Nickel Alloys Applications and Processing

8/10/2019 Nickel Alloys Applications and Processing

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NICKEL ALLOYS APPLICATIONS

AND PROCESSINGISSUES TO ADDRESS... How are metal alloys classified and how are

they used? What are some of the common fabrication

techniques? How do properties vary throughout a piece of

material that has been quenched, for example? How can properties be modified by post heat

treatment?


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Classifications of Metal Alloys


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Stationary gas turbines suchas this are used for flexible powergeneration. Energy efficiencyincreases as the turbine operatingtemperature increases; so the need

is for nickel-based alloys that arecapable of performing for longperiods at high temperatures. Someblades in this turbine operate atabove 650 degrees Celcius.Special nickel-based alloys arealso used to make critical high-temperature parts of turbines inaircraft jet engines


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Nickel-containing stainless steels are increasingly used to constructrail carriages. Choice of nickel-containing stainless steel allows thedesign of low-weight structures with sufficient impact resistance to giveimproved passenger safety in the event of a crash. The corrosionresistance of stainless steel also permits attractive designs and lower

maintenance costs.


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This Toyota Prius is one of a new breed of automobiles called

"hybrids." these combine an efficient conventional engine with arechargeable nickel-containing battery. Hybrids have much loweremissions and better energy efficiency than conventional vehicles.Because they need no speical infractructure investiment, theirbenefits can be realized now. (Photo courtesy of Toyota Corp.)


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The most commonly-used material for high-quality bathroom andkitchen fittings is brass that is plated with nickel, usually with a thinktop layer of chromium. The photos above show nickel-chromium-plated shower parts. Nickel- and chrome-nickel-plated surfaces arevery attractive and very hard-wearing. They have long useful lieves,being able to withstand the aggressive cleaning associated withbathrooms and kitchens.


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Low Alloys: Low Carbon Composition : less than ~ 0.25% C

Microstructure : ferrite and pearlite Properties : relat ively soft and weak, but possess high

ductility and toughness Other features : moderately priced , machinable and

weldable Applications : auto-body components, structural shapes,sheets etc.

Plain c arbon s teels : residual concentration of impurities are unresponsible to heat treatment

High -s t reng th low al loy (HSLA) steels: up to 10 wt% ofalloying elements, such as Mn, Cr, Cu, V, Ni, Mo can bestrengthened by heat-treatment


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Examples of HSLA Steels : Weath ering s teels , exhibit superior atmospheric corrosion

resistance Contro l-ro l led s teels , has a highly deformed austenite

structure that transforms to a very fine equiaxed ferritestructure on cooling

Pearli te-redu ced steels , strengthened by very fine-grainferrite and precipitation hardening with a little or no pearlitein the microstructure

Microal loyed s teels , with very small additions of Ni, Vand/or Ti for refinement of grain size and/or precipitationhardening

Ac icular ferr i te s teel , very low carbon steels with sufficienthardenability to transform on cooling to a very fine high-strength acicular ferrite structure


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High-Alloy Steels: Stainless Steels (SS) The primarely alloying element is Cr (11 wt.%) Highly resistance to corrosion Four major classes:(a) The austeni t ic SS has -Fe microstructure at roomtemperature!! This fcc structure normally stable only above910 C is stabilized in SS by addition of Ni extremely

corrosion resistant and NOT magnetic;(b) The ferr i t ic SS has Fe bbc structure. Not so corrosionresistant as austenitic SS, but less expensive magnetic steel;(d) The martens i t ic SS this fine magnetic bct structure isproduced by rapid quenching and possesses high yieldstrength and low ductility. Applications: springs.(e) The prec ip i tat ion harden ing SS producing multiplemicrostructure form a single-phase one, leads to theincreasing resistance for the dislocation motion (a) and (b) are hardening and strengthening by co ld w o rk


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Nickel Alloys Applications and Processing