With the introduction of high hardenability alloying additives such as chromium, manganese, molybdenum and nickel prealloyed into an iron matrix, the technique of sinter hardening (SH) in powder metallurgy (PM) enables the combination of both the sintering and heat treatment of structural PM parts into one processing step. Standard MPIF SH grade materials typically provide tensile strengths in the range of 450-1250 MPa (70-185 ksi). However, for demanding strength applications, the SH process also utilizes the method of copper infiltration (CI) during sintering to ensure sufficient mechanical properties. While CI generally enhances tensile strength, fatigue and ductility of the PM part, it can result in corrosion sensitivity, dimensional inconsistency, and is also costly. Conversely, a newly developed hybrid processing method, which comprises partial CI with subsequent post sinter vacuum impregnation by an inorganic sealant (IS) compound has proven to be a cost-efficient alternative to sealing residual porosity of the SH parts while simultaneously improving final mechanical characteristics and corrosion properties.
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