J. O. AGUNSOYE ET AL. 25
tenite transformation to martensite causes increased sur-
face hardness and less wear rate loss. Carbon content
plays a significant role in chromium carbide formation
and its morphology as well as hardness, impact tough-
ness and wear resistance. In this study, the effect of car-
bon content on the microstructure, mechanical proper-
ties and wear characteristics of HC-Wi has been studied
and compared to the Hadfield steel.
2. Materials
HC-Wi and Hadfield Steel grade of materials were pro-
duced in Nigerian Foundries Limited (NFL), Otta, Nige-
ria using the charge makeup in Tables 1 and 2 respec-
tively. An Electric Induction Furnace of 500 kg neutral
lined was used for the melting operation and the sample
representative taken from the molten bath at 1550˚C d
and poured into a CO2 sand improvised moulds (11 × 11
× 200) mm. The charge makeup used in obtaining the
specification is tabulated below.
After the first heat from Ta ble 1, a sample representa-
tive was taken and casted. For subsequent batches, fine
granules of graphite were added in their various compo-
sitions of 1.6% C, 2.2% C, 2.7% C and 3.3% C respec-
tively to the molten bath and the temperature maintained
at 1520˚C - 1543˚C for 10 minutes to enable the graphite
granules dissolve adequately. This process was repeated
Table 1. Charge makeup for HC-Wi.
Elemental Contribution (%)
Raw Materials Mass (Kg) C Si Mn P S Cr
Returns 156.25 0.94 0.21 0.01 0.01 0.017.19
Steel Scraps 223.21 0.09 0.09 0.04 0.02 0.020.00
Fe-Cr 98.21 0.10 - - - - 17.68
Fe-Si 2.23 - 0.33 - - - -
Fe-Mn 4.46 0.07 - 0.58 - - -
Graphite 3.80 0.51 - - - - -
Total 500 1.55 0.63 0.63 0.03 0.03 24.87
Table 2. Charge makeup for Hadfield Steel.
Elemental Contribution (%)
Charge makeup
for Hadfield
SteelRaw Material
Mass
(Kg) C Si Mn P S Cr
Returns 187.83 0.410 0.190 4.760 0.005 - 0.570
Steel Scraps 234.80 0.095 0.120 0.120 - - -
Fe-Cr 7.04 0.001 - - - - 1.280
Fe-Si 2.00 - 0.300 - - - -
Fe-Mn 63.40 0.140 - 9.640 - - -
Graphite 4.93 0.66 - - - - -
Total 500 1.30 0.610 14.52 0.005 0.0001.850
for all incremental granules addition. To reduce the ten-
dency for oxidation, 1 Kg of Aluminum Briquette was
added to the melt. Besides, Hadfield steel melt was pre-
pared according to ASTM 128 C standard as presented in
Table 2.
The overall chemical composition obtained for the 2
heats and 5 batches is presented in Table 3.
A calibrated Hilger Analytical Direct Optical Emission
Polyvac Spectrometer E980 C with 20 analytical channe ls
was used for the analysis of the chemical composition of
the HC-Wi and Hadfield steel. Hadfield steel is difficult
to machine due to its work-hardening propensity. Hence,
a sample representative was taken from the Hadfield
steel molten bath and poured in to a (10.20 × 10.2 × 200)
mm preheated medium carbon steel mould so as to obtain
the required (10 × 10 × 50) mm bar for the impact test.
This technique was aimed at avoiding the need to ma-
chine the samples. To investigate the effect of the heat
treatment of Hadfield steel on the properties of HC-Wi,
halves of all the specimens with the size (10 × 10 × 50)
mm were solution annealed at 1050˚C for 30 minutes and
then water quenched.
2.1. Microstructure
For microstructural analysis, all the as-cast and heat-treat-
ed samples were cut from the bottom end, ground with
tehrapol-31, then polished using a colloidal suspension of
0.04 µm silicon dioxide and then etched in 100 ml alco-
hol and 3 ml HNO3 acid after polishing using Allegrol
with diamond suspension at the Metallographic Labora-
tory, Department of Mechanical Engineering of the Uni-
versity of Ot t a wa , Ca nada. A metallurgical optical m icro-
scopy was used to study the microstruc tures.
2.2. Mechanical Properties
Vickers micro hardness of tested samples was measured
using Duramin-1 microhardness tester struers. The re-
ported hardness values were the average of five meas-
urements. Charpy unnotched impact test was also carried
out on (10 × 10 × 50) mm standard Hadfield and HC-Wi
specimens at room temperature. In order to compare the
wear resistance of the developed HC-Wi alloys with
Hadfield steel, abrasive wear tests were conducted on all
Table 3. Chemical composition of the HC-Wi.
MaterialCMnSiCrP S Mo Ni AlFe
HC-Wi-11.550.630.6324.870.03 0.03 0.02 0.01 0.01Balance
HC-Wi-22.220.630.6224.600.03 0.03 0.01 0.01 0.01Balance
HC-Wi-32.730.590.6024.200.03 0.03 0.01 0.015 0.02Balance
HC-Wi-43.260.560.6023.600.03 0.03 0.01 0.01 0.02Balance
Hadfield
Steel 1.3014.520.611.850.01 0.00 - - 0.15Balance
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