Microstructure and Mechanical Properties of a Wear-Resistant As-Cast Alloyed Bainite Ductile Iron

doi:10.1007/s40195-014-0067-x

Abstract

Abstract:

An as-cast bainite ductile iron with excellent mechanical properties and wear resistance was fabricated by alloying and centrifugal casting method, and the alloyed chemical composition was optimized by using the thermodynamic software Thermo-Calc. By using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction, the microstructure of the as-fabricated bainite ductile cast iron was characterized pertinent to the elements distribution in matrix and features of ferrite and retained austenite. The results of mechanical properties test show that the hardness and compressive strength of this alloyed ductile iron are 52 HRC and 2,200 MPa, respectively.The as-cast bainite ductile iron possesses highly abrasive wear resistance and the reason can be ascribed to the solid solution of the elements Si, Ni, Cu, and Mn in the austenite and the formation of carbides of elements Cr and Mo. The strength of bainite ductile iron is increased by the acicular bainitic ferrite in the matrix.

Key words: Bainite ductile iron, Alloying, Microstructure, Abrasive wear resistance

Junjun Cui, Hongyun Zhang, Liqing Chen, Haizhi Li, Weiping Tong. Microstructure and Mechanical Properties of a Wear-Resistant As-Cast Alloyed Bainite Ductile Iron[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(3): 476-482.

Figures/Tables 11

Table 1 Chemical composition of the alloying ductile iron used in optimization (in wt%)

Alloy no.	C	Si	S	P	Mn	Mo	Ni	Cu	Cr	Fe
1	3.5	2.0	≤0.015	≤0.08	0.3	0.8	3.5	0.8	0.6	Bal.
2	3.5	2.4	≤0.015	≤0.08	0.3	0.8	3.5	0.8	0.6	Bal.

Fig. 1 Schematic illustration of the abrasion tester

Fig. 2 Calculated equilibrium phase diagram of bainite ductile iron containing 2.0 wt% Si

Fig. 3 Calculated equilibrium phase diagram of bainite ductile iron containing 2.4 wt% Si

Fig. 4 Microstructures of the bainite ductile iron a, its magnification b

Fig. 5 TEM micrographs and selected area electron diffraction patterns of the bainite ductile iron sample: a BF image; b electron diffraction pattern of ferrite; c DF image; d electron diffraction pattern of austenite

Fig. 6 XRD spectrum of the alloyed bainite ductile iron

Table 2 Summary of the XRD analysis for the bainite ductile iron

Lattice parameter of ferrite (a_α) (nm)	Lattice parameter of austenite (a_γ) (nm)	C content in austenite (wt%)	Volume fraction of austenite (%)
0.28664	0.36180	1.2	16

Fig. 7 Morphology and elements distribution in the matrix of the bainite ductile iron: a SEM morphology; b Cr; c Mo; d Cu; e Ni; f Si

Table 3 Comparison of the mechanical properties of the alloying ductile iron to high-chrome cast iron

Materials	Hardness (HRC)	Compressive strength (MPa)
As-cast alloyed bainite ductile iron	52	2,200
Commercial grade high-chrome cast iron	54–56	1,800

Table 4 Results of the wear test of the alloyed bainite ductile iron and 45# steel

Materials	Wear distance (m)	Loss of weight (g)	Relative wear rate (%)
45# steel	1,400	1.89	1.08
Alloyed bainite ductile iron	1,400	0.92	0.55

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