Correlation of mechanical properties with nondestructive evaluation of babbitt metal/bronze composite interface
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I.
INTRODUCTION
N O N D E S T R U C T I V E evaluation techniques have been studied in a variety of circumstances to assess their ability to characterize the mechanical properties of a particular material. One branch of the current research has focused on the use of ultrasonics or acoustic methods. From an engineering standpoint, the investigation and development of such nondestructive techniques are crucial in assuring the quality of a particular manufactured material. Consequently, ultrasonic methods have been studied in conjunction with the mechanical properties of a number of different substances, including various steels and aluminum alloys.I1-5] However, much less ultrasonic study has been conducted on other materials such as the group of soft tin alloys referred to as babbitt metals. In addition, comparatively less research has been done in the nondestructive evaluation (NDE) of the interfaces between two different metals.[6'7's] Because of the prominence of interfacial regions and the role they play in fracture mechanisms, the study of NDE techniques in this area is particularly important. In view of the potential industrial applications of NDE, the present study focuses on the ability of ultrasonic testing to predict the mechanical properties of the interface of the babbitt metal-bronze composite. In particular, the results of ultrasonic testing are correlated with strength, ductility, and microscopic examinations as well. Moreover, the microstructural characteristics at the babbitt-bronze interface were investigated using scanning electron microscopy and electron microprobe analyses.
II.
Table I. Mechanical Properties of the Bronze Backing Material -
Yield Strength (MPa) 103 *gage length = 5 cm
Tensile Strength (MPa) 207
Elongation* Pct 1.0
erties for this particular bronze. After casting, a thin layer of tin-lead alloy was deposited on the surface of the bronze in a solder tank at 360 ~ for 12 minutes. The pretinning chemical composition consisted of 0.03Bi, 0.08Cu, 0.5Sb, 40Sn, and balance Pb. Melted babbitt metal, composed of 0.10Fe, 0.35Pb, 3.5Cu, 8.0Sb, and balance Sn, was then poured over the pretinned bronze at a temperature of 474 ~ Thus, the final gland seal ring consisted of two layers, an outer bronze layer and an inner babbitt metal one. The width of the bronze portion was 3.7 cm while that of the babbitt section was 1.9 cm. The gland seal had an inner diameter (ID) of 39.4 cm, an outer diameter (OD) o f 52.7 cm, and a height of 5.1 cm. The half of the gland seal used in this investigation is shown in Figure 1. This figure also shows the location of the test specimens that were later fabricated to measure the bond strength of the babbittbronze interface. Figure 2 presents a cross-sectional view of the gland seal ring. B. Nondestructive Evaluation (NDE) Nondestructive examination of the babbitt-bronze composite interface was conducted by means of a computerized
EXPERIMENTAL PROCEDURES
A. Material All testing was conducted on a gland seal ring composed of the bronze-babbitt metal compo
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