Development of superplastic boronizing using duplex stainless steel

Hasan, Rafidah (2006) Development of superplastic boronizing using duplex stainless steel. Masters thesis, University of Malaya.

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Superplastic boronizing (SPB) is a new surface hardening technique utilizing the ultra high plasticity phenomenon in metal in carrying out boronizing process in which boron atoms are diffused into the metal substrate to form hard boride layer.In this research, a new method of SPB process was introduced and the results obtained were compared with the one conducted using the normal conventional boronizing (CB) method. Thermo-mechanically treated duplex stainless steel (DSS)with fine grain microstructure and can show superplastic behavior at high temperature was used as the superplastic material. As for comparison data, CB process was conducted on coarse microstructure as-received DSS as well as on the fine microstructure thermo-mechanically treated DSS samples. Boronizing processes were conducted at temperatures of between 1123 - 1223 K and time of 1 - 6 hours. All of the boronized specimens demonstrated the thin, smooth and compact morphology of boride layer. For the same experimental condition, the boride layer thickness for CB was in the range of 8 μm - 40.7 μm, while for SPB, it was within 10 μm - 46.2 μm. Dual phases of FeB and Fe2B were detected on the boride layer of conventionally boronized DSS.Whereas, on the boride layer of superplastically boronized specimen, only the favorable single phase of F e2B was detected. For conventionally boronized coarse and fine microstructure DSS, the surface hardness were in the range of 608 HV - 2311 HV and 720 HV - 2601 HV, respectively. Surface hardness for superplastically boronized DSS showed significantly higher value in the range of 847 HV - 2914 HV. The activation energy determined from SPB process was found to be the lowest at 186.2 kJ mol-1,compared to 192.1 kJ mor 1 and 224 .5 kJ mor 1 for CB of fine and coarse microstructure DSS respectively. The overall results from the study show that the SPB process can significantly improve the surface properties ofDSS as compared to the CB.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Boriding
Subjects: T Technology > T Technology (General)
T Technology > TS Manufactures
Divisions: Library > Tesis > FKM
Depositing User: Mohd. Nazir Taib
Date Deposited: 30 Nov 2015 02:46
Last Modified: 30 Nov 2015 02:46
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