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In a 2-year program sponsored by SJAC, an aqueous electroplating process using alkaline Zn-Ni with trivalent chromium post treatment is under evaluation for high strength steel for aircraft application as an alternative to cadmium. Commercial Zn-15%Ni rack/barrel plating solutions are basis for plating aircraft parts or fasteners. Brightener was reduced from the original formula to form porous plating that enables bake-out of hydrogen to avoid hydrogen embrittlement condition. Properties of the deposit, such as appearance, adhesion, un-scribed corrosion resistance, and galvanic corrosion resistance in contact with Al alloy, were evaluated. Coefficient of friction was compared with Cd plating by torque-tension measurements. Evaluation of the plating for scribed corrosion resistance, primer adhesion, etc. will continue in FY2007.

Co+Cr2O3 is a composite coating of a cobalt matrix with 30 percent by volume embedded Cr2O3. The coating can be applied by plating using a suspension of Cr2O3 in a cobalt electrolyte. The mechanical properties of this coating are discussed. The main attribute is the excellent wear resistance of the coating especially in the temperature range of 300 to 700°C. Adhesive wear of unplated counterparts is reduced by the same amount. In contrast to nickel the fatigue strength of Co+Cr2O3 coated Waspaloy was shown to be not influenced, when heat treated at 400°C for 16 hours. Plated engine parts demonstrate the usefulness of the Co+Cr2O3 composite coatings for wear protection.

The buzz words of the 70s - Energy Shortage - have been replaced by the buzz words of the 80s - Rate Shock. As new electric generating plants come on line, the aircraft plating industry, along with the rest of the public, is seeing huge increases in their electrical energy costs. While many of these costs, such as electrical energy for rectifiers, are fixed by the process, other large costs, such as power ventilation requirements to comply with the Occupational Safety and Health Administration (OSHA) Regulations, are not unalterable. Designing an economical ventilation system does not mean compromising the worker’s safety nor violating OSHA requirements. Rather, OSHA guidelines specifically outline methods of reducing the ventilation requirements. This paper investigates several of these alternatives, including adequate hood design, push-pull ventilation systems, covering the process solution and operational methods that can greatly reduce the ventilation requirements.

With the ever increasing competition among companies to reduce manufacturing costs without sacrificing product reliability, Bendix-Pacific has engaged the use of Value Engineering in establishing contamination control on manufactured components. The process of establishing contamination control begins before the contract has been awarded. The program proceeds along the following lines: First, a foundation of sound comprehensive methods and procedures fully documented internally. Second, the application of Value Engineering to the Customer design and performance specifications. Third, the alternate proposal showing the logic and reasoning supporting the proposal. Fourth, the implementation of the proposal to the contract. And fifth, the documentation of records for the program. The important factor to remember is that, “contamination control is mandatory for system reliability, however, unrealistic levels of contamination control can only result in a gold plated product.”

To improve the fatigue properties of additive manufactured (AM) titanium alloy Ti6Al4V, cavitation abrasive surface finishing (CASF) was proposed. With CASF, a high-speed water jet with cavitation, i.e. a cavitating jet, was injected into a water-filled chamber, to which abrasives were added. Abrasives accelerated by the jet created a smooth surface by removing un-melted particles on the surface. Simultaneously, cavitation impacts induced by the jet introduced compressive residual stress and work hardening into the surface, similar to cavitation peening. In this study, to demonstrate the improvement of the fatigue properties of AM Ti6Al4V owing to CASF, Ti6Al4V specimens manufactured through direct metal laser sintering (DMLS) and electron beam melting (EBM) were treated using CASF and cavitation peening, and tested using a plane bending fatigue test.

Current NASA space suits use porous metal plate sublimators to reject the metabolic heat generated by the astronaut into space vacuum during EVA. Relying on tubular membranes instead of the flat plate of the sublimator, a proposed alternate unit has the potential to be smaller and lighter. This work outlines the operation of the proposed tubular membrane evaporator and the evaluation of possible membrane materials for the unit.

LASC-GEORGIA operates a large aircraft assembly plant located in Marietta, Georgia. This facility is owned by the U. S. Government and is known as Air Force Plant No. 6. As a part of the assembly operation, various metallic structures have metal finishes applied to them. Some of these parts are plated. A large portion of the parts are aluminum and may receive anodize or conversion coating finishes. Both the plating and aluminum finishing operations generate waste water that must be treated to meet National Pollution Discharge Elimination System (NPDES) discharge limits.

Integral black anodizing and gold plating on Mg-Li alloys were developed for spacecraft thermal control applications. The influence of various process conditions have been investigated to optimise the process. The deposits were characterized by morphological studies, adhesion test, thickness measurement, microhardness evaluation and porosity inspection. The space worthiness of the coatings has been evaluated by humidity, thermal cycling, and thermovacuum tests and measurement of optical properties. The high solar absorptance and infrared emittance (αs = 0.95, εIR = 0.93) value of black anodic film showed that these can be effectively utilized to improve heat radiation characteristics. The gold coating on the other hand provides the infrared emittance as low as 0.03, is extremely suitable in minimising the radiative coupling with other components within the spacecraft.

Many aerospace components undergo a finishing process during their manufacture. Such finishing processes include chromium, nickel, zinc and cadmium plating on steels; anodize on aluminum alloys; and various coatings on titanium and nickel base alloys. Certain of these finishing processes result in loss of fatigue strength of the part in question. Loss of fatigue strength caused by chromium and nickel plating amounting to 60% has been measured. Shot peening is frequently used on fatigue critical parts to regain fatigue properties which may have been lost due to a particular finishing operation. Shot peening is a process which bombards the surface of a part with small spherical balls. The cold working effect of the peening balls leaves the surface of the part in a state of residual compressive stress. The beneficial compressive stresses induced by shot peening are effective in increasing fatigue properties of the component.

The formation of copper-tin intermetallic compounds of the Cu6Sn5 and the Cu3Sn type at the interface between copper and solder on printed circuit (PC) boards has been previously documented, as have the circumstances under which these brittle layers can cause peeling of the solder and greatly reduce the solderability of the PC boards shown. The formation of these intermetallic layers is caused by diffusion, mainly of the copper into the solder, and is a function of time and temperature. Inhibiting the diffusion will inhibit the formation of the intermetallics. Several methods have been tried, such as the use of a metallic barrier layer. This paper will show that one of the more successful methods is the codepositing of small amounts of cobalt (0.05-0.5%) with the copper. This process is similar to the use of cobalt in wrought copper alloys to reduce solid-state mobility during thermal processes.

A new system is presented for analysis and control of the chemistry of a metal finishing line. Parameters such as metals, acids, bases and pH are measured, statistically evaluated, and replenished. Results are viewed on a CRT screen, both current and historical, and output is provided in the form of graphs, tables, printed instructions and/or relay alarms. Examples are presented of parameters measured on a metal finishing line. THE TODD AUTOMATED CHEMICAL CONTROL SYSTEM took seven years to develop1. During that time, analysis of the critical parameters of seven processes were automated. The automation began with the electroless nickel plating process and was followed by titanium chemical milling, alkaline cleaning, chromated and non-chromated aluminum deoxidizing, chromic acid anodizing, and aluminum conversion coating. Replenishment was also implemented on two of the processes.

The basic concept of brush plating has been adopted in almost every segment of industry from low tech to high tech, and from production to repair. The major drawback for the process has been the high level of operator dependency. The Single Anode Plating Machine (SAM) reduces the operator dependency and enables a computer controlled process. This article covers the details of SAM technology.

Shot peening is viewed as a process involving multiple and progressively repeated impact. The residual stress field under each impact interacts with similarly produced neighbouring fields to finally produce a residual stress distribution varying in depth but uniform in planes, parallel to the surface. Statical and dynamical aspects of single impact are considered and a number of simple theoretical expressions for the parameters of the process are presented. New concepts such as shakedown, reversed plastic yielding and Bauschinger effect as well as strain rate are thought to contribute a significant role in the process.

Electrochemical Metallizing (High Speed Selective Plating) has been widely used in aircraft maintenance, but unfortunately primarily for corrosion resistant Cadmium LHE. One reason for this myopic limitation is the fear that operating personnel, using manual techniques, could not realize consistent engineering results. A second is lack of practical shop training.

Joints represent potential weak points in the structure, the design of the overall structure tends to follow from the design of the joint. To date, metal/composite joints are general in current aircraft structure. Some of the reasons for lower joint efficiency in composites are: brittleness which means little stress relief around the highest loaded holes, anisotropy which leads to higher stress concentration factors, low transverse strength, susceptibility to delamination, and sensitivity to environmental conditions. All of these factors together with the complexity of composite failure modes make the analysis and design of composite joints far more complex than that of metallic joints. Fatigue failure is the root cause which makes aircraft unserviceable. 75-80% of fatigue failures occur in the joints of structure, therefore researching joints is very important for improving aircraft life. Much effort has been put into solving the technical challenge for composite bolted joints.

The catastrophic effect of oxidation of molybdenum on the electronic signal integrity of an airborne avionic system is documented. A chemical process for effective reduction of these corrosion products is defined, and fixtures are described for the electroplating of coaxial cables on aircraft without removal of the cables. An electrolytic process for plating nickel and gold over molybdenum is developed, and shown to have an excellent first pass through yield. The investigation and development of a repair process shows a unique approach to failure analysis and problem solving, and results in restoration of the original electronic performance of the coaxial cable.

Waspaloy sample panels are brush plated with sulfamate nickel (AeroNikl 250®) under various plating conditions. The wettability of these panels by molten brazing filler metal AMS 4777B is evaluated. Results of the observations are verified by metallographical examination. Conclusions are made about the effects of brush plating process variables on brazeability.

Multi-fastener lap joints are vulnerable to fretting fatigue when they are subjected to repeated loading. In general the fretting fatigue condition leads to degraded properties of metallic structures due to the presence of the surface stress concentration resulting at the sites of fretting pits. In many cases, fretting can result in premature structure failures therefore a series of counter measures are frequently taken to minimize fretting especially at the fastener holes. One of major factors that affect the fretting phenomena between the fastener and fastener hole is the surface condition of the fasteners. In this study, the influences of the surface texture and the surface plating of the fastener on the joint life were investigated by conducting double lap shear fatigue testing. It has been found that the joint fretting fatigue resistance is very sensitive to the surface texture of the fastener and as the surface roughness of the fastener is reduced the joint life increases.

The internal stress of electroless nickel (EN) deposits is shown to be the sum of two components, intrinsic and thermal. A method of measuring the stress components is discussed. The stress is shown to be dependent on the chemistry of the plating bath as well as the phosphorus content of the EN deposit. The corrosion behavior of EN deposits is shown to be dependent on stress and the near-surface phosphorus content. The effect of EN deposits on fatigue strength of steel is also discussed.

The new generation of high-pressure hard space suits allows designers to employ passive means of thermal control of the suit, with a reflective coating. An effort is underway to determine the coating material of choice for the AX-5 prototype hard space suit. Samples of 6061 aluminum have been coated with one of 10 selected metal coatings, and subjected to corrosion, abrasion and thermal testing. Changes in reflectance after exposure are documented. Plated gold exhibited minimal degradation of optical properties. A computer model is used in evaluating coating thermal performance in the EVA environment. The model is verified with an experiment designed to measure the heat transfer characteristics of coated space suit parts in a thermal vacuum chamber. Details of this experiment are presented here.