Microstructure of a Steel Sprocket and Anodizing

AluminumIan Buchanan and Kris Magri

Santa Rosa Junior College

Engr 45, Younes Ataiiyan

December 07, 2009

Authors

• Ian Buchanan is a Civil Engineering major, hoping to work in construction

• Kris Magri is a Mechanical Engineering major who plans to work in robotics

Part I: Microstructure of a steel sprocket

Imperfections, carbon content, and banding

Sprocket

Courtesy of Motorcycle Spares, accessed on 11/27/09http://www.te-motorcyclespares.co.uk/images/Chain%20&%20Sprocket.jpg

Procedure

• Desired cuts

• Mounted in bakelite

• Sanded and polished

• Nitric acid solution (Nital) etch

• Observe and report

Smooth surface?

Sprocket, valley between teeth

Carbon Content

Sprocket, bottom of tooth

-estimated as 0.3 to 0.6% carbon

-using chart from materials lab

Banding

.35%C steel, hot-rolled, courtesyW.C. Leslie, The Physical Metallurgy of Steels, 1981

Steel sprocket

Mn and C Segregation

• For cast steels, Mn segregates into a branched structure that flattens out upon hot rolling

• Mn blocks C in austenite • Pearlite forms at concentrated areas of Mn

and C

X-ray photographs

courtesyW.C. Leslie, The Physical Metallurgy of Steels, 1981

Mn Branching After rolling

Banding Anisotropy

“Peeling”

Sprocket, top of tooth

courtesyW.C. Leslie, The Physical Metallurgy of Steels, 1981

-1045 steel

-heat treatment

-baked on paint

from SunStar Products http://sunstar-mc.com/Products.aspx under steel - off-road/mx/street. accessed on 11/27/09

Damascus Steel

• Hard steel with a water-like appearance from layers of differing carbon content

• Unlike banding, different phases are macroscopically visible

• Bars of steel repeatedly doubled over and forge welded to achieve differing layers

Modern pattern welded damascus steel, knife blade, from http://damascus.free.fr/f_damas/f_quest/i_steel/dmsc_k_.jpg

Banding and Anisotropy

• fracture happens parallel to the bands in tensile sample

• Stainless steel with the banding microstructure

Courtesty of A C Stauffer, D A Koss, J B McKirgan. “”Microstructural Banding and Failure of a Stainless Steel”. Metallurgical and Materials Transactions: A : Physical Metallurgy and Materials Science. Warrendale: Apr 2004. Vol. 35A, Iss. 4; pg. 1317, 8 pgs

References• W.C. Leslie, The Physical Metallurgy of Steels, 1981• Damascus steel. ( 2009). In Encyclopædia Britannica. Retrieved December  2,  2009, from Encyclopædia

Britannica Online: http://search.eb.com/eb/article-9028636• A C Stauffer, D A Koss, J B McKirgan. “”Microstructural Banding and Failure of a Stainless Steel”.

Metallurgical and Materials Transactions: A : Physical Metallurgy and Materials Science . Warrendale: Apr 2004. Vol. 35A, Iss. 4; pg. 1317, 8 pgs