Surface-engineering Options

For mild steel or cast iron parts, consider  

For medium-carbon steel parts, consider the surface treatments listed above for mild steels, plus local surface hardening, for example, flame, induction, or laser for maximum loading, and for large rolling components (e.g., large cylindrical roller bearings and tracks). 

For low-alloy steel parts (steels containing chromium, vanadium, and/or molybdenum), consider the surface treatments listed above for both mild and medium-carbon steels, plus nitriding or nitrocarburizing to give a diffused case. Follow with oxidation and oiling treatment for corrosive conditions. 

High-Alloy and Tool Steel Parts. Tool steels or high-speed steels (including AISI440C, and the A, D, and M series steels) can be heat treated to high hardnesses and are wear resistant in their own right. For additional wear resistance and to reduce pickup, particularly in metalworking operations, consider  

PVD coatings, for example, TiN, CrN, and diamondlike carbon wUl give low friction and low wear under moderate loads. Used on cutting and cold-forming tools 

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Table 1 Surface engineering options and property benefits...

In choosing a SAM system for surface engineering, there are several options. Silane monolayers on hydroxylated surfaces are an option where transparent or nonconductive systems are needed. However, trichlorosilane compounds are moisture-sensitive and polymeri2e in solution. The resulting polymers contaminate the monolayer surface, which occasionally has to be cleaned mechanically. CarboxyUc acids adsorb on metal oxide, eg, AI2O2, AgO through acid—base interactions. These are not specific therefore, it would be impossible to adsorb a carboxyUc acid selectively in the presence of, for example, a terminal phosphonic acid group. In many studies SAMs of thiolates on Au(lll) are the system of choice. 

When we initiated the program for evaluating the various engineering options for surface storage, it was evident that there were several factors to be considered, each having an impact on the safety, efficiency, and acceptability of a storage concept. In general, these are ... 

ERL impact apparatus, type 12 This test was developed by the US Army Armament Research, Development and Engineering Center and is optional for use. The machine (Bruceton Machine) Type 12 consists of a striker pin (made of hardened tool steel, ground and polished) with surface in contact... 

Physically, a two-zone speckled enclosure is characterized by the fact that the view factor from any point on the enclosure surface to the sink zone is identical to that from any other point on the bounding surface. This is only possible when the two zones are intimately mixed. The seemingly simplistic concept of a speckled enclosure provides a surprisingly useful default option in engineering calculations when the actual enclosure geometries are quite complex. 

Today s new engineered composites provide designers with a wealth of options and challenges. Many structural adhesives are currently available, and the correct adhesive choice is crucial. Factors to consider include VOC content, surface preparation, working and fixture times, requirements of the application, and dynamic fatigue resistance. 

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