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June 7th, 2019

Specifics of induction hardening of powder metallurgy (P/M) components

By Dr. Valery Rudnev

During the last decade, the use of advanced powder metallurgy (P/M) materials in several industries has been expanded at an impressive pace further penetrating markets of demanding applications; however, the biggest market for ferrous P/M components
remains to be the transportation industry, particularly the automotive and agricultural sectors. An ability to manufacture net-shape complex geometries offering competitive performance at an economical cost is an attractive feature of P/M parts (e. g. gears,
timing sprockets, cams, splined hubs, shafts, shock absorbers etc.) [1]. Density and porosity in the sintered compact are major factors affecting strength and hardenability of ferrous P/M materials; both properties have also been noticeably improved in the last decade. As an example, Fig. 1 shows a selection of P/M gears and gear-like components that regularly undergo induction surface hardening demonstrating impressive static and dynamic properties that closely approach respected properties fully dense wrought gearing materials.

Similar to steels, alloying helps enhance a desirable combination of strength, load-bearing capacity, ductility, and fracture resistance of P/M materials. Mo, Cu, Ni as well as Cr, Si, P, Mn are some of commonly used alloying elements in ferrous hardenable
P/M materials. Some of those elements provide critically beneficial synergistic effects. Carbon content is another major factor that
affects achievable hardness and strength. Recently developed lean P/M alloys preserve important performance characteristics of their higher alloyed counterparts and are also noticeably more homogeneous with minimized level of chemical segregation and dusting compared to P/M materials produced even 5–8 years ago.

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