PSI - Issue 23

Golta Khatibi et al. / Procedia Structural Integrity 23 (2019) 475–480 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 3. (a) Ultrasonic fatigue testing system, (b) geometry of the fatigue samples, (c) and an image of the sample with coupling tip.

3. Results and discussion

3.1. Microstructure The microstructure of the welded area of two sample series are shown in Fig. 4a,b and 4c,d. The microstructure of the both samples consists mainly of a martensitic matrix with finely distributed TiC carbides and retained austenite. Sample C appears slightly less homogeneous, less martensitic with higher content of retained austenite. Occasionally larger TiC particles and Cr enriched regions are observed in both cases which can be seen in the SEM images shown in Fig. 4b and d. Due to the different processing routes of the welding wires, mainly the different ingredients used such as ferroalloys and carbides used to form TiC in the weld, the microstructure of C-series contains a higher proportion of austenite leading to a slight decrease in their hardness. Micro-hardness measurements resulted in values of 658±44 and 711±35 HV for C and E samples respectively.

TiC

Fig. 4. Optical micrographs and SEM images of the microstructure of the weld overlays: (a,b) E-series and (c,d) C- series respectively.

3.2. Wear test

The results of combined impact/abrasion tests on the two types of welds are presented in Fig. 5a and their corresponding macroscopic views before and after the second test run are shown in Figs. 5b and c. There are no