Vitro-Lube NPI-1220                 Vitro-Lube NPI-1220C                 NPI-14, NPI-16 & NPI-425                  
                                  Intended Use & Suggested Applications   |    Design Details   |    Wear Life Testing

Appearance

In its finished form, Vitro-Lube is similar in appearance to more conventional dry film lubricant coatings. It is dark gray to black with a matte finish. It is a continuous smooth coating that burnishes readily when handled.

Thickness

The nominal thickness is 0.0005 to 0.0009 inches of which two thirds is the base coat and one third is the top coat.

Cure Cycle

The heating cycle required to bond the Vitro-Lube base coat to the metal surface is critical and consequently very precise. In order to soften the ceramic frit and allow proper bonding, the surface of the coated part is brought to a temperature of +975°F and held for one minute. This is accomplished in high heat recovery kilns in an oxygen atmosphere.

Failure to reach the proper temperature will prevent adequate softening of the ceramic frit causing a total lack of adhesion. Excessive time at temperature can result in burning of the coating which causes a degradation of the coating and a loss in wear life. The top coat is subsequently applied over the base coat and cured for one hour at +300°F for the NPI-1220 and +575°F for the NPI-1220C.

Contaminants

For optimum results, contamination of the Vitro-Lube coated bearing surface should be avoided. Abrasive substances such as sand or metallic powder (from grinding) will definitely shorten the wear life of the coating. Fluids of any type that are on the coated surface during motion of the part will seriously degrade the wear life of the coating. This is true of all known dry film lubricant coatings and Vitro-Lube is considered to be less affected than most other dry films. The coating will withstand immersion in all fluids common to aircraft and space vehicles without washing off. No significant damage will result provided the fluids are removed prior to use.

Some fluids used in typical machining operations are especially harmful to the coating and extreme care should be taken whenever any type of machining is contemplated on parts that have been coated with Vitro-Lube (such as machining of outer races of swaged plain spherical bearings).

Metal Substrate Selection

The selection of a compatible material to accommodate Vitro-Lube has never posed a problem as it lends itself to almost all metals common to the airframe and engine industry today. For best results, we suggest a hard, reasonably smooth surface (RHR 32) that in itself possesses the required corrosion resistance.

Clearance

When mating parts of an assembly are to be coated with Vitro-Lube, such as a plain journal bearing and its mating shaft, a minimum clearance of .0005" should be maintained. The end of the shaft and the inside edge of the bushing should be radiused to facilitate assembly without damage to the Vitro-Lube coated wear surface.

Environment

Vitro-Lube was originally developed for a maximum temperature environment of 630°F; however, we feel it is within its capabilities to be specified for environments up to 900°F, although wear life will be significantly reduced. It has been exposed to cyrogenic temperatures and sodium vapors with no apparent deleterious effect. Vitro-Lube has an established compatibility with the space environment as it remains stable in hard vacuum; it does not volatilize or outgas. Vitro-Lube has been certified as non-impact sensitive.

General Design Suggestions