Effect of die temperature on mechanical properties of hot pressed P/M

نویسنده:
, ,
سال
: 2010
چکیده: In conventional warm compaction, both powder and die are heated to a certain temperature during

compaction. This is a technique for producing P/M compacts with higher green and sintered strength as

compared to room temperature pressing. However, there is a certain limit to powder temperature due to flow

problems at higher temperatures. Heating the die above this practical limit can further improve properties. In

this work, the effect of die temperature on green and sintered properties of Astaloy CrM powder has been

investigated. Here, the powder at 135 oC was fed to the die at different temperatures. Density and strength

for samples in green and sintered conditions were evaluated for two compaction pressures of 500 and

650MPa and temperatures ranging from ranging from 135 to 165 oC. Comparison of samples compressed at

room temperature showed marked improvement in density and strength properties. A 22% increase in

density, as well as 40% increase in green strength was observed. Tensile and impact strengths were

improved by about 10% and 20% respectively. SEM micrographs showed more rounded pores and hence

reduced stress raising sites. The improvement in properties can be mainly attributed to changes in powder

morphology and die wall lubrication due to migration of hot lubricant from interparticle space to die walls. The

latter will reduce particle spacing and bring about more intimate metal-metal contacts as well as better

lubrication on die walls.
کلیدواژه(گان): Powder metallurgy,Warm compaction,Sintering,Mechanical properties
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