ION IMPLANTATION PROCESS
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| Overview: |
Ion implantation is a potential enhancement method for chrome plating or other plating processes, as well as a process that can improve engineering properties of substrate materials. Therefore, any site using electrolytic hard chrome plating or other plating processes could be a candidate for implementation, as could original equipment manufacturers to improve the service life of components such that refurbishment would not be necessary until a much longer service period has passed.
Ion implantation is a surface modification process in which ions are injected into the near-surface region of a substrate. High-energy ions, typically 10–200 kiloelectron volts (KeV) in energy, are produced in an accelerator and directed as a beam onto the surface of the substrate. The ions impinge on the substrate with kinetic energies 4–5 orders of magnitude greater than the binding energy of the solid substrate and form an alloy with the surface upon impact. Virtually any element can be injected into the near-surface region of any solid substrate. Commonly implanted substrates include metals, ceramics, and polymers. The most commonly implanted metals include steels, titanium alloys, and some refractory metals. During the conventional Ion Implantation Process, a beam of positively charged ions of the desired element (either a gas such as nitrogen or a metal such as boron) is formed. Beam formation of a gas (e.g., nitrogen, oxygen, carbon, and inert gases) occurs by feeding a gas into an ion source. In the ion source, electrons, emitted from a hot filament, ionize the gas to form plasma. Ionization of the element is performed for the purpose of acceleration. Incorporation of an electrostatic field results in the acceleration of the positive ions at high energies under high vacuum (pressures below 10 -5 Torr). The ions penetrate the component surface, typically to a depth not exceeding 0.1 µm. The near-surface alloy produced by implantation is different from conventional coatings in that the implanted ion is surrounded by atoms of the original surface material. Alloying at the surface can be as high as 50 atomic percent of the implanted element. It produces no discrete coating, nor will delamination of the altered surface occur. Forming a beam of a solid element (e.g. metals, metalloids, and certain non-metals) can occur by one of four methods. The first method is commonly used in the semiconductor industry, which requires extremely high-purity beams. In this method, a reactive gas, such as chlorine, is used to form the plasma. A metal chloride is generated as the chlorine ions chemically react with the metal walls of the ion source. The metal chloride then is ionized to form plasma of metal and chlorine ions. An analyzing magnet is used to separate the chlorine ions from the desired metal ion beam. The second method employs sputtering to generate metal ions. In this method, inert argon gas is ionized. The positively charged ions are attracted to a negatively biased metal target. As the argon ions strike the target, pure metal atoms and ions are dislodged from the target. The metal ions are extracted, focused into a beam, and directed toward the part to be implanted. The two other methods of forming a beam of a solid are similar to that of the sputtering method. Variations of the sputtering method use thermal or electron beam evaporation, or cathodic arc (initiating an arc on the surface of a metal target to evaporate the metal) to generate the metal vapors. These methods of generating beams of solids do not require the costly analyzing magnets and provide very high ion currents. A newer form of ion implantation involves using a plasma within the chamber from which gaseous ions are extracted. Similar to the beamline method, the gas is excited to form a plasma, typically through the use of an RF antenna. The positively charged gas ions are accelerated towards the substrate by subjecting the substrate to high voltage pulsed biasing. This method of implanatation is referred to as plasma source ion implantation (PSII) and circumvents some of the line-of-sight issues associated with conventional beamline methods. Possible products of an ion implantation process are the formation of nitrides, borides or carbides, or the occurrence of localized alloying. With this process, properties such as hardness, wear resistance, corrosion resistance, and fatigue may be altered according to the selected implantation element. Ion implantation can provide 2–100-fold improvements in wear life, depending on the type of wear and service environment. |
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| Compliance Benefit: |
Ion implantation, by reducing the use of hazardous plating materials such as hexavalent chromium, will assist facilities
in meeting environmental and health compliance standards. For instance, the reduction of hazardous waste helps facilities
meet the requirements of waste reduction under RCRA, 40 CFR 262. It may also help facilities reduce their generator status
and lessen the amount of regulations (i.e., recordkeeping, reporting, inspections, transportation, accumulation time,
emergency prevention and preparedness, and emergency response) they are required to comply with under RCRA, 40 CFR 262.
In addition, since hazardous plate materials are reduced, a facility is less likely to meet any of the reporting thresholds
for hazardous substances/chemicals under SARA Title III (40 CFR 300, 355, 370, and 372; and Executive Order 13101).
As an added benefit, ion implantation should result in improvements in a product’s service life. By extending the life of the substrate, overall repairs to the substrate should be reduced. Repair work often employs hazardous chemicals (including the reduced use of stripping agents, cleaners, etc.). The compliance benefits listed here are only meant to be used as general guidelines and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g., the amount of workload involved. |
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| Materials Compatibility: |
No materials compatibility issues were identified. However, substrates can be overheated if not properly heat sunk (thermal dissipation), which can anneal a tempered substrate. This situation will adversely affect the overall engineering properties and can cause dimensional distortion. Therefore, components must be thoroughly reviewed prior to treatment.
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| Safety and Health: |
Caution must be exercised with the equipment. Proper personal protective equipment must be worn and other safety practices must be employed. Specific areas of concern are as follows:
Consult your local industrial health specialist, your local health and safety personnel, and the appropriate MSDS prior to using the technology. |
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| Benefits: |
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| Disadvantages: |
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| Economic Analysis: |
The National Defense Center for Environmental Excellence (NDCEE), operated by Concurrent Technologies Corporation,
was tasked to test several alternatives, including ion implantation, to current plating processes.
The NDCEE also conducted an environmental cost-benefit analysis (ECAMsm) in which the Electroplated Hard Chromium
(EHC) plating process at Anniston Army Depot, Alabama, was compared to EHC with supplemental ion implantation via
beamline ion implantation for intermediate bearing housings.
EHC represents a significant contribution to hazardous, carcinogenic waste generation and pollution control costs. Increasingly stringent Occupational Safety and Health Administration and Environmental Protection Agency regulations will continue to increase costs of hexavalent chromium processes. Assumptions:
Operational Costs: The costs that were determined from the process data for EHC are $2.76 per square centimeter and $1.18 per square centimeter for PSII in addition to the EHC costs and $6.96 per square centimeter. Economic Analysis Summary: In general, the processing costs of PSII and beamline ion implantation are an additional cost to EHC costs, but ion implantation provides an extended life to each component due to improving engineering properties. Therefore, this extended wear life makes it economically feasible to implement ion implantation as noted below in the payback periods for each process. Also, the reduction in repairs reduces the exposure to EHC. As shown in Table 1, ECAM results revealed that the proposed supplemental treatment of hard chromium plating with PSII has the potential to reduce annual operating costs associated plating activities, as compared to their current hard chromium electroplating process. Table 1. Financial Implications of Installing and Operating IBAD Equipment to Supplement the Current Hard Chromium Electroplating Process with PSII
a - This value was calculated by extending the annual operating costs over the anticipated extended life of the component.
The actual economic impact related to installing the IBAD equipment is site specific and will vary depending on the number of actual operating hours, future workloads, and process performance. It must be remembered that the above values only apply to the hard chromium electroplating and PSII. Variations in any of the unit operations or alternate options are likely to have a cost impact.
*Note: These findings reflect purely operational costs and should only be used as a guideline in understanding the cost differences in ion beam processes and EHC plating.
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| Approving Authority: |
Appropriate authority for making process changes should always be sought prior to procuring or implementing any of the technologies identified herein.
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| NSN/MSDS: |
None Identified
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| Points of Contact: | For more information
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| Vendors: | This is not meant to be a
complete list, as there may be other suppliers of this type of
equipment.
Implant Sciences Corp.
ULVAC Technologies, Inc.
DANFYSIK A/S
UNIMERCO Inc
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| Related Links: |
Case Technology's
description of ion implanting technology used in the semiconductor industry
University of Wisconsin – Madison PSII Laboratory |
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| Sources: |
Concurrent Technologies Corporation, NDCEE Annual Technologies Publication, April 2003.
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| Supplemental: |
Located in the NDCEE Demonstration Facility, this technology has both ion implantation and ion beam assisted deposition capabilities.
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