final me 488 peer reviewed lit

8/11/2019 Final ME 488 Peer Reviewed Lit

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Ben Kahut

June 8, 2012

ME 488

Abstract: This is a peer-reviewed article review. This review will be of the article,

Tensile and impact behaviour of sinter-forged Cr, Ni and Mo alloyed powdermetallurgy steelsfound in theMaterials and Design Journaland available online

March 20, 2009. The authors of this article were D. Shanmugasundaram and R.

Chandramouli. This article will include: a short introduction and background section, a

summary or description of the original work reported, a short review of the technical field

that the article is a part of, analysis of references and how they relate to the main article, a

clear identification of the original contribution this article makes to the field, and

references to the articles in the form of footnotes or endnotes.

There are obvious advantages of Powder Metallurgy (P/M). These advantages are

summarized by Randall M. German, in his book Powder Metallurgy and Particulate

Materials Processing,that include: cost, properties, and reactivity. The inability to make

materials in any other fashion typically raises this notion of P/M. However, sometimes

products can be made using manufacturing methods such as forging or machining, but the

work needed to provide the product is too cumbersome. P/M is an alternative to deflect

cost while not compromising material properties, thus maintaining consumer safety.

In this article, research was performed on correlating the tensile and impact behavior of

sinter-forged chromium (Cr), Nickel (Ni) and Molybdenum (Mo) alloyed powder metals

with the failure mode and microstructure. The article starts with an introduction that lets

the reader know how the porosity left over after the pressing and sintering of P/M alloys

plays a major role in mechanical behavior [1,2,3]. It is also explained how porosity ofsintered alloys can be dramatically reduced with a post forging process [4,10]. Next, the

experiment details are laid out so one can repeat this research if necessary. The raw

materials are listed as purchased, including: atomized iron powder ~150m size, graphite

powder ~5m size, and Ni, Cr, Mo ~100m size. The mixing of the powders were

mixed in a pot mill for 10 h. Size of compaction and pressure are given to reach a green

density of 94-96% using a graphite lubrication. A sintering temperature of 1000 C was

used. Then, immediately after sintering, the compacts were hot forged repeatedly and

drawn into a bar. Standard tensile and impact specimens were machined out of these bars

with densities near theoretical. Microstructure and fracture surfaces were achieved using

a standard microscope with image analyzer and a SEM respectively.

Results were based on five different powder compositions: Fe-0.2%C, Fe-0.2%C-1%Cr,

Fe-0.2%C-1%Cr-2%Ni, Fe-0.2%C-2%Ni, and Fe-0.2%C-2%Ni-1.5%Mo. For ease of

discussion, the alloys will be named Powder Alloy (PA) 1-5:

PA-1: Fe-0.2%C

PA-2: Fe-0.2%C-1%Cr

PA-3: Fe-0.2%C-1%Cr-2%Ni

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PA-4: Fe-0.2%C-2%Ni

PA-5: Fe-0.2%C-2%Ni-1.5%Mo

PA-1 displayed the lowest ultimate tensile strength (UTS), yield strength (YS), and

hardness (HRB) values. As expected, PA-1 displayed the highest elongation (% EL),

reduction in area (%RA) and impact strength. Fracture images from the SEM show a

purely ductile failure.

Conversely, PA-2 displayed the highest UTS, YS, and HRV values while having the

lowest %EL and %RA and impact strength values [8]. The microstructure of this alloy

displayed ferritic structure with Cr carbides and numerous bainites, which accounts for

the increased tensile and hardness values. Failure type is a mixed mode, brittle and

ductile features were present.

PA-3 has lower, but comparable, properties to the results of PA-2. This decrease in UTS,

YS, and HRB and increase in %EL, %RA, and impact strength can be attributed to the

addition of Ni. Ni is an austenite stabilizer that improves impact resistance of steels [7].

The microstructure contained a ferrite-bainite structure with retained austenite. A failure

mode similar to PA-2 was present.

PA-4 cements the notion that Cr increases UTS, YS, and HRB in conjunction with the

fact that Ni improves impact resistance in steels. A ferritic microstructure was observed

with bainites on the grain boundaries. Some retained austenite was also observed. A

mostly ductile failure mode was observed.

PA-5 had Mo added to the alloy to have a positive effect on UTS, YS, and HRB, while

having a negative impact on %EL, %RA, and impact strength [6,9]. Looking at the

microstructure shows why this phenomenon occurs. Mo carbides are formed in thisferrite and bainite microstructure [5,11]. This impact is still approximately half as much

as the presence of Cr makes on the alloys mechanical properties. A mixed mode of

failure was observed having both brittle and ductile features.

A very interesting detail was mentioned in this article. It was stated, that the tensile

strength values of all the five sintered and forged steels were comparable with that of

commercial low-alloy wrought steels of near- similar compositions. This statement,

although small is size, presents a huge topic. In the past, if a P/M process was selected as

the process for a given application, then a compromise would probably be made. A

compromise of the structures mechanical properties would be made in order to cut cost

due to precision manufacturing and speed of completion. However, if a P/M structurecan be made with comparable properties, it is a no brainer what process to use.

Therefore, the contribution to this field is two-fold. It presents manufactures five types of

alloyed steel that have been sinter-forged with representative microstructures and

properties to leave nothing in doubt what a given element will do to an alloy. The article

also provides manufacturers the comfort to know, when similar processes are followed,

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there is no compromise in structural integrity when using this P/M process compared to

other steel processes [12, 13,14].

This is the kind of knowledge this field wants in the articles it presents for prospective

followers. This peer-reviewed literature was placed in the Materials and Design section

to help inform and improve processes. Materials and Design is always a forward movingnotion that always wants better. Inefficiencies and failures always arise, which leads to

the questions: Can new materials be produced? Or, can a better design be produced?

Scientists and engineers will always contribute to such journals because it is always

necessary to go forward and improve.

There were 14 references cited in this article. Provided are the references, as cited in the

article, and the contributions made to bridge any gaps of knowledge for both the author

and prospective readers from research that has already been completed to new research:

[1] Danninger H, Jangg G, Weiss B, Stickler R. Microstructure and mechanical properties

of sintered iron Part I basic considerations and review of literature. Powder Metall Int

1993;25(3):1116.

Contribution(s) Made: This literature was not found online. However, contribution is

summarized as providing existing knowledge in P/M on the relationship between

microstructure and mechanical properties. A good engineer does not remember

everything he/she ever learned, but knows where to find the knowledge in order to

complete the task at hand. This is a case of existing literature being available and the

authors gaining knowledge in order to know where they are going (comparable to

learning history).

[2] Danninger H, Jangg G, Weiss B, Stickler R. Microstructure and mechanical propertiesof sintered iron Part II experimental study. Powder Metall Int 1993;25(4):1703.

Contribution(s) Made: This literature provides knowledge that the mechanical properties

are very sensitive results of the impact of sintering parameters. These properties are

linked to %EL and impact energy. These parameters give the authors insight on how to

yield positive data in their experiment. This knowledge probably saves the research

project a lot of headaches (time, cost, error, etc..).

[3] Danninger H, Jangg G, Weiss B, Stickler R. Microstructure and mechanical properties

of sintered iron Part II experimental study. Powder Metall Int 1993;25(5):21923.

Contribution(s) Made: This literature provides knowledge that the mechanical properties

are very sensitive results of the impact of sintering parameters. These properties arelinked to %EL and impact energy. Again, These parameters give the authors insight on

how to yield positive data in their experiment. This knowledge probably saves the

research project a lot of headaches (time, cost, error, etc..).

[4] Wang MC. Properties of high density powder forged iron based alloy. Powder Metall

Int 1994;37(3):2015.

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Contribution(s) Made: Wangs work provides evidence that forging will give higher

mechanical properties than sintering will. This is one of the foundations of the article

(hence, the title). Therefore, a sinter-forging process should likely yield close to

theoretical density. Which, was proven in this article.

[5] Straffelini G, Fontanari V, Molinari A. Influence of microstructure on impactbehaviour of sintered ferrous materials. Powder Metall Int 1995;38(1):4551.

Contribution(s) Made: This literature provides evidence of the influence of Mo in alloys

Microstructure and impact properties. Mo and diffused carbon will form Mo carbides to

account for the brittle nature of an alloy with Mo. Mo was one of the elements compared

as an alloying element to see impact on mechanical properties and microstructure. The

knowledge this literature provides gives the authors an idea on the effects that Mo will

have in their experiment.

[6] Molinari A, Straffelini G, Campestrini P. Influence of microstructure on impact and

wear behaviour of sintered Cr and Mo steel. Powder Metall Int 1999;42(3):23541.

Contribution(s) Made: The impact and wear behavior of sintered Cr and Mo steels were

studied with a conclusion of Cr improving mechanical properties of steel. This is done

through solution hardening and carbide formation. Similar to Mo above, this literature

includes Cr as well as Mo. The carbide information backs up the mechanical information

provided in this article. If carbides are known to form, then UTS and YS should increase

with %EL, %RA, and impact strength decreasing.

[7] Phillips RA, King JE, Moon JR. Fracture toughness of some high density PM

steels. Powder Metall Int 2000;43(1):438.

Contribution(s) Made: The presents of Ni in an alloy helps retain austenite. This article

also provides the notion that sintered alloys could have similar properties of wroughtalloys. As stated above, this information provided is huge. The authors will use the

knowledge provided in this literature to know what properties to expect their P/M

research.

[8] Krehl Michael, Rau Gunter. Application of P/M materials in synchronizer-rings.

In: Euro PM2000 applications; 2000.

Contribution(s) Made: This literature shows how mechanical properties are increased in

alloys when Cr is added in the combination of sintering. Again, similar to Mo above,

little is in question when data is already provided. The authors are bridging the gap of

various literature articles to compile and complete their research.

[9] Hwang KS, Hsieh CH, Shu GJ. Comparison of mechanical properties of Fe

1.75Ni0.5Mo1.5Cu0.4C steels made from PIM and press and sinter processes.

Powder Metall Int 2002;45(2):1606.

Contribution(s) Made: Could not find article. The literature appears to have various data

from different P/M processes. This information was probably used to determine best

sintering parameters. Again, These parameters give the authors insight on how to yield

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positive data in their experiment. This knowledge probably saves the research project a

lot of headaches (time, cost, error, etc..).

[10] Zhang Z, Frisk K, Salwen A, Sandstrom R. Mechanical properties of FeMoMn

SiC sintered steels. Powder Metall Int 2004;47(3):23946.

Contribution(s) Made: This literature shows the highest tensile strength is in the processof sintering forged low alloy steels. This sinter-forged process is the basis of the article

in review. The literature provides evidence to the authors of what a sinter-forge process

can provide. Some similar elements were alloyed so some comparisons can be made in

research.

[11] Candela N, Velasco F, Martinez MA, Torralba JM. Influence of microstructure on

mechanical properties of molybdenum alloyed P/M steels. Int J Mater Process Technol

2005;168:50510.

Contribution(s) Made: This literature shows how Mo positively impacts tensile and yield

strength in low alloy P/M. This knowledge provided the author with data of one of the

elements used in their research. Obvious, advantages are extracted from data and

knowledge already provided.

[12] Danninger H, Pottschacher R, Bradac S, Salak A, Seyrkammer J. Comparison of

Mn, Cr and Mo alloyed sintered steels prepared from elemental powders. Powder Metall

Int 2005;48(1):2332.

Contribution(s) Made: The comparison of Mn, Cr and Mo alloyed sintered steels show

that the alloys are suitable for multi use precision applications. Overview is given from

the authors of the article in review that shows what kind of P/M products are used today.

Information from this literature was used in doing this overview.

[13] Chandramouli R, Kandavel TK, Shanmugasundaram D, Ashok Kumar T.

Deformation, densification and corrosion studies of sintered powder metallurgy plain

carbon steel preforms. Int J Mater Des 2007;28:22604.

Contribution(s) Made: Deformation and densification studies were made on Fe-C P/M

alloys. Microstructures of cold and hot upsetting were examined. Flow stresses were

found to impact densification. This process gives the authors of the article in review

knowledge of microstructures based on the process done in this literature. Again bridging

the gap of existing knowledge to better understand the results of their research.

[14] Shanmugasundaram D, Chandramouli R, Kandavel TK. Cold and hot deformation

and densification studies on sintered FeCCrNi low alloy P/M.Contribution(s) Made: Deformation and densification studies were made on Fe-C P/M

alloys as well as the addition of alloying elements Ni and Cr. Microstructures of cold and

hot upsetting were examined. This process gives the authors of the article in review

knowledge of microstructures based on the process done in this literature. Again bridging

the gap of existing knowledge to better understand the results of their research.

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I found this article, Tensile and impact behaviour of sinter-forged Cr, Ni and Mo

alloyed powder metallurgy steelsfound in theMaterials and Design Journal, to be

very interesting. The fact that P/M processes can produce comparable mechanical

properties, leaving no compromise, should lead to a continuation of P/M increasing

popularity in processing options.

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final me 488 peer reviewed lit

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