Abstract:
Powder injection molding (PIM) is an attractive process to produce complex, near-net shaped components.
The process overcomes the shape limitation of traditional powder compaction, the cost of machining, the
productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting. Over 50% of the injection molded
and sintered components are made from stainless steel
composition [1–3]. The alloy 17-4 PH stainless steel
powders—a precipitation-hardening martensitic stainless steel, shaped and processed via injection molding
can achieve high complexity of part geometrical with
mechanical and corrosion properties, similar or superior to wrought material. Due to its high strength and
good corrosion resistance 17-4 PH has widespread applications, especially in medical, automotive, military,
and aerospace instruments [4–6].
Earlier investigations on PM or PIM 17-4 PH focused
on the effect of powder characteristics, sintering atmosphere, sintering temperature, sintering time, heat treatment, residual carbon content on microstructure, corresponding microstructural characterization, mechanical
and corrosion properties [4–6]. In several investigations
boron as a sintering additive has been used to achieve
higher sintered density in stainless steels at lower sintering temperatures [7–9]. As a consequence, a noticeable
improvement in the mechanical properties is obtained.
Boron can be added either in its elemental form (both
amorphous and crystalline) or as a compound (for example, Fe2B, BN, NiB, and CrB). A small particle size
of the additive is desirable to obtain a uniform dispersion. Boron additions increase hardenability in steels,
increase strength (via increase in sintered density), improve grain boundary cohesive strength, enhance corrosion resistance, and improve ductility [7, 9].
The aim of this study is to investigate the effect of
added boron on the sintering behavior and final properties of powder injection molded 17-4 PH stainless
steel. In this research, gas atomized 17-4 PH stainless steel powders (Fe-16.2Cr-4.6Ni-4.6Cu-0.54Mn0.30Nb-0.30Si-0.095Mo-0.038C-0.026P-0.002S) provided by Osprey Metals Ltd. were used. It has particle size distribution of D10 = 3.25 µm, D50 = 10.65
