Introduction

RESIN IMPREGNATION is a process that eliminates or reduces internal porosity of castings and P/M parts by saturating internal voids with liquid resins. The process has been practiced for many years on castings and P/M parts, and resin impregnation has, to a large extent, eliminated macroporosity (pore diameter >125 ."m ) in castings. With further process improvements and low-viscosity resins capable of good penetration, impregnation is also capable of significantly reducing microporosity (pore diameter <125 /'m ) (Fig. 1).

Fig. 1 Microstructure of P/M iron with impregnated resin in microporosity. 200x

The most common purpose of resin impregnation is to produce leak-tight parts. However, impregnation also:

• Enhances corrosion resistance

• Prepares porous surfaces for subsequent surface treatments or coatings

• Improves machinability

Depending on the product and application, sealant penetration can be minimal or deep, with interconnected porosity reduced up to 90%. When the application is preparation for surface finishing or plating of the part, penetration is usually minimal. It is much deeper for parts that need pressure retention and are machinable, including rugged hydraulic components for industrial pumps. Depth of penetration is controlled by the process time and exposure during impregnation, resin type, and the structure of the internal porosity.

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