Elsevier

Wear

Volume 269, Issues 11–12, 28 October 2010, Pages 699-708
Wear

Diamond tools wear and their applicability when ultra-precision turning of SiCp/2009Al matrix composite

https://doi.org/10.1016/j.wear.2009.09.002Get rights and content

Abstract

The wear pattern and its mechanisms of single crystal diamond (SCD) and polycrystalline diamond (PCD) tools have been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced 2009 aluminum matrix composite under wet machining conditions. The results showed that microwear, chipping, cleavage, abrasive wear and chemical wear were the dominating wear patterns of SCD tools, and PCD tools mainly suffered from abrasive wear on the rake face and adhesive wear on the flank face. The local temperature increase in the workpiece material adjacent to the contact surface of SCD tool was approximately as high as 505 °C. The combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix caused the severe graphitization of SCD tool with (rake face 1 1 0-flank 1 1 0) crystal orientation. The adhesive wear on PCD tool was induced by the intermittent growth and breaking off behavior of build-up-edge. SCD tool with the crystal orientation of (rake face 1 1 0-flank 1 0 0) had the best cutting performance among the three types of tools, by which the machined surface roughness Ra was less than 49 nm after cutting for over 9 km. PCD tool had a steady and favorable cutting performance and could produce acceptable surface quality when the cutting distance was less than 6 km, during which the value of Ra was less than 46 nm and varied in the range of 12–15 nm. For this tool, adhesive wear on the rake face and abrasive wear on the flank increased gradually with the increase of cutting distance. The flank wear value of PCD was only 50 μm which was slightly higher than that of straight-nose SCD (40 μm) when cutting for 6.22 km. For all the three types of tools, with the increase of cutting distance, the machining induced defects such as craters and scratches increased too. Especially, when cutting distance was long enough to cause severe tool wear, material swelling on the machined surface was severe due to the plastic side flow. The chips formed by PCD tool were more discontinuous and fragmentary than that for straight-nose SCD tool.

Introduction

For some precision or ultra-precision applications, such as inertial guidance systems, satellite antennae/bearing, laser reflection mirror, optical benches and high speed manufacturing equipment, exceptional resistance to distortion from high thermal gradients and mechanical stresses is often required [1]. Silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al) have many outstanding properties such as high specific stiffness/strength, high wear resistance, low density, high thermal conductivity and low thermal expansion, which could wonderfully meet the requirements mentioned above [1], [2]. In the last decade, great attention has been paid to the precision/ultra-precision machining of SiCp/Al composites [3], [4], [5], [6], [7]. Due to the low plasticity and fracture toughness, non-uniformity and abrasive nature of the reinforcement, machinability of this kind of material is poor which embodied in excessive tool wear and poor surface finish even cut with diamond tools [8], [9], [10], [11]. Generally speaking, in the research of ultra-precision machining of SiCp/Al composites, most of the researchers limited their studies to the influence of cutting parameters, volume fraction and mean size of reinforcement particles on surface roughness or surface quality. Few articles have been related to the single diamond tool wear when ultra-precision turning of SiCp/Al composites. A suspected diffusive-abrasive wear of SCD tool has been found by N.P. Hung when ductile-regime machining of 10 vol.% SiCp/A359 composites was performed [5]. Unfortunately, the theoretical explanation has not been provided. Moreover, the direct experimental evidence has not been reported yet. The present study intends to enhance the understanding of the machinability of SiCp/Al composites by investigating the details of the diamond tools wear mechanisms and the applicability of SCD and PCD diamond tools when ultra-precision turning of 15 vol.% SiCp/2009Al composite.

Section snippets

Materials

The machined material in the experiments was 15 vol.% SiCp/2009Al which was produced through powder metallurgy technology and the extrusion ratio was 15:1. In particular, the mean size of the reinforcement particle was 2 μm. The 2009Al alloy contains 3.8 wt.% Cu, 1.4 wt.% Mg, 0.14 wt.% Si, 0.1 wt.% Fe and balanced Al. The typical microstructure of 15 vol.% SiCp/2009Al composite is shown in Fig. 1.

Ultra-precision turning experiments

Commercial grade natural single crystal diamond (SCD) and polycrystalline diamond (PCD) tools were

Chipping, peeling and abrasive wear

Fig. 2 shows the wearing pattern of round edge SCD tool after cutting 15 vol.% SiCp/2009Al for 6.4 km, while Fig. 3 displays the wearing pattern of straight-nose SCD tool. Obviously, microwear, chipping, abrasive wear and cleavage can be found on SCD tools. During machining SiCp/Al composites, the tool cut the soft aluminum alloy matrix and the hard reinforcement particle alternately. When encountered hard SiC particles, the cutting tool suddenly released from the state as it passed into soft Al

Conclusions

Based on the above analysis, the following conclusions can be drawn:

  • (1)

    Microwear, chipping, cleavage, abrasive wear and chemical wear were the dominating wear patterns of SCD tools, while PCD tool mainly suffered from abrasive wear on the rake face and adhesive wear on the flank face. It was the combined effects of abrasive wear of SiC particles and catalysis of copper in the 2009Al matrix that have caused the severe graphitization of SCD tool.

  • (2)

    The graphitization of SCD tool when machining SiCp

Acknowledgements

This project was supported by a grant from the State Key Laboratory Foundations of Science and Technology (51464010604HK1301) and the Institutions Natural Foundations of Jiangsu Province (09KJB460004). The authors would like to thank Liu Baoyuan and Liu Yi from Beijing Precision Engineering Institute for Aircraft Industry for their help in the experiments.

Cited by (77)

View all citing articles on Scopus
View full text