PNNL

Abstract

While PIM has been used with great success in manufacturing a wide variety of metal products, including those made from stainless steel, nickel-based superalloys, and copper alloys, it has found limited application with reactive metals such as titanium. This is because traditional PIM binder systems typically employ high volume fractions of thermoplastic or thermoset polymers. As a result, depending on the debindering procedure one or more problems can develop, including the introduction of residual carbon into the final sintered part and/or poor control and reproducibility in the final shape and dimensions of the component. Recent development of binder systems utilizing polyacetals that can be decomposed catalytically offer the potential for cleaner binder removal. However, they also require expensive capital equipment to handle the acidic vapor catalyst and the volatile decomposition products that subsequently form. Researchers at Pacific Northwest National Laboratory (PNNL) have developed an alternative approach that employs an aromatic compound as the primary binder constituent. The aromatic can be easily and cleanly removed by sublimation and requires only a small amount of a secondary additive to ensure adequate handling strength in the part after primary de-binding.