Cascade e-Ion Plasma™ Surface Hardening & Texture Control

Surface Roughness

Units: 1 micron (um) = 39.37 micro-inch (u-inch) = 1000 nanometer (nm).
Surface roughness is one measure of the texture of a surface. Several other steps are also necessary, such as the autocorrelation length (ACL or β), anisotropy (Str), Surface density, Skewness, Kurtosis, and volumetric measurements. Texture assessment depends on the probe’s resolving power. In an approximate sense, the human eye’s resolution is about 0.3 mm. The resolution of an optical light microscope is ~500 nanometers (nm) spatially and a micron in the height direction (confocal microscopy provides a smaller height measurement possibility). In a scanning microscope, it is about 10- 100 nm, depending on the electron wavelength. For a transmission microscope, it could be less than 1 nm. For an atomic force microscope, it could be 0.2nm.
The roughness of a surface asperity height is commonly reported as an Ra number (the arithmetic average roughness of a surface)or reported with an Rq number (root mean square RMS value of roughness).
More advanced reporting procedures include values for waviness, kurtosis, surface skewness, ACL, and Str; however, Ra and Rq adequately capture the height roughness.
Units: The engineering units for both Ra and Rq are either micro-inch or nanometers.
1 microinch= 0.0254 microns =25.4 nanometers
Peening or burring improves a metal surface’s material properties. Ion burring with e-ion Plasma is a relatively new process that can be used for curved and complex shapes.
Cast surfaces display Ra of about 50-250 u-inch. Sand castings display higher roughness, and plaster shell-type investment castings and die castings show lower roughness values. Squeeze castings also exhibit a higher average roughness.

Use no-burr technology with e-ion or GoldenBlue® tools.

Importance

Surface roughness can change the look and feel of products (gloss and luster) and their friction and wear properties. Inadequate roughness can also affect the durability, fatigue, biocompatibility, and reliability of the processed part—Cascade e-ion information request.
Several quick machining operations leave behind burrs.
Roughness impacts life by affecting wear resistance, erosion resistance, fatigue resistance, creep-fatigue interaction, and other material design parameters.
Roughness is called out for metallic, composite, and ceramic parts used in turbomachinery, combustors, engines, cylinders, and other engineering parts.
The more commonly reported measurement number for polymeric and other soft surfaces relates to specular reflectivity; the Ra and Rq are generally not called out.
High roughness can cause turbulence. A poor casting finish can dramatically reduce energy efficiency in any fluid-flow device, e.g., a pump or turbocharger. e-Ion techniques can control roughness.
For more information regarding surface roughness and surface finishing, see this site, which discusses how coatings fill the voids between sand grains and can also act as refractory, limiting the defects and loss of integrity that can occur with higher melting point alloys. Coatings make casting surfaces harder and smoother.
The Cascade e-Ion is a cost-effective method of altering the texture of a surface, thus changing several engineering properties, including friction and wettability. It prevents slip-stick and improves color and luster.

Role of the Cascade e-Ion Plasma Plume

The Cascade e-Ion Plasma is a versatile machine that enhances the surface texture and roughness of metals, ceramics, and soft plastics. It enables rapid “deburring” and surface creation by using specific ions and adjusting conditions for different materials, including titanium, steel, cobalt, and PEEK. For more details, you can contact the manufacturer, MHI.

The e-Ion Plasma™ operates in multiple modes, enabling deburring, ionic co-deposition for altering surface porosity, and thermal action in various combinations for optimal surface treatment. Studies are ongoing to improve the smoothness of glasses, semiconductors, and hard materials like carbides and nitrides, as well as composite alloy applications.

When comparing deburring processes, consider speed, reliability, precision, energy efficiency, and environmental impact. Traditional methods like drilling and polishing can damage materials due to focused stresses. In contrast, the e-Ion Plasma process uses only air and electricity, making it noiseless and efficient, with a compact design suitable for tabletop use.

The Cascade e-Ion Plasma also integrates rapid “deburring” with surface nitriding and bulk sintering, known as 4DSintering®, without requiring line-of-sight beams. It can facilitate simultaneous ion peening and weld smoothing, improving corrosion resistance while minimizing the risk of introducing cracks.

For more information on the e-Ion depositor attachment, which further reduces surface roughness, please get in touch with us.

Example: Starting from the surface with a Ra = 20- 40 µm, for an unsintered powder metallurgy-produced alloy part that sinters around 1700K, a Ra = 4 µm 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 savings per part are substantial when comparing 1 hour vs. three days of labor time. The savings from lessened environmental degradation are substantial. Energy savings per year could be thousands of dollars. Please contact MHI for more precise calculations and to work with you to ensure the best amortization cost for your specific location. Please Contact Us for more information on the best surface finish for metals, ceramics, glass, oxides, garnets, silicon carbide, and many other materials that require nanoscale or microscale smoothening or manipulation.

Mesh sizes

Conversion

Grit to Microns

100,000	1/4
60,000	1/2
14,000	1
13,000	1.5
9,000	2.5
8,000	3
2,800	7
1,800	9
1,400	14
1,200	15
1,050	18
800	25
600	30
500	35
325	45

Cascade e-Ion

Friction Free Tools

High-energy, high-velocity e-Ion Plasma™ CleanElectricFlame® can be used for deburring surface operations within seconds or minutes for biomedical parts (entire surface), casting, forging, or powder-metallurgy fabricated parts.

It can treat curved and non-line-of-sight regions.

The Scale of Roughness Texture

(Related to the resolving power required of the measurement probe, with light ~ 0.5 microns; 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 micrometers (the typical size of the autocorrelation length features on a smooth surface)

Phages (bacterial virus): ~0.1 micrometers (this is the industrial level of polish in the 21st Century)

Large molecules or viruses: ~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 autocorrelation function, measures 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 β) is the Autocorrelation length, a measure of the distance over the surface at which the new location has minimal correlation with the original location. For anisotropic surface texture, the direction along the surface with the lowest ACL value is the one that has the lowest ACL value. The STR, which ranges from 0 (anisotropic) to 1 (isotropic), measures spatial isotropy. Spatial isotropy STR~1 is an excellent feature, except in specific directional tools. The word “lay” is also used in the metal machining literature to indicate surface anisotropy, but it is best to have a repeatable hierarchical scale across many length scales. Contact MHI for more information on Shannon and other proofs and how we can recommend technology companies that can do measurements for you.

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The value of Hardness depends on the material and processing conditions. Hardness measurements also depend on the strain-rate sensitivity of hardness. Thus, hardness measurements do not always represent hardness under dynamic conditions. 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 in use are estimated to be about 50% metallic (bearings, bushings, and rotary components). New technologies 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)