator reacts to produce an atmosphere of...
Testing and Control of Cleaners
Alkaline cleaners lose strength through use and dilution, as well as through the necessity of replacing lost cleaning solution with water, so a reliable method of determining cleaner concentration is necessary. The most commonly used method is acid-base titration. In this procedure, an accurately measured amount of alkaline cleaner is placed in a container, and then an acid of specific concentration is slowly added titrated to the solution with stirring until a specific pH is achieved. The...
Electrochemical Machining
ECM consists basically of the electrochemical dissolution of the surface metal of a workpiece by conversion of metal to its ions by means of an electric current. The whole process is accomplished in an electrolytic cell by applying a positive anodic potential to the workpiece and a negative cathodic potential to the tool used to shape the workpiece. ECM can be used for shaping, finishing for improving the quality of the surface, deburring, and radiusing. One kind of ECM is electropolishing....
Reference cited in this section Ysr
8. D.B. Freeman, Phosphating and Metal Treatment, Industrial Press, Inc., 1986, p 199-217 Product Standards for Phosphating Ref 9 In most industrialized countries, there exist published standards and specifications relating to phosphating. These standards describe various processes used in the phosphating process standards of iron and steel, zinc and its alloys including both electrolytic and hot-dipped zinc as well as cadmium and, to some extent, aluminum. Some of these standards relate...
Introduction Ulb
THE TERM THIN FILMS is usually applied to metallic and nonmetallic layers of thickness of the order of microns or fractions of microns that are deposited on a variety of substrates. Their mechanical resistance is of particular interest, because high stresses often develop in the films during deposition or in service as a result of differences between the thermal expansion coefficients of the films and their substrates. This is a matter of special concern in the manufacture of microelectronic...
Engineering and Electroforming Processes 1
Electrodeposited nickel coatings are applied in engineering applications to modify or improve surface properties, such as corrosion resistance, hardness, wear, and magnetic properties. Although the appearance of the coating is important and the plated surface should be defect-free, the lustrous, mirror-like deposits described in previous sections are not usually required. Nickel electroforming is the specialized use of the nickel plating process to produce or reproduce articles by...
Pickling Defects
Pickling is frequently blamed for certain defects that appear during the pickling operation, but actually originate elsewhere. Some defects are the result of earlier operations, such as rolling, heat treating, or forging. Scratches introduced during hot rolling or pickling, as well as pickle its, both result in line-type surface imperfections that persist through subsequent processing stages. The effect of such defects on the surface properties of steel has been extensively studied Ref 25, 26 ....
General Batch Galvanizing Procedures
Wet and Dry Galvanizing. Two types of conventional batch galvanizing practices currently in use are the wet process and the dry process. Dry galvanizing was developed and refined in Europe. Recent surveys indicate that 40 of galvanizing operations in North America are wet and the remaining 60 dry. The dry process is generally considered to be less energy intensive than the wet process, but it is more sensitive to surface preparation deficiencies. Wet galvanizing involves a kettle-top flux...
Hot Dip Lead Alloy Terne Coatings
Long terne steel sheet is carbon steel sheet that has been coated by bath or continuous hot dip processes with terne metal lead with 3 to 15 Sn . This coated sheet is duller in appearance than conventional tin-coated sheet this accounts for the name terne, which means dull or tarnished in French. The smooth, dull coating gives the sheet corrosion resistance, formability, excellent solderability, and paintability. The term long terne is used to describe terne-coated sheet, whereas short terne is...
Electroless Nickel Composite Coatings
Composites are one of the most recently developed types of electroless nickel coatings. These cermet deposits consist of small particles of intermetallic compounds, fluorocarbons, or diamonds dispersed in an electroless nickel-phosphorus matrix. These coatings have a high apparent hardness and superior wear and abrasion resistance. Chemistry. Most composite coatings are applied from proprietary baths. Typically, they consist of 20 to 30 vol of particles entrapped in an electroless nickel...
ChromiumIron ChromiumNickel and ChromiumIronNickel Alloys 1
Chromium-Iron Alloys. In contrast to nickel-iron alloys, which have been investigated to replace materials based on iron-nickel alloys in magnetic applications, relatively little work has been done on the chromium-iron analog. No well-defined, large-volume manufacturing application exists for the latter. Chromium-iron alloys have been deposited from sulfate solutions. Early work in India favored a mixed sulfate-citrate solution Ref 12 , but more recent work used sulfates Ref 13 . Deposits were...
Material Properties and Their Relationship to Grindability
This section addresses the relative response of work materials such as metals, ceramics, and composites to grinding. Relative Grindability of Metals. Table 1 gives the relative grindability of seven metallic alloys. As used in the table, grindability is a calculated value that represents the efficiency of the grinding process. Grindability can be calculated using the the following relationships . Vol Lime of mater ialremoved mm3 Volume of wheel used mm1 Grindability is then a measure of the...
Chemical Control of Phosphating Processes
An efficiently operated phosphating line includes close chemical control of all materials used. Even the mineral content of plain water rinses may need to be controlled to avoid leaving a residue on parts. To obtain satisfactory phosphate coatings on steel surfaces, phosphating solutions must be chemically controlled within limits. These limits vary, depending on the specific phosphating concentrate used. Solutions should be tested on a regular schedule. Frequency of tests is determined by the...
Diffusion Coatings for Gas Turbine Engine Hot Section Parts
G. William Goward, Consultant Leslie L. Seigle, State University of New York at Stony Brook Blades and vanes made from nickel- and cobalt-base superalloys that are used in the hot sections of all gas turbine engines are coated to enhance resistance to hot corrosion. The most widely used coatings are those based on the intermetallic compounds NiAl and CoAl, which are formed by the diffusion interaction of aluminum with surfaces of the nickel and cobalt alloys, respectively. Diffusion chromium...
Preparation of Enamel Frits
Frits for porcelain enameling are typically formulated and smelted by commercial frit manufacturers to meet the end use application requirements of their enamel shop customers. Enamel shops using the wet application process normally receive their frit from their frit manufacturer in 100 lb bags. At the enamel plant, the frit is ground in a ball mill to prepare it for application to fabricated parts. The milling operations are described under the section Grinding and Blending, which follows....
Solution Control 1
Chromium-plating solutions of all three types must be subjected to periodic chemical analyses for control of solution composition. With the exception of catalyst analysis, the species and methods are identical for all chemistries. Solution control can be simplified if a record is kept of the way a particular chromium solution changes in composition during its use. Change in chemical composition depends on the number of ampere-hours of current passed through the solution, the dragout of...
Tumble Coating
Tumble or barrel coating is one of the most economical means of coating large numbers of small pieces. It is particularly useful for such articles as nails, screws, buttons, and other metal objects weighing less than 0.5 kg 1 lb . Tumble coating is also a good method for pretreating objects to be coated by other systems. In barrel coating, a predetermined weight of coating, adequate to produce a uniform finish over each item without causing drops to form, is poured over the items. The barrel is...
Example 2
The gear illustrated as Part 7 in Fig. 1 is made of 8620 steel, carburized, and hardened to about 56 to 58 HRC. Although the part is processed in a controlled atmosphere, a descaling operation is required. Abrasive blasting with fine steel grit or chilled iron shot SAE G40 or S170 proved the most economical method for cleaning large tonnages of such parts used in the manufacture of trucks, tractors, and similar vehicles. Acid pickling was precluded because of hydrogen embrittlement, and...
TiCl4 CH4 TiC 4HCl
The reaction temperature ranges from 850 to 1050 C 1560 to 1920 F , and pressure varies from less than 0.13 to 101 kPa 1 to 760 torr in a hydrogen atmosphere. Other carbon sources are toluene CH3C6H5 and propane C3H8 . Boron nitride Ref 34 is produced in a hydrogen atmosphere by the reaction of boron trichloride and ammonia At a deposition temperature of 1300 C 2370 F , a low-density 1.5 g cm3 boron nitride is obtained. Density increases with increasing temperature and reaches 2.0 g cm3 at 1600...
Table 7 Effect of boron content and complexing agent on internal stress in
Based on tests with 12 m thick coatings on a Brenner-Senderoff Spiral Contractometer. Stresses are tensile. Physical and mechanical properties of borohydride-reduced electroless nickel are summarized in Table 6 Ref 2, 6, 34 . For comparison, the properties of a hypophosphite-reduced coating containing 10-2 p are also listed Ref 12 . The density of electroless nickel-boron is very similar to that of nickel-phosphorus coatings of equal alloy content. The density of borohydride-reduced coatings...
Peening Test Strips Holder and Gage
SAE standard J442 describes the test strips, strip holder, and gage used in measuring shot peening intensity. If a thin flat piece of steel is clamped to a solid block and exposed to a blast of shot, it will be curved after removal from the block. The curvature is convex on the peened side. The extent of this curvature on a standard sample serves as a means of measurement of the intensity of the peening. Standard test strips of three thicknesses used are shown in Fig. 14. Made of 1070...
Nickel Plating
Electrodeposits of nickel exhibit a wide variety of properties, depending on composition of the plating bath and operating conditions. They may be classified according to application or appearance as general-purpose, black, and bright. More detailed information on plating bath chemistries and processing parameters can be found in the article Nickel Platingin this Volume. Plating Baths. General-purpose nickel deposits, produced by Watts, sulfamate and fluoborate baths, are essentially...
Pack Cementation Aluminizing of Steels
L. Keith Bennett and George T. Bayer, Alon Processing, Inc. The pack cementation aluminizing process is used to improve the performance of steels in high-temperature corrosive environments. The complex aluminide intermetallic coatings formed during the process exhibit superior resistance to oxidation, carburization, and sulfidation Ref 57 . Table 3 provides a partial listing of commercial applications for the pack aluminizing process. Typical applications include carbon steel heat exchanger...
The Watts Solution and Deposit Properties
The nickel plating solution described by Watts in 1916 was a major milestone in the development of nickel plating technology. The solution eventually replaced all others in use up to that time. It remains the basis of most decorative nickel plating processes, and it is used for engineering applications and for electroforming. It is operated at elevated temperatures and is capable of being used with high current densities. The composition of the modern Watts bath is included in Table 2. The...
Surface Hardening of Pearlitic Malleable Iron
Fully pearlitic malleable iron may be surface hardened by either induction heating and quenching or flame heating and quenching. Laser and electron beam techniques also have been used for hardening selected areas on the surface of pearlitic and ferritic malleable iron castings that are free from decarburization. Generally, hardness in the range from 55 to 60 HRC is attainable, with the depth of penetration being controlled by the rate of heating and by the temperature developed at the surface...
References cited in this section Xfy
1. H.Y. Chen, J. Electrochem. Soc, Vol 118, 1971, p 551 2. R.J. Tedeschi, Met. Finish., Nov 1971, p 49 Process Control Microprocessor-controlled modulation of applied direct current to improve the electrodeposition process has found use in reel-to-reel selective plating, automatic tab plating, barrel line plating, still plating, electroforming, anodizing, electrocleaning, electropolishing, and electromachining. It recently has been adapted for use with semiconductor bump and wafer plating...
Curing of Paint Films
Curing is the process of converting an applied coating to a dry film. Baking or thermosetting coatings require heat to cure. Those coatings that dry by evaporating the solvent are air drying or thermoplastic. Ovens are used to supply the energy needed to cure the film and or evaporate the solvent. Heat is transferred by conduction, convection, or radiation. Convection and radiation are used in ovens for baking paint. Conduction takes place in shielded areas only incidentally. Convection baking...
Example 2 Automated Immersion Coating of Cast Iron Cylinder Heads in a Zinc
The equipment requirements for zinc phosphate coating of cast iron cylinder heads include the use of an automatic indexing immersion phosphating machine. These parts, which weigh 121 kg 267 lb each, are processed in baskets, three to a basket, and are loaded standing on their sides to facilitate drainage of solutions from inner passages. A coating weight of 3.8 g m2 1.2 x 10-2 oz ft2 is obtained. The machine includes a phosphating tank that accommodates three workbaskets, thus allowing...
Effect of Galvanizing Process on Substrate Materials
Tensile Strength, Impact Toughness, and Formability. The tensile strength, yield strength, elongation at rupture, and reduction of area of hot rolled steels remain virtually unchanged after hot dip galvanizing. A study by BNF Technologies, Oxfordshire, England, indicates that, in welded structures, the weld stresses may be reduced by 50 to 60 as a result of hot dip galvanizing. Increased strength levels induced by cold working or heat treatment are generally reduced by hot dip galvanizing. The...
Coatings for Thermoplastic Olefins
The use of thermoplastic polyolefin TPO for exterior automotive parts has grown dramatically in recent years due to its low cost, low density, wide range of moduli, excellent appearance, and recyclability. However, due to its low surface energy, a pretreatment is required for good paint adhesion. Most TPOs have a total surface tension of about 30 dynes cm, with a polar contribution of less than 3 dynes cm. Although plasma or flame treatment of TPO can increase surface tension Ref 35 and result...
Electroless Nickel Plating
Electroless nickel plating is used to deposit nickel without the use of an electric current. The coating is deposited by an autocatalytic chemical reduction of nickel ions by hydrophosphite, aminoborane, or borohydride compounds. Details of the process can be found in the article Electroless Nickel Plating in this Volume. When sodium hypophosphite is the reducing agent, the deposit generally contains between 3 and 11 P. The boron contents of electroless nickel range from 0.2 to 4 wt and from 4...
Vapor Degreasing
Vapor degreasing is a generic term applied to a cleaning process that uses the hot vapors of a chlorinated or fluorinated solvent to remove soils, particularly oils, greases, and waxes. A vapor degreasing unit consists of an open steel tank with a heated solvent reservoir, or sump, at the bottom and a cooling zone near the top. Sufficient heat is introduced into the sump to boil the solvent and generate hot solvent vapor. Because the hot vapor is heavier than air, it displaces the air and fills...
Effect of Process Variables on Scale Removal in Sulfuric Acid
The composition of scale on hot-rolled strip is primarily influenced by the cooling rate after coiling. When pickling with sulfuric acid, this is important because conditions that increase the amount of FeO in the scale rapid cooling render it more easily pickled Ref 20, 21 . With hydrochloric acid, the solubility of Fe3O4 is significantly greater than it is in sulfuric acid Ref 22 . Therefore, the relative amounts of FeO versus Fe3O4 in the scale layer are of less importance with hydrochloric...
Batch Pickling
Carbon steel rod, wire, and pipe are usually batch pickled in sulfuric acid solutions. Rod ranging from 5 mm 0.200 in. to over 17 mm 0.675 in. in diameter in coils weighing from 136 kg 300 lb to more than 454 kg 1000 lb can be pickled using one to ten coils at a time. With wire, especially for diameters below 3 mm 0.100 in. the packing effect makes it difficult for the acid solution to penetrate and contact all wraps uniformly. To promote better cleaning of wire, the coil sizes can be...
Special Procedures for the Removal of Grinding Honing and Lapping Compounds
Residues remaining on parts after honing or grinding are usually mixtures of metallic and abrasive particles with oil-based or water-based cutting fluids. Thus, the methods recommended earlier in this article for the removal of chips and cutting fluids are applicable also for the removal of grinding residues in a majority of instances. Lapped parts are usually more difficult to clean than honed or ground parts. Lapping residues are composed of extremely fine particles of various abrasives,...
Pickling Solutions
For carbon steel, sulfuric acid H2SO4 is used in most batch pickling operations, whereas hydrochloric acid has become the pickling agent of choice, as of 1994, for continuous operations with wire and strip. Hydrochloric acid HCl is also used for special purposes, such as etching before galvanizing or tinning. Nitric-hydrofluoric acid mixtures are used to pickle stainless steel. Hydrofluoric acid is sometimes used when pickling castings to remove sand. Mixtures of hydrochloric and sulfuric acids...
Disposal of Spent Pickle Liquor
Spent pickle liquor SPL from sulfuric acid pickling may contain from 2 to 15 wt H2SO4 and 5 to 20 wt FeSO4. Neutralization with a lime slurry produces a mixture of sparingly soluble gypsum CaSO4 and iron hydroxide that can be pumped to lagoons for settling and, eventually, disposed of as landfill. In a modification of this process, aeration is used to convert iron hydroxide to Fe3O4, forming a dense sludge and avoiding slimes or colloids that are difficult to handle. Hydrochloric acid SPL from...
Cold Cleaning
Cold cleaning is a process for removing oil, grease, loose metal chips, and other contaminants from the surfaces of metal parts. Common organic solvents such as petroleum distillate fractions, chlorinated hydrocarbons, chlorofluorocarbons, hydrofluorocarbons, or blends of these classes of solvents are used. Cleaning is usually performed at, or slightly above, room temperature. Parts are cleaned by being immersed and soaked in the solvent, with or without agitation. Parts that are too large to...
Reviewers
James S. Abbott Nimet Industries Inc. David Anderson Aviall Inc. Max Bailey Illini Environmental John Daniel Ballbach Perkins Coie Sanjay Banerjee University of Texas at Austin Romualdas Barauskas Lea Ronal Inc. Michael J. Barber Allison Engine Company Gerald Barney Barney Consulting Service Inc. Edmund F. Baroch Consultant Edwin Bastenbeck Enthone-OMI Inc. John F. Bates Westinghouse-Western Zirconium Brent F. Beacher GE Aircraft Engines Dave Beehler New York Plating Technologies Larry Bentsen...
Surface Preparation for Electroplating
Preparation for plating is one of the most critical of all cleaning operations, because maximum adhesion of the plated coating to the substrate is the major requirement for quality work. Maximum adhesion depends on both the elimination of surface contaminants in order to induce a metallurgical bond whenever possible and the generation of a completely active surface to initiate plating on all areas. In addition to pickling or other descaling operations, adequate cleaning requires multistage...
Example 1
Barrel or vibratory tumbling is probably the most economical method for removing scale or rust from steel parts like Part 10 in Fig. 1, if they are no larger than about 50 to 75 mm 2 to 3 in. . For similar but larger parts, abrasive blasting is usually a better choice. However, if such parts are close to finished dimensions and these dimensions are critical, a nonabrasive method of cleaning should be chosen. If parts are made of low-carbon steel and are not heat treated, pickling in inhibited...