The conventional powder metallurgy industry identified achieving full density by a single compaction step as one of the key technical goals in the P/M Vision and Roadmap. This program will attempt to structure a systematic approach toward achieving that goal through development efforts in powder technology, compaction systems (tooling, lubrication and compaction technique) and sintering. The achievement of ultra-high green density has been demonstrated by several researchers for an elemental powder using a simple tool geometry. The goal of this program is to take those achievements and apply them to industrial alloy steel powders, using advanced commercial compaction methods and a complex part geometry, such as a gear or sprocket with a part length >25 mm with an upper limit of 100 mm. Issues that will need to be addressed include:        

Powder—low-alloy steel powder base with an equivalent hardenability to AISI 8620, need for internal lubrication vs. die-wall lubrication, type/amount of graphite addition, maximum compressibility for the powder, special lubricants (type and amount), shape/size of fine powder additions, activated additions.

 Tooling—new tool designs configured for ultra-high compaction pressures, selection of tool materials, use of tool coatings, die-wall application of lubricant

 Compaction systems—ultra-high pressure compaction, high-velocity compaction, warm compaction, evaluate effect of aspect ratio (length:diameter), uniform die filling,              

Initial studies will focus on one base powder (selected on the basis of compressibility and hardenability), three compaction approaches (warm, ultra-high-pressure, and high-velocity) three lubrication methods (die-wall, special/proprietary, and standard Acrawax) and two sintering methods (conventional - 1,140°C in 90 nitrogen/10 hydrogen and high temperature - approximately 1,280°C in vacuum and atmosphere).  The goal for Phase 1 is to reach/exceed 7.5 g/cm³ in sintered or heat treated condition; for Phase 2, to apply the concepts in Phase 1 to a multi-level part and reach 7.7 g/cm³ final density; for Phase 3, to take the technology to 7.8+ g/cm³ and perform complete product testing. Intermediate testing in Phases 1 and 2 will include tensile, impact, and fatigue in the carburized condition. Ultimate goal is to replace carburized 8620 wrought steel products, especially transmission gears.

 Status

The preliminary program plan was approved at the spring 2004 CPMT meeting.  New funding sources are being identified and a program leader (Bill Jandeska) selected for kick-off during the second half of 2006. A SPFD Task Force planning meeting was held in Detroit March 24, 2006, to review the program alternatives and get volunteers on board for the first phase of the program. Four sub-tasks were in identified and are discussed in the following sections.

 Sub Task 1: High Velocity Compaction (HVC)

Task members – North American Höganäs, Gasbarre Products, Burgess-Norton, Böhler-Uddeholm, JIT Tool & Die

The tooling is being prepared by Burgess Norton using tool steel provided by Böhler-Uddeholm.  Adaptors were purchased from JIT.  The Hydropulsar HVC press located at Gasbarre Products has been modified for both conventional and warm compaction.  Powder has been provided by NAH.  Once the tooling is completed (scheduled for late May-June 2007) the first evaluation studies will be run.    

 Sub Task 2: Warm Compaction – Traditional using GRI-STBF Tool Set

Task members – Hoeganaes Corporation, Alpha Sintered

One of the previously manufactured CPMT STBF tool sets was shipped to Alpha Sintered for modification and adaptation to fit their press.  Five different Hoeganaes warm compaction powders were prepared and warm compacted using this tool set.  Green densities in the 7.4 g/cc range were achieved.  Following sintering and heat treatment metallurgical and mechanical properties will be measured to characterize the response of the various processing treatments (second half 2007).      

 Sub Task 3: Warm Compaction – Effect of Part Length

Task members – Hoeganaes Corporation, Cloyes Gear, Capstan, FMS Corporation

A Honda 17 tooth sprocket was selected as the product application since it is currently in wrought steel.  Warm compaction tools were purchased from JIT Tool.  The tools were run at Capstan-Atlantic using both Hoeganaes and QMP low alloy steel powders.  Three different parts lengths – 7, 11 and 22 mm were prepared.  Half were sintered in a conventional belt furnace and the other half will be high temperature sintered.  Following sintering the sprockets will be heat treated and then performance tested by Cloyes using a special sprocket bench tester (second half 2007).    

Sub Task 4: Ultra High Pressure Compaction – CIP

Task members – QMP, Inco, Ametek, Abbott Furnace, Horizon

A new ultra high pressure compaction technology (greater than 100 tsi) using cold isostatic pressing methods was used to prepare two low alloy steel blends and one tool steel powder.  Compacts measuring 40 mm diameter by 150 mm long were pressed.  Both powder systems achieved higher green densities than normally seen by conventional compaction methods.  Following conventional and high temperature sintering the low alloy steel materials will be machined into test specimens and tested for tensile, impact and contact fatigue properties (second half 2007). 

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