Plasma arc surface modification of ASSAB 705 steel
Modification of steel surface by hardening process is traditionally done either by oxy-fuel, induction, laser or electron beam hardening. The technique using plasma arc which needed low initial cost is a new alternative for surface hardening. In this work, single and multiple pass of plasma arc was...
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| Format: | Thesis |
| Published: |
2006
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| Online Access: | http://eprints.uthm.edu.my/827/ http://eprints.uthm.edu.my/827/1/24_Pages_from_PLASMA_ARC_SURFACE_MODIFICATIONOF_ASSAB_705_STEEL.pdf |
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| Summary: | Modification of steel surface by hardening process is traditionally done either by
oxy-fuel, induction, laser or electron beam hardening. The technique using plasma arc
which needed low initial cost is a new alternative for surface hardening. In this work,
single and multiple pass of plasma arc was used to improve the hardness of ASSAB 705
steel surface. The variable parameters investigated were scanning velocity, operating
current, gas pressure and stand off distance. After single pass scanning treatment, four
types of surfaces were observed. They were fully-melted, partially-melted, non-melted
and inconstant-affected where each type of surface indicated different type of
roughness. This work has showed that scanning speed and operating current was
significantly influence the type of surface and roughness values. Analysis on nonmelted
surface after treatment gives maximum depth of hardened layer of about 186.7
um as well as hardness values of about 1100 HV50. It was also observed that the depth
of harden layer and hardness value was significantly decreases with increase in scanning
speed or with decreasing operating current. Microstructure analysis on hardened layer
also revealed the formation of martensite structure. Single pass scanning treatment
produced approximately 2 mm width of hardened surface. Larger area of hardened
surface could be produced by multiple pass scanning treatment. However the treatment
produced uneven hardness due to reheating effect on prior hardened layer. The results
from this work indicate that plasma arc is viable tool for surface hardening. |
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