Abstract
The machinability effects of new high-strength stainless
steels are researched due to specific properties arising
from their structure. In grinding operations, HIPed (Hot
Isostatically Pressed) austenitic 316L, duplex 2205 and
super duplex 2507, and as-cast 304 stainless steel, in
turning HIPed 316L, duplex stainless steel 2205 and X5
CrMnN 18 18 stainless steel, and in drilling HIPed PM
(Powder Metallurgic) Duplok 27 and duplex stainless steel
ASTM8190 1A and X2CrNi 1911 with HIPed NiTi coating were
researched in revised machining testing environments
using tool life testing, chip and workpiece surface
morphology analysis. Chips, workpiece surfaces and
cutting tools were analysed by SEM and EDS.
High toughness, workhardening and low heat conductivity
have a synergistic effect in inducing machinability
difficulties e.g. decreased product quality, shorter tool
life, increased power consumption and decreased chip
evacuation. An increased amount of alloying elements is
found to decrease machinability in the form of increased
cutting force and workhardening rate of the machined
surface, and decreased tool life and surface roughness.
Also, the machinability of PM-produced stainless steels
is decreased because of the increased amount of hard
oxide particles included in the microstructure of
PM-produced stainless steel. The formation of BUE
(Built-up Edge) is found, affecting the machinability and
tool life of tested high-strength stainless steels.
In grinding operations HIPed austenitic 316L and duplex
2205 stainless steel are rated according to cutting
force, workhardening rate and the amount of microvoids
and microcracks in ground surfaces. In turning operations
HIPed 316L, duplex stainless steel 2205 and X5 CrMnN 18
18 stainless steels are assessed in machinability order.
The machinability of conventional cast duplex stainless
steel ASTM8910 and HIPed duplex stainless steel Duplok27
were sorted according to the PRE-value (Pitting
Resistance Equivalent).
Finally in this study, the suitability of coated cemented
carbide tools in the drilling of conventionally produced
cast stainless steels with HIPed NiTi-coating was
investigated. In drilling of difficult-to-cut X2CrNi 19
11 stainless steel with a pseudo-elastic coating,
effective cutting parameters that maintain an adhesion
layer between the NiTi coating and the stainless steel
intact with an advantageous surface finish were
generated.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 20 Jun 2006 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-6853-2 |
Electronic ISBNs | 951-38-6854-0 |
Publication status | Published - 2006 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- stainless steels
- machinability
- machine tools
- wear
- surface coating
- grinding
- turning
- drilling
- nickel-titanium alloys