Influence of minimum quantity lubrication parameters on grind-hardening process

ABSTRACT

Currently, dry grind-hardening has been studied to achieve a deep grinding harden layer. For dry grind-hardening process, the ground surface may have a poor surface quality. In our previous research, minimum quantity lubrication (MQL) has been proved as an effective way to improve the surface quality in grind-hardening process. Unfortunately, the relationship between the surface quality and parameters of MQL is still not clear. In this paper, different spraying parameters (fluid flow, air pressure, nozzle location, spraying distance) are investigated in surface grinding experiments of annealed steel AISI 5140. Grind-hardening performances are analyzed for grinding force and surface quality, such as surface roughness, micro-hardness, and grinding harden layer depth. Consequently, the results show that MQL can improve the grinding surface roughness and the micro-hardness of the grinding harden layer. The surface roughness can be improved with a better lubrication, which can be achieved with the appropriate spray direction. The surface roughness and the harden layer depth are reduced with the increasing fluid flow rate and air pressure, while they increase with the spraying distance.

KEYWORDS:

• Experimentation
• grind-hardening
• harden
• layer
• micro-hardness
• MQL
• roughness
• surface/subsurface

Acknowledgments

The authors would like to acknowledge the financial supports from the National Natural Science Foundation of China (Grant No. 51475158 and 51275436), and Foundation of Hunan Provincial Key Laboratory of High Efficiency and Precision Machining of Difficult-to-Cut Material (Grant No. E21430).