Influence of surface pores on selective laser melted parts under lubricated contacts: a case study of a hydraulic spool valve

ABSTRACT

Hydraulic valve spools can be produced with hollow structures using SLM to increase dynamic response. The contact between the valve spool and body is crucial and relates to the performance of a hydraulic valve, which has not been studied. This paper investigates the reciprocating contact of an SLM-fabricated spool valve from a tribological aspect. By varying the process parameters, porous and standard spool samples (18Ni-300 steel) were produced using SLM. The lubricating behaviours of 18Ni-300 samples under various contact pressures and reciprocating frequencies were investigated in comparison to a real spool sample (hardened 38CrMoAl steel) using conventional manufacturing. The results indicate that the standard SLM 18Ni-300 spool sample has comparable tribological performance compared to the conventional manufactured 38CrMoAl sample. The SLM fabricated sample, with a number of large pores, has the highest friction coefficient under a wide range of contact conditions due to rough surfaces and cracks. Compared to the standard sample, the presence of a few small pores positively affects lubrication by providing local extra lubrication and serving as debris containers. Such an effect becomes very notable under low pressure, reducing the friction coefficients by half.

KEYWORDS:

• Selective laser melting
• hydraulic valve
• pores
• lubrication
• friction

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Dr. Y. Zhu is an associate professor at the State Key Laboratory of Fluid Power and Mechatronic Systems of Zhejiang University in China. He received his Ph.D. from Royal Institute of Technology, Sweden. He is also the associate editor of ASME Journal of Tribology. His research interests include surface design in metal additive manufactured parts and the AM driven product design, particularly in hydraulic components.

Y. Yang is a Ph.D. student from the State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, China. His research area is enhancing wear resistance of SLMed surfaces.

P. Lu a Master student from the State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, China. His research area includes lubricating behaviours of SLMed surfaces.

X. Ge a Master student from the State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, China. His research area includes lightweight design of hydraulic components using SLM.

Prof. H. Yang is a professor at the State Key Laboratory of Fluid Power and Mechatronic Systems of Zhejiang University in China. He is Academician of Chinese Academy of Engineering and a board director of Global Fluid Power Society (GFPS). His research interests include fluid power transmission and control and intelligent manufacturing.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant numbers 51890881 and 51775486], National Key Research and Development Program of China [SQ2018YFB200029-04], and the Zhejiang Province Qianjiang Talent Program [QJD1702027].