Cascade e-Ion Plasma™ Surface Hardening & Texture Control
Role of the Cascade e-Ion Plasma Plume
The Cascade e-ion Plasma is a versatile machine that may be used to impact the surface texture and roughness for metals (Cascade e-Ion source), ceramics (Cascade e-Ion EIZ) or soft plastics (e-Ion LIP). With the e-Ion Plasma machine one may rapidly "deburr" or create new surfaces, depending on the ions used and other properly set conditions that change for specific alloy surfaces and temperature. Contact the manufacturer, MHI. Nano scale features of texture and porosity that are now known to be important for surface bioactivity or roughness can nowbe engineered. Sometimes trial and error experimentation may be involved regardless of whether a titanium, steel, cobalt or PEEK alloy.
In its several modes the e-Ion Plasma™ can deburr, ionic co-deposit to alter surface porosity and be used simultaneously for thermal action in various combinations of use modes to obtain the best surface. Numerous studies are underway for smoothening glasses, semiconductors and high hardness materials such as carbides, nitrides and borides. Selective smoothening or roghening studies with composites and muticompositional alloys are underway also. The initial surface conditioning plays an important and non-intuitive part in the surface action.
Every competitive "deburring" process has advantages and disadvantages. When comparing processes for a particular action, the comparison should include speed, reliability, tolerance, energy efficiency, chemicals and other environmental foot-print features including noise for comparison making. Mechanical processing (such as drilling, grinding, stone-tumbling and polishing) may change or damage materials on account of focused stresses which then may lead to residual cracks, residual tensile stresses and/or changes in the microstructure; thus reducing the service life of the part. Electro--polishing may require chemicals that need to be stored, replenished and disposed. The e-ion on the other hand uses only air (or other gas of choice) and electricity as input to the machine. High kinetic and thermal energy ions are used for deburring in the e-Ion Plasma process. It is a noiseless yet controllable process and because of the small foot print of the cascade e-ion device, may be used on a table-top for almost all configurations. The Cascade e-Ion Plasma™ i.e. the CleanElectricFlame® can be used in a continuous manner with a belt or robot part-handler. MHI provides all the high temperature holding accessories required by the user for addition to a standard part manipulators. See also welding page.
Additional Benefits with the Cascade e-Ion
Although not all the benefits of a new technology like the e-Ion Plasma can be known at this point, several benefits may be anticipated. For example, with the e-Ion Plasma, the rapid "deburring" step can be thought to be combined with a rapid surface niriding and bulk sintering step. The ions do not require line-of-sight beam and the product does not have to be electrically grounded. This type of sintering is called 4DSintering® which is a Trademark of MHI Inc. Simultaneous ion peening operations can be envisaged. Similarly welding and weld smoothing may be anticipated as simultaneous operation. The scale from welding and the chromium depleted layer underneath the weld roughness must be normally removed for example for improved stainless steel, sea-side corrosion resistance. Mechanical polishing to match the finish on the parent material is often used but this must be done carefully so that cracks are not introduced which can lead to stress-corrosion cracking. More Online Information.
Sometimes surface roughness is further reduced by deposition. The e-Ion depositor attachment may be used with the same machine.
Example: Starting from surface with a Ra = 20-40um, for an unsintered powder metallurgy produced alloy part for an alloy that sinters around 1700K, a Ra = 4um surface is easily obtained in minutes to an hour of non-line-of-sight surface e-Ion "deburring" operation. Multiple parts can be made simultaneously. The production cost saving per part when comparing labor time for 1 hour vs. 3 days is substantial. The savings from lessened environment degradation is substantial. The energy savings per year could be thousands of dollars in benefit. Please contact MHI for more precise calculations and to work with you to ensure best amortization cost for your specific location. Please Contact Us for more information for the best surface-finish for metals, ceramics, glass, oxides, garnets, silicon carbide and many other materials that require nanoscale or microscale smoothening or manipulation.
Grit to Microns
A high energy and high velocity e-Ion Plasma™ CleanElectricFlame™ is shown below which can be used for in-situ surface operations within seconds or minutes for the completed biomedical part (entire surface), casting, forging or powder-metallurgy fabricated parts. Curved and non-line-of-sight regions can be treated.
Scale of Roughness Texture
(Related to the resolving power required of the measurement probe, with light ~ 0.5 micron, with electrons and AFM, theoretically it is ~ 0.1 nanometer (nm))
Deepest ocean trench: 10.994 Km
Highest mountain: 8.850 Km
Human scale: ~1 m
Human organ scale: ~10 cm
Spoons and forks that fit a human mouth: ~1 cm
Pencil tip: ~1 mm
Grain of salt: ~0.1-1 mm
Human hair or dust mites: ~0.1 mm
Bacterium: ~1-10 micrometer (the typical size of the autocorrelation length features on a smooth surface)
Phages (bacterial virus): ~0.1 micrometer (this the industrial level of polish in the 21st Century)
Large molecules or virus: ~10-100 nm
Atoms: ~0.1-1 nm (most commonly used materials are comprised of atoms with diameters in the 0.1 nm range)
Water molecule: 0.275 nm
Nucleons: ~10^-6 nm
Electrons: ~10^-7 nm
Planck's length: ~10^-26 nm (smallest scale believed to exist in space-time)
Other texture properties: The ACF, the auto-correlation function is a measure of how similar the texture is at a given distance from the original location. If the ACF rapidly becomes zero along a given direction, the surface becomes“uncorrelated” with the starting measurement location. The Sal (also called ACL or ß), is the Auto-correlationlength, a measure of the distance over the surface such that the new location will have a minimal correlation with the original location. For anisotropic surface texture, the direction along the surface for the ACL is the one which has the lowest ACL value. The STR which ranges from 0-1, for anisotropic to isotropic ia a measure of the spatial isotropy. Spacial isotropy STR~1 is good feature to have except in certain directional tools. The word “lay” is also used in the metal machining literature to indicate surface anisotropy but this best to have at a repeatable heirarchical scale acrooss many lenght scales. Contact MHI for more information on Shannon and other proofs and how we can recommend technology companies that can do measurements for you.
The value of hardness depends on the material and processing conditions. The measurement of hardness also depends on the strain rate sensitivity on the harness and thus the measurementof Hardness is not always representative of a hardness during use in dynamic consitions. Please contact MHI for high hardness, low distortion and tunable coefficient of friction surfaces with the highest Str.
What is the Magnitude of Possible Energy Savings: An astounding ~23% of the world’s total-energy consumption (greater than 575 ExaJ/Y) (Exa = 10^18), originates from tribological contacts. About 20% of this total energy (~114 EJ/Y) is used to overcome friction and ~3% (~17EJ/Y) is used to remanufacture worn parts and spare equipment (Friction 5(3): 263–284, ISSN 2223-7690, 2017). Most friction pairs that are in use are estimated to be from contacts that are about 50% metallic (bearings and bushings and rotary components). New technolgies are reducing dry friction considerably (Tunable coefficient of friction with surface texturing in materials engineering and biological systems Current Opinion in Chemical Engineering, vol.19, p. 94-106, 2018)
Stainless Steel, High density plastics, dental alloys, gold alloys, superalloys, Nitinol oxide conditioning, Ni-Ti, Ti-Al, Ni-Al, castings, forgings and many others where roughness needs to be reduced or surfaces have to be peened.