Material Selection. The material systems currently in commercial use include ferrous alloys (low-alloy steel, stainless steels, soft magnetic alloys), nonferrous alloys (brass, bronze), tungsten carbide, pure nickel, electronic alloys (Invar, Kovar), and tungsten-copper composites. The physical and mechanical properties of several MIM engineering alloys (low-alloy steel and stainless steels) have been standardized by MPIF (Ref 10). | Fig. 9 Redesign of a MIM part to establish uniform wall thickness. Source Ref 8 Material Selection. The material systems currently in commercial use include ferrous alloys low-alloy steel stainless steels soft magnetic alloys nonferrous alloys brass bronze tungsten carbide pure nickel electronic alloys Invar Kovar and tungsten-copper composites. The physical and mechanical properties of several MIM engineering alloys low-alloy steel and stainless steels have been standardized by MPIF Ref 10 . After sintering the residual porosity in MIM parts is very low and not interconnected. With densities typically in excess of 96 of theoretical density the resultant mechanical properties are superior to conventional die-compacted P M materials and more closely match the properties of investment castings in similar alloys. Therefore the limitations discussed previously regarding the residual porosity in conventional die-compacted products do not apply to MIM parts. Secondary operations can be performed with no restrictions. References cited in this section 8. Powder Metallurgy Design Manual 2nd ed. Metal Powder Industries Federation 1995 10. Material Standards for Metal Injection Molded Parts Standard 35 1993-1994 edition Metal Powder Industries Federation 1993 Powder Metallurgy Methods and Design Howard I. Sanderow Management Engineering Technologies Powder Forging The design issues in P F are similar to the requirement of any precision closed-die forging. The difference is the starting preform in the case of P F the preform is a sintered powder metal part typically 80 to 85 of theoretical density with a shape similar to the final part configuration. By contrast in a precision closed-die forging the preform is a wrought steel blank with very little shape detail. Preform design for P F fabrication determines the extent of product shape detail required to meet the performance requirements of the finished P F part. Preform design is a complex iterative process currently modeled .
