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Technical Data Sheet - K1014


>>>Discontinued on December 31, 2004, see Process K1228 as the alternative, was discontinued to ensure RoHS compliance.

ABSTRACT

Commonly known as "Aluminum Chromate" or "IVD" coating, process K1014 has been gaining popularity with Neodymium Iron Boron magnets due to its ability to be an extremely strong oxidation inhibitor. Magnetic Component Engineering offers this process for all grades of NdFeB magnets. The coating has been found to pass salt spray tests and it is economical in large quantities; small quantities can be expensive since the process is very involved and includes multiple set-ups. Typical industries that have started using this type of coating include the Aerospace, Military hardware, motor (commercial and military), sputtering, and the computer industry. The coating is suitable for vacuum applications. The process is given below to give an idea of how this is carried out; however, it must be noted that certain pre-processing steps to enhance adhesion and retard oxidation that are carried out at MCE are considered proprietary and not available for disclosure.

CLEANING

As in most metal finishing operations, preparation of the substrate is vital if good adhesion is to be achieved. To remove oil, grease, or machine lubricants, vapor degreasing with a chlorinated solvent is normally employed. From this point, operatives no longer handle components without protective plastic and cotton gloves, thus avoiding contamination of the substrate.

GRIT BLASTING

To remove surface contamination and provide a suitable "key" for adhesion of the ivadized coating, components are grit blasted with pure aluminum oxide abrasive. The substrate surface is very active at this point, and will readily absorb and retain gas or moisture. For this reason, it is important to lead components into the vacuum chamber within 4 to 6 hours of grit blasting. Residues of aluminum oxide are removed with dry filtered air of nitrogen.

LOADING

Small components are loaded into stainless steel barrels, which rotate during the coating cycle. Larger components are jigged by hooks or wire onto a rack, which is supported and then inserted into the vacuum chamber by means of a steel frame mounted on four legs known as the "dolly."

FINAL PREPARATION & COATING

After components have been loaded into the vacuum chamber, air is evacuated by a series of pumps to a pressure of 10-5 Torr. Once this pressure is achieved, the chamber is backfilled to 10-3 Torr with Argon. The anode consists of a number of crucibles manufactured from Boron Nitride or Diboride. A dc potential is applied to the substrate in the order of 1000 to 1400 volts, with the substrate (cathode) being negatively charged. The collision between electrons and the Argon gas molecules results in ionization of the Argon and the subsequent release of more electrons. The bombardment of the cathode produces a secondary emission of electrons, so an avalanche effect is achieved. This process will continue until a self-sustaining discharge is achieved.

Sputtering will occur at the surface of the substrate where atoms of the substrate will be dislodged through momentum transfer. During this process, surface contamination such as grit particles will also be removed; after a period of 15 to 20 minutes of plasma cleaning, the substrate can be coated.

COATING

Each anode crucible is fitted with a wire feed unit, and when a high current is applied, the resistive heat generated melts the aluminum wire, which is subsequently vaporized in the high vacuum. Once evaporated, the aluminum atoms are ionized, then attracted to, and finally deposited on the substrate.

UNLOADING

Unloading is a simple operation using the dolly.

SHOT PEENING

This process uses a pressure blaster with a glass bead media at a pressure of 20 to 30 psi. Shot peening "densifies" the coating and reduces porosity, yielding a hard uniform coating which will readily accept an additional corrosion preventative coat of chromate, epoxy paint, etc. Special extraction equipment ensures that shattered glass particles are removed, thus avoiding damage to the aluminum coating.

INSPECTION

Micrometer and ring gauges are used to check tolerances on coated components with magnetic permascope devices checking coating thickness. Visual inspection of all components is essential to determine presence of scratches, nodules or inclusions/foreign bodies in the coating as well as possible damage through incorrect handling or overheating during the coating operation.

Table 1 MIL-DTL-83488

Class

Thickness

Salt Spray in hours
Type I/TypeII

Class 1

25 microns

504/672

Class 2

12.5 microns

336/504

Class 3

7.5 microns

168/336

Type I : Without Chromate Conversion
Type II: With Chromate Conversion

 

  1. When process K1014 is required, the most common is Process K1014 per MIL-DTL-83488 Rev D Type II Class 2.
  2. Note that this specification was formally MIL-C-83488 Rev C Notice 1.