Structural and Microhardness Changes After Turning of the AISI 1045 Steel for Minimum Quantity Cooling Lubrication

Radoslaw W Maruda,Grzegorz M Krolczyk,Szymon Wojciechowski,Mariusz Michalski,Piotr Nieslony

doi:10.1007/s11665-016-2450-4

Radoslaw W Maruda, Grzegorz M Krolczyk + Show 3 more

https://doi.org/10.1007/s11665-016-2450-4

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Abstract

This work presents the cooling effect under minimum quantity cooling lubrication and dry cutting on structural changes and microhardness of the ferritic-pearlitic AISI 1045 steel after turning. Due to the fact that the AISI 1045 steel has a two-phase structure, microhardness tests using the Vickers method were conducted with a load of 0.05 HV separately for ferrite and pearlite grains. The tests showed that cooling of the cutting zone under minimum quantity cooling lubrication (MQCL) condition decreased the depth of the hardened layer compared to dry cutting by approximately 40% for both pearlite and ferrite. Scanning electron microscopy analysis revealed that applying MQCL limits the formation of plastic deformations, among others, by reducing the surface crumple zone by approximately 50% compared to dry cutting. As a result of cooling being applied to the cutting zone using the MQCL method, the average diameter of ferrite grains has been decreased in the entire surface area compared to dry cutting. When using dry cutting, clear structural changes of the surface layer were also observed. This may be the result of sulfide inclusions which have formed, causing microcracks on the edge of the hardened layer and surface deformation visible as notches.

Highlights

Cutting methods significantly affect work efficiency and considerably affect surface integrity (SI) of the workpiece
Surface integrity in cutting processes depends on multiple factors, such as tool geometry, cutting parameters, temperature in the tool-workpiece interface and conditions of the cooling of the cutting zone
Microhardness and changes in microstructure in the surface layer appearing as microcracks, sulfide inclusions and deformations of the surface of the AISI 1045 steel after turning under various conditions of cooling were compared

Summary

Introduction

Cutting methods significantly affect work efficiency and considerably affect surface integrity (SI) of the workpiece. These changes are caused by high temperatures in the cutting zone which result in plastic deformation (residual stresses), chemical reactions taking place in the chip-tool interface and changes in the surface layer (microcracks, roughness) (Ref 1). Stresses are influenced by two factors: plastic deformation and changes in the volume of material related to temperature and metallurgic changes in the structure (Ref 3, 4). Research concerning the influence of the method of cooling the cutting zone during turning on creating SI is a very important issue, since SI analyzes the condition of the surface layer and its influence on functional and mechanical properties of the machined material (Ref 2). Industrial metrology is a broad field of science, and its proper application allows to obtain quality products (Ref 6-9)

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