Low Pressure Injection Molded Tungsten Carbide

As an engineer or end item user, have there been times that you have had a severe wear problem? You know that the problem could easily be solved by using tungsten carbide, but the geometry of the part is such that pressing, preform, or extruding can not be used. Low Pressure Injection Molded (LPM) Carbide from Retco Tool Co., Inc can be your solution. The near-net shape capabilities of injection molding are well known in the plastic, ceramics and metal industries but until the last few years tungsten carbide parts have been thought to be “undo-able.“ Near –net shape LPM carbide parts are here. The geometric shapes that can be addressed with LPM, but not with other process’ are almost limitless. Retco is a fully integrated facility that has been in business for 40 years. Five years ago, we established our own low pressure injection molding department to provide complex geometric shapes for use in the wear parts industry. The synergy from powder to molding to final fabrication is a valuable tool in the development of new products specified by our customers. The savings to Retco’s customer due to the lower cost start-up and tooling costs has created a healthy partnership. Retco’s ability in tungsten carbide grade development has led to the development of tungsten carbide wear grades with a Rockwell A hardness of <95.0 using Ultra grained powder. LPM is ideal for the short run of less than a 1000 parts and can be tooled up for long runs. The Process The process consists of placing Tungsten Carbide grade powder with an organic binder in a double planetary mixer. The powder and binder are then mixed until it is a homogenous plastisol. The parts are then molded in aluminum tooling, 90% of which is built in-house. The control of the green density when compounding the powder is critical. Tungsten Carbide can shrink from 20 – 30% when sintered and the tooling is built with appropriate shrinkage allowances built in. We control the green density to insure that all tolerances are met. The part, after molding, is inspected before being dewaxed. At this point in the process the part can be reverted and re-melted for use as another part if any deficiencies are found. The parts are then placed in a organic media and thermally de-waxed. By using an organic binder and organic de-binding media, we do not have any EPA problems. The media and binder can both be disposed of in the local landfill. The parts are then sintered in a vacuum furnace. After sintering, the parts are evaluated metallurgically. For critical porosity call-outs, the parts are then Hot Isostatic Pressed. The Material Retco currently produces parts using a 41/2% Co ultra grain material, a 41/2% Co sub-micron material, a 6% Co sub-micron material and a 12% Co coarse grain material. (see table 1)

The Material
Retco currently produces parts using a 41/2% Co ultra grain material, a 41/2% Co sub-micron material, a 6% Co sub-micron material and a 12% Co coarse grain material. (see table 1)