Microstructural Investigation on Failure of Internal Drive Shaft
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Microstructural Investigation on Failure of Internal Drive Shaft M. K. Karthikeyan Æ R. K. Gupta Æ V. Rajesh Æ B. R. Ghosh Æ P. P. Sinha
Submitted: 20 May 2007 / in revised form: 10 October 2007 / Published online: 21 November 2007 Ó ASM International 2007
Abstract 17-4 PH stainless steel is used as internal drive shaft material in liquid engine pumps. One of the drive shafts failed during operation. The shaft pieces were in contact for short duration after failure, which has resulted in abrasion of fractured surfaces. Samples from the location of failure were taken, and investigation of the failure was carried out using optical and scanning electron microscopy. The microstructural analysis of the material and fractographic analysis of the fractured surface show that the failure was caused by excessive torsion. Keywords
17-4PH Stainless steel Torsion failure
Introduction Precipitation-hardened (PH) stainless steels are finding increasing use as structural materials in variety of applications in chemical, aerospace, and nuclear industries. These steels possess excellent corrosion resistance and have very good mechanical properties for demanding applications. Depending on the stability of austenite at ambient temperatures, these steels are classified as martensitic, semiaustenitic, and austenitic grades. Hardening is derived by precipitation, hence the designation PH. The precipitation-hardened martensitic stainless steels are used for their high strength and good corrosion resistance. These alloys form a low-carbon martensite with martensite finish (Mf) temperatures just above room temperature [1].
Martensitic grades PH steels usually contain 4 to 5% Ni along with copper, molybdenum, aluminum, titanium, and niobium added to increase the strength of alloy. 17-4 PH and 15-5 PH martensitic grades are commonly used in fabrication of aerospace systems. These are strengthened by precipitation of copper rich phases in a martensitic matrix [2–4]. One of the components, internal drive shaft of liquid engines made of 17-4 PH in H900 temper condition, failed during a performance test (Fig. 1), and parts of the shaft were in contact for some time after failure. The contact resulted in abrasion of the fracture surface and masking of the fracture features. Detailed metallographic and fractographic analyses have been done to determine the causes of failure. The paper presents the analysis of fracture features and microstructure of the shaft material.
Chemistry and Mechanical Properties of Material The alloy was arc melted followed by vacuum arc remelting and heat treated to H900 temper. The chemical composition of the alloy is as given in Table 1. The typical mechanical properties of the material in H900 temper are given in Table 2.
Experimental Microstructural Observation and Hardness Measurement
M. K. Karthikeyan R. K. Gupta (&) V. Rajesh B. R. Ghosh P. P. Sinha Mechanical Engineering Entity, Vikram Sarabhai Space Centre, Trivandrum 695022, India e-mai
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