Appliance Design - November 2007 - (Page 50)

METALS & METAL PARTS Fig 4. Comparison of corrosion resistance as measured by salt spray endurance in hours in accordance with ASTM B117. Keronite on aluminum Hard chrome Hardened tool steel Hard anodized aluminum 304 Stainless Steel Mild Steel Aluminum 0 500 1000 1500 2000 2500 Hard Chrome Electroless Nickel Hard Anodizing Keronite Fig. 3. Comparative hardness of different surfaces measured in HV (Vickers). 0 500 1000 1500 2000 2500 process yields: 4A thin intermediate layer, providing the strong molecular bond with the substrate. 4A functional, hard ceramic layer that protects against wear and corrosion. On aluminium, this layer has a micro-hardness of 500-2000 HV, depending upon the alloy, and a fine scale porosity of 2 percent to 10 percent. This functional layer comprises hard, crystalline phases in a matrix of softer oxide phases. This complex structure gives Keronite its unique combination of high hardness and wear resistance. 4An outer layer with up to 20 percent porosity, but on such a fine scale that the Keronite layer can be considered relatively dense. This very finescale pore structure is ideal for the retention of lubricants such as PTFE, producing a tough, non-stick or lowfriction composite, or for impregnation with paints or lacquers. Properties of Keronite Depending upon the alloy selected and the thickness of the ceramic layer generated by the process, the hardness of Keronite surfaces ranges from 500 HV to as much as 2000 HV — making it three times harder than hard anodizing and even harder than hardened tool steel, glass or many silicon-containing compounds. Even on magnesium, the hardness can reach 600 HV. (See Fig. 3.) It is the unique structure of the Keronite ceramic layer that gives it such remarkable performance characteristics. Despite this extreme hardness, the fine scale porosity of Keronite gives it a degree of compliance which, combined with the hardness of the surface, makes for exceptional wear resistance — surfaces up to seven times more wear resistant than hard anodized equivalents on aluminum and far less prone to cracking around corners than hard anodizing. It also outperforms electroless nickel in ball-on-disk tests. On magnesium, traditionally quite a soft material, just 10 microns of Keronite will withstand 10,000 cycles of a CS17 NORTH AMERICA’S LEADING & LARGEST PERFORATOR Supplying Perforated Components to OEMs since 1915. Our emphasis on quality, on-time delivery, fair prices and the capability of producing materials in tolerances higher than industry standard has made DIAMOND North America’s leading and largest perforator. Call for our 188 page catalog covering all aspects of the perforating process, material information, company capabilities, tolerances and technical studies data. abrasion wheel without any sign of damage. Research at the University of Cambridge has demonstrated that the stiffness of Keronite can be as little as 30 GPa, making it more strain-tolerant than most ceramics. When impregnated with PTFE, the wear resistance of Keronite surfaces can be even further enhanced. Corrosion has always been the limiting factor in the use of magnesium, but Keronite on AZ91D magnesium alloy withstands 1,000 hours in salt spray (in accordance with ASTM B117) without needing to seal the surface. In one test, it even reached 2,000 hours with no detrimental effect. (See Fig. 4.) Keronite surfaces have other functional characteristics including thermo-optical and dielectric properties. As an insulator, it can act as an effective thermal barrier and has excellent thermal cycling properties. It has a low friction coefficient, and is used as a pretreatment for topcoats such as paints or for other metals or ceramics to form composite coatings. On magnesium Magnesium is currently going through a period of great change with world demand increasing rapidly, and prices falling at a similar pace as China takes on a more dominant role. World production of magnesium has increased by over 50 percent www.applianceDESIGN.com 2 4 3 W. E I G H T H S T. W YO M I N G , PA 1 8 6 4 4 800.233.9601 W W W. D I A M O N D M A N . C O M For more Information Enter 120 50 applianceDESIGN AD04071Diam.indd 1 November 2007 2/22/07 9:20:32 AM http://WWW.DIAMONDMAN.COM http://WWW.DIAMONDMAN.COM http://www.appliancedesign.com

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Appliance Design - November 2007 Contents Editorial Shipments/Forecasts News Watch Today’s LEDs are Brighter and More Colorful than Previous Versions, Allowing Designers More Opportunities to Improve and Differentiate Their Products. When Converting from CCFL to LED Backlights in LCD Panels, New Driving Methods are Needed. Electrowetting Technology Allows Displays to be Designed in an Extensive Range of Colors. Noise Problems are Not Always Easy to Find or Fix, but Acoustic Labs Can Help Designers Ferret Out the “Good” Noise from the “Bad.” A New Sanitization Protocol for Clothes Washers Combines the Best of Three Well-Established Provisions to Ensure Efficiency, Quality and Safety. Stricter EMC Requirements Raise the Bar for Appliances with Electronic Controls and Require Testing to New Levels. Despite Added Cost and Complexity, Gas-Modulating Systems have Migrated from Large-Scale Boiler Applications to Smaller Residential and Commercial Furnaces and Appliances. A New Treatment Technology Hardens the Surface of Light Alloys such as Aluminum and Magnesium and Expands Their Potential Applications. DesignMart Advertiser’s Index Association Report: AHAM

Appliance Design - November 2007

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