An attempt is made to modify the surface metallurgically and enhance the wear resistance of AISI 316LN austenitic stainless steel using friction stir processing. Friction stir welding tools made up of tungsten based alloy with pin and pinless configuration was used. Fine equiaxed grains were observed in the friction stir processed zone irrespective of tool configuration used. Dry sliding wear resistance was evaluated using pin-on-disc wear tester and it is found that, the friction stir processed zone showed superior wear resistance compared to the base metal. Microstructure, micro hardness, and worn surfaces were used to correlate the results obtained.
An attempt is made to reduce the process forces and tool wear during friction stir welding of 409M ferritic stainless steel and to enhance the mechanical properties by induction preheating of base metal with different preheating temperatures at the leading of tool. It is observed that the preheating significantly decreased the longitudinal and axial forces. Tool degradation analysis was carried out to find out the loss of tool profile and material. Mechanical properties especially impact toughness values were increased due to significant reduction in the tool wear.
Dissimilar metal welds between austenitic stainless steels and chromium molybdenum ferritic steels are being widely used in many elevated temperature applications. The austenitic stainless steel (316LN) with superior creep strength and oxidation resistance are required in the higher temperature regions while creep resistant ferritic steels like 9Cr-1Mo steels (P91) are commercially more attractive for the lower temperature sections in liquid metal reactors. This work employs thermal imaging during tensile deformation of laser welded P91-316LN dissimilar weldments for early detection of necking and failure zones. Infrared thermography in combination with uniaxial tensile testing has been widely used for characterization of weldments. This technique can be used in characterizing dissimilar welds which exhibits peculiar behavior during tensile deformation. A fast array based thermal detector was used to map the temperature distributions which reveals the stress concentration was primarily along 316LN base material, but later moved towards P91 side. This clearly portrayed that the tensile elongation of P91 steel was inferior to 316LN stainless steel and the primary fracture location was observed at P91 base material. It also confirmed that the weld zone was comparably stronger than the parent materials.
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