IPMD 14th Edition 2010-2011, 9 pages, 5103 words

Author: Dr David Whittaker, DW Associates, 231 Coalway Road, Wolverhampton WV3 7NG, United Kingdom

Powder Metallurgy (PM) has come a long way, since it took its first tentative steps, around 70 years ago, into simple, single-level shaped (structural) parts from its previous staple product of self-lubricating bearings. Dr David Whittaker updates some of the advances that have been made in PM materials, shape complexity and also mechanical properties.

There are two principal reasons why PM might be chosen as the preferred route for the production of a specific engineering component:

1. Some characteristic of the product (eg. combination of chemical constituents, control over microstructure, controlled porosity etc.) can be created, by starting from a powder feedstock, which would be otherwise impossible (or, at least, very difficult) to attain. (“Product uniqueness”)
   
2. PM is the most cost effective of a number of possible options for the process route. (“Product cost effectiveness”)

There are some structural component applications, which rely at least partly on the former of these reasons, but, in the vast majority of applications, the latter reason drives the selection of PM.

Advances in structural part production have therefore been largely driven by the desire to enhance achievable complexity of shape, in order to maximise cost advantage (through enhanced material utilisation and reduced energy intensity) particularly compared with other process routes involving finish machining.

Increasingly, over the past decade or so, new markets have also been captured by improving the properties and performance levels of PM products. The PM industry’s response to the latter of these driving forces is covered in the feature “Advances in high performance PM automotive components”, also published in the IPMD 14th Edition 2010-2011 which focuses on high strength, high performance automotive PM parts.

Developments in materials, processing equipment and process technologies have all contributed to these advances. This article will refer briefly to the historical developments in all of these areas, but will concentrate on the more recent developments. Advances in quality control issues and in PM structural parts standards will also be considered, followed by a review of current markets and applications.............

Further sections of this article include:

• Powders
  - Improved compressibility
  - Alloying techniques: mixes
  - Prealloyed powders
• Stainless steels/light metals
• Process technology
• Quality control
• Properties and standards
• Products and markets
• References

Figures and Tables:

Fig. 1 Density improvements over the past 40 years achieved by die compaction of iron-based powders

Fig. 2 Increases in heat treated ultimate tensile strength of ferrous PM materials

Fig. 3 Diffusion bonded planetary carrier produced by Hitachi Powdered Metals, Japan. Used in a continuously variable transmission (CVT), this component was produced from two parts – an output boss with legs and a hub, which were assembled in the green state and then diffusion bonded during the sintering process (Courtesy JPMA)

Fig. 4 PM Aluminium camshaft bearing cap, made by Metal Powder Products Co. for General Motors Powertrain (Courtesy MPIF)

Fig. 5 PM Aluminium vane for motorbike power steering damper made by Fine Sinter Co Ltd, Japan (Courtesy JPMA)

Fig. 6 VVT System Stator produced by PMG Füssen GmbH, Füssen, Germany for its customer Schaeffler Group Automotive, Hirschaid, Germany (Courtesy MPIF)

Fig. 7 Rotor for petroleum fuel storage pump produced by Lovejoy Sintered Solutions LLC, of Downers Grove, USA, for Petrotec– India (Courtesy MPIF)

Fig. 8 Sintered Fe-Ni-Cu gear from variable geometry turbo for a diesel engine, produced by Mitsubishi Materials PMG Corporation, Japan (Courtesy JPMA)

Fig. 9 VVT sprocket produced by Cloyes Gear & Products Inc., Paris, Arkansas, USA used in a variable valve timing (VVT) system in a high-performance V-6 engine (Courtesy MPIF)

Fig. 10 Breakdown of PM applications in European cars

Fig. 11 PM sleeve for a synchronising unit in a light truck 5 speed manual transmission gearbox, produced by PMG Füssen GmbH, Füssen, Germany (Courtesy EPMA)

Fig. 12 Energy efficient gear pump rotors with newly developed tooth profiles used in automotive oil pumps, produced by Sumitomo Electric Industries Ltd (SEI), Japan (Courtesy JPMA)

Fig. 13 Long, thin-walled helical gear with

Fig. 14 Sintered Cu-Ni-Sn-C-P bearings used in exhaust gas flow regulation valve, produced by Hitachi Powdered Metals Co Ltd, Japan (Courtesy JPMA)

Fig. 15 High density PM transfer case slide sleeve used in 4WD SUV’s, produced by Federal Mogul Sintertech SAS of Veurey-Voroize, France (Courtesy EPMA)

Table 1 Mechanical properties of selected aluminium PM alloys (Source: Aluminium Association, USA)

Table 2 Tensile strength for range of ferrous PM materials from ISO 5755:2001

Table 3 Fatigue and elastic constant data for selected PM steels from ISO 5755:2001