ACHIEVING LIGHTWEIGHT, WEAR RESISTANT STEELS THROUGH NITRIDING


A low cost heat treatment method could improve the wear resistance of austenitic manganese and aluminum steels.


LAURA BARTLETT AND SABRA SERINO, TEXAS STATE UNIV., SAN MARCOS, TEXAS H Fe


Steel A Steel B Steel C


Bal. Bal. Bal.


Steel A


Phase AlN


AlN


Oxide layer Oxide layer Oxide layer


igh manganese and aluminum austenitic steels have been intensely investigated in recent years for their potential applications in military and transportation industries. T ese steels have exceptional combina- tions of high strength and toughness with excellent wear resistance. Adding aluminum in levels between


6% and 8.8 wt% reduces the steel’s density by 10% to 15% compared with quenched and tempered chromium and molybdenum steels. But it also decreases strain hardening and abrasive wear resistance. Metalcasting researchers have discovered that wear resistance may be improved in these steels through a low-


Table 1. Chemical composition of alloys in weight percent Alloy


C


0.90 0.89 0.94


Si


1.07 1.56 1.57


Mn


30.42 29.97 30.22


cost case hardening heat treatment in a nitrogen atmosphere (nitriding) that produces a hard surface layer of aluminum nitride (AlN). Low density high manganese and aluminum steels are being con- sidered for use in tough and wear resistant automotive components and ballistic armor plating. These steels could be considered light-


P


0.001 0.002 0.001


Table 2. EDS chemistry of microconstiutants in weight percent Steel


Treatment


Steel A Matrix between AlN plates Steel C


Steel C Matrix between AlN plates Steel A Steel B Steel C


1,000C 6hrs 1,000C 6hrs 1,100C 8hrs 1,100C 8hrs 900C 8hrs 900C 8hrs 1,100C 8hrs


Fe


Bal. Bal. Bal. Bal. Bal. Bal. Bal.


32 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2015


S


0.006 0.007 0.012


Mo


0.54 0.53 0.61


Ni - -


0.011


Al


8.83 8.81 5.98


Cu


0.006 0.006 0.010


Si -


2.0 -


1.3


2.4 5.4 -


Mn -


54 -


53 36 30 17


O


< 4 -


< 4 -


31


36 40


N


31 -


34 -


5.8 - -


Al 64


0.3 63


0.3 14


23 33


Mo - - -


0.51 - - -


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62