2
Procedure In Padan’s test,
quantities of nickel, Fe-V, Fe-Nb and Fe-Mo were added to the molten met-
al after it was poured into a ladle to produce the experimental alloys. Te metal was cast into standard test bars and given austempering treatment. Five alloys were studied in the
experiment, Alloy B with 1.4% nickel, Alloy V with 0.1% vanadium and 1.4% nickel, Alloy N with 0.043% niobium and 1.4% nickel, Alloy M with 0.3% molybdenum and 1.4% nickel and Al- loy U, a non-alloyed ductile iron (Table 1). Padan measured and recorded nodularity, nodule count, ferrite per- centage, tensile strength, yield strength, percent elongation and hardness values of alloys in the as-cast condition (Table 2). Te alloys were initially austenitized at 1,652F (900C) for an hour and aus- tempered at 635F (335C) for varying austempering times ranging from 0.5 to 180 minutes followed by air cooling. Following heat treatment, the alloys were again analyzed for mechanical properties and wear characteristics. When Padan observed that the
Table 1. Chemical Composition of the Ductile Irons Investigated Alloy
Chemical Composition
U B V N M
%C %Si %Mn %Ni %V %Nb %Mo 3.55 3.56
2.35
3.59 2.47 3.56 3.5
0.27
2.34 0.32 0.27
2.36 0.26 2.4
0.27
0.02 1.41 1.43 1.4
1.42
- -
0.1 -
-
- - -
0.043 -
Table 2. Mechanical Properties of the As-Cast Ductile Irons Investigated
Alloy Nodularity Nodule count /mm2
Matrix Ferrite (%)
Tensile Strenth (MPa)
U 85 - 90 200 65 - 70 548 B 85 - 90 256 60 - 65 568 V 85 - 90 N 85 - 90 M 85 - 90
240 246 242
30 - 35 30 - 35
microalloyed ADI Alloy V (0.1% vanadium) was more wear resistant than the other alloys investigated, he studied the alloy in further detail through SEM photographs (Figs. 1-4). He compared SEM photographs of Alloy V with the standard ADI Alloy M (0.3% molybdenum). Te photo-
Yield
Strenth (MPa)
675 694
25 - 30 645
363 470 494 519 528
Elongation (%)
12
10.4 7.14
6.42 3.7
Hardness (BHN)
179 195 236 226 263
graphs indicated the worn-out surface and oxide debris of Alloy V exhibit mostly the growth of oxides. Alloy M showed the presence of cracks and delamination of the worn-out surface, along with oxide layers formed at a few localized regions and metallic chips as wear debris.
- - - - 0.3
Figs. 1-4. SEM photographs were taken of ADI Alloy V to study the worn surface and wear debris during a wear test under 49.0 N load and compared to ADI Alloy M.
Nov/Dec 2012 | METAL CASTING DESIGN & PURCHASING | 43
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