Question:
The secondary operation which is used to improve the self-lubricating capacity of the sintered part in powder metallurgy is
The secondary operation which is used to improve the self-lubricating capacity of the sintered part in powder metallurgy is
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Distinguish between the two pore-filling operations in powder metallurgy:
- Pores filled with Liquid Metal $\rightarrow$ Infiltration.
- Pores filled with Oil / Lubricant $\rightarrow$ Impregnation.
Updated On: Jul 4, 2026
- Infiltration
- Impregnation
- Repressing
- Coining
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The Correct Option is B
Solution and Explanation
Concept:
Powder metallurgy parts inherently retain interconnected porous networks after compacting and sintering. Various secondary treatments exploit or modify this porosity:
• Infiltration: Filling the pores of a lower-melting-point skeletal structure with a liquid metal of a lower melting temperature to improve mechanical strength and density.
• Impregnation: Filling the open, interconnected pores of a sintered part with a fluid substance such as oil, grease, or liquid polymers.
• Repressing / Coining: Pressing the sintered component in a closed die to achieve tighter dimensional tolerances or refine surface geometry.
Step 1: Relate porosity to self-lubricating capabilities. Sintered components like porous bearings and bushings require long working lives without external lubrication systems. To achieve this, the porous structural network is evacuated under vacuum and then submerged in a lubricating oil bath.
Step 2: Define the mechanism of Impregnation. The capillary action forces the lubricating oil deep into the interconnected pore voids. When the completed bearing operates in machinery, friction warms the assembly. The heat causes the oil to expand and draw out to the contact surface, establishing a continuous lubricating film. When motion stops, capillary forces draw the oil back into the pores. This process is called Impregnation.
• Infiltration: Filling the pores of a lower-melting-point skeletal structure with a liquid metal of a lower melting temperature to improve mechanical strength and density.
• Impregnation: Filling the open, interconnected pores of a sintered part with a fluid substance such as oil, grease, or liquid polymers.
• Repressing / Coining: Pressing the sintered component in a closed die to achieve tighter dimensional tolerances or refine surface geometry.
Step 1: Relate porosity to self-lubricating capabilities. Sintered components like porous bearings and bushings require long working lives without external lubrication systems. To achieve this, the porous structural network is evacuated under vacuum and then submerged in a lubricating oil bath.
Step 2: Define the mechanism of Impregnation. The capillary action forces the lubricating oil deep into the interconnected pore voids. When the completed bearing operates in machinery, friction warms the assembly. The heat causes the oil to expand and draw out to the contact surface, establishing a continuous lubricating film. When motion stops, capillary forces draw the oil back into the pores. This process is called Impregnation.
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