Issue 70

P. Sahadevan et alii, Frattura ed Integrità Strutturale, 70 (2024) 157-176; DOI: 10.3221/IGF-ESIS.70.09

1. EDAX analysis confirms the composition (Fe: 71.7%, Cr: 18.44%, Ni: 3.86%, Cu: 3.51%) of 17-4 PH SS in printed parts. The powdered particles exhibited annular morphology and displayed an average size of 30 ± 5 μ m. 2. LP of 300 W melted all metal powders to produce parts with minimal or no defects, resulting in better tensile strength in the SLM parts. A higher SS of 1000 mm/s ensure better fusion characteristics, ensuring all metal powders melt and fill pores (present, if any) to produce better strength in-built parts. Lower and higher HD showed adverse effects on UTS. The LP, SS and HD contributions on UTS were 78.42%, 18.7% and 2.88%. The LP: 300 W, SS: 1000 mm/s, and HD: 0.1 mm produced the highest UTS equal to 1206 MPa. 3. Higher WR was recorded at a lower LP of 240W, attributed to the unmelted metal particles inside the pores. A higher SS of 1000 mm/s raise the metal temperature to cause a dense molten pool and has a greater probability of remelting the already solidified layers to fill pores present, if any, in part. The melt pool becomes unstable due to inadequate melting due to reduced heat input with increased HD beyond the critical value of 0.08 mm, resulting in higher WR. The optimal condition for a low wear rate of 41.23 ± 1.7 µm is achieved in SLM parts for the process variable set at LP: 300 W, SS: 1000 mm/s, and HD: 0.08 mm. 4. The super-ranking concept determined the optimal condition for multiple outputs (UTS and WR). LP was found to have a dominant effect with the highest contribution, equal to 81.01%, followed by SS and HD, equal to 18.66% and 0.33%. SRC determined optimal conditions (LP: 300 W, SS: 1000 mm/s, and HD: 0.12 mm), resulting experimentally in the WR and UTS equal to 47.65 ± 1.9 µm and 1197 ± 5.3 MPa. 5. The fracture surface morphology of 17-4 PHSS samples at different conditions indicated different failures. 17-4 PHSS samples LP1SS1HD1 condition (LP: 240 W, SS: 600 mm/s, and HD: 0.08 mm) displaying ductile-brittle fracture followed by LP3SS3HD2 and LP3SS3HD3 conditions displaying ductile failure. 6. The variation in wear patterns, seen by comparing the conditions LP1SS1HD1, LP3SS3HD1, and LP3SS3HD3, underscores the complexity of wear mechanisms and the significant influence of manufacturing parameters on material wear characteristics. Specifically, the increase in hatch distance from 0.08 mm in LP3SS3HD1 to 0.12 mm in LP3SS3HD3, keeping the laser power and scan speed constant, suggests that even small changes in processing parameters can have noticeable effects on the wear resistance of 17-4 PHSS samples at different conditions. [1] Garrison, W.M. (1990). Ultrahigh-strength steels for aerospace applications, JOM, 42, pp. 20-24. DOI: 10.1007/BF03220942. [2] De Nisi, J., Pozzi, F., Folgarait, P., Ceselin, G. and Ronci, M. (2019). Precipitation hardening stainless steel produced by powder bed fusion: Influence of positioning and heat treatment, Procedia Struct. Integr., 24, pp. 541-558. DOI: 10.1016/j.prostr.2020.02.048. [3] Ravitej, S.V., Murthy, M. and Krishnappa, M. (2018). Review paper on optimization of process parameters in turning Custom 465® precipitation hardened stainless steel, Mater. Today: Proc., 5(1), pp. 2787-2794. DOI: 10.1016/j.matpr.2018.01.066. [4] Mróz, M., Kucel, B., R ą b, P. and Olszewska, S. (2023). Study of the TIG Welding Process of Thin-Walled Components Made of 17-4 PH Steel in the Aspect of Weld Distortion Distribution, Materials, 16(13), pp. 4854. DOI: 10.3390/ma16134854. [5] Gholipour, A., Shamanian, M. and Ashrafizadeh, F. (2011). Microstructure and wear behavior of stellite cladding on 17-4 PH stainless steel, J. Alloys Compd., 509(14), pp. 4905-4909. DOI: 10.1016/j.jallcom.2010.09.216. [6] Bressan, J.D., Daros, D.P., Sokolowski, A., Mesquita, R.A. and Barbosa, C.A. (2008). Influence of hardness on the wear resistance of 17-4 PH stainless steel evaluated by the pin-on-disc testing, J. Mater. Process. Technol., 205(1-3), pp. 353 359. DOI: 10.1016/j.jmatprotec.2007.11.251. [7] Ghaffari, M., Nemani, A.V. and Nasiri, A. (2022). Microstructure and mechanical behavior of PH 13–8Mo martensitic stainless steel fabricated by wire arc additive manufacturing, Addit. Manuf., 49, pp. 102374. DOI: 10.1016/j.addma.2021.102374. [8] Zai, L., Zhang, C., Wang, Y., Guo, W., Wellmann, D., Tong, X. and Tian, Y. (2020). Laser powder bed fusion of precipitation-hardened martensitic stainless steels: a review, Metals, 10(2), pp. 255. DOI: 10.3390/met10020255. [9] Sarkar, S., Kumar, C.S. and Nath, A.K. (2017). Effect of mean stresses on mode of failures and fatigue life of selective laser melted stainless steel, Mater. Sci. Eng. A, 700, pp. 92-106. DOI: 10.1016/j.msea.2017.05.118. R EFERENCES

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