【正文】 , berylliumcopper, brass and stainless steel. Remended uses include cores, cavities, slides, ejector sleeves, and rotating and unscrewing cores. Its antigalling properties are advantageous on moving cores and slides. Diamondchrome also is very strippable and has no adverse effect on the base material, saving time and money when maintenance is needed. TiN is strippable as well, but it can take up to several days to remove with a peroxidebased solution. Diamondchrome can be stripped in minutes using reverse electrolysis in a caustic solution. In addition, diamondchrome can be deposited at any controlled thickness from 20 millionths of an inch to in. TiN is generally only applied in thin deposits of a few millionths of an inch. Diamondchrome can coat plex details, while TiN has very limited coverage of plex details. While TiN is very lubricious, with a coefficient of friction (COF) of (against steel), diamondchrome has a COF of —nearly three times more lubricious. NickelBoron Nitride When it es to molders’ needs for a specialty coating that offers excellent release properties and high resistance to wear, heat, and corrosion, an electroless nickelphosphorus matrix containing boron nitride particles should be considered. It has a very low COF ( against steel) and an RC hardness of 54, which can be increased to 67 RC after heat treating—a unique characteristic. Nickelboron nitride can be applied to any substrate at only 185oF and can be easily stripped without promising the base material. Though it is approximately 20 percent more expensive than nickelPTFE, this coating will outperform nickelPTFE at up to 1250oF, which far surpasses the 500oF maximum limit for all PTFEbased coatings. Because applying nickelboron nitride is an autocatalytic process, it requires no anode, therefore saving time and money. In addition, it will not promise thermal conductivity of the mold. Applications include unscrewing cores for closures, where reduced cycle times are essential. Where lubricity is needed for better release from deep ribs, zerodraft cores, textured surfaces and “sticky” polymers, a nickelPTFE posite will greatly improve part release and enhance resin flow by as much as 4 to 8 percent for shorter cycle times. COF is against steel. It should be noted that applying pure PTFE to the mold adds high lubricity, but only a very shortterm benefit. PTFE by itself has no hardness, so it won’t last. But a dispersion of 25 percent PTFE by volume in a codeposit with nickel results in 45 RC hardness for added wear and corrosion protection. Tried and True Despite the new coating science, we cannot throw out the old, reliable coatings such as like hard chrome or electroless nickel just yet. There’s no question that they still have their uses. Hard Chrome For example, hard chrome’s top advantage is that it has a hardness of 72 Rockwell C (RC) and is applied at the low temperature of 130oF. When applied in its purest form, it allows you to achieve any SPI finish on your tooling. Hard chrome is often a good choice for electrical circuitbreaker molds since they use materials containing as much as 40 percent glass. To help bat erosion and prevent severely damaging gates and surrounding mold areas, it is usually remend to use a highdiamond polish, followed by a hardchrome coating of to inches for added protection. The downside can be cost, since chrome plating is limited to areas accessible by an anode. If your mold has plex details, it could require extra conforming anode construction and that adds time and expense to the project. Another possible drawback is chrome’s environmental impact—chromium is a carcinogen. Some panies are attempting to develop better, cleaner alternatives, but so far nothing matches hard chrome’s benefits from a tooling perspective. Electroless Nickel Like hard chrome, electroless nickel has been used successfully for years, particularly to protect molds where corrosive offgassing is created by materials such as PVC or halogenated fire retardants. It is not unmon to see such resins produce an orange rust, corroding the unprotected mold almost right before your eyes. Products molded of such materials for the electronic or medical industry often cannot tolerate the presence of any oxidation byproducts. Electroless nickel does an excellent job of resisting oxidation because it plates very uniformly in thin deposits of to inches. Even in tight areas of detailed parts, electroless nickel at 50 RC hardness is ideal for corrosion protection. It can be deposit