Abstract
The research paper presents the tribological aspects of cutting tool wear during the turning of stainless steels. An experiment was conducted in order to assess the wear of carbide cutting inserts with CVD-applied anti-wear coatings (CNMG 12 04 08 ZSZ and CNMA 12 04 12-KR 3205) and an uncoated ceramic cutting insert (CNGA 12 04 08 T0102 WG 650). The test subject included the following stainless steel grades X20Cr13 (1.4021) and X8CrNiS18-9 (1.4305). The analysis involved the direct wear indicator, VBBmax, and the indirect wear indicator, which was the roughness of machined surfaces and the Ra parameter. Based on the obtained results for both X20Cr13 and X8CrNiS18-9 steels, it was noticed that the best durability was exhibited by the CNMG 12 04 08 ZSZ insert, whereas the worst durability was identified for the CNGA 12 04 08 T0102 WG 650 insert. When analysing the results obtained with the VBBmax direct indicator, it was observed that in the case of each of the insert, most often the course of their wear was of nature similar to linear. Comparing the VBBmax direct indicator with the indirect indicator, namely, the measured Ra parameter, it was concluded that they were convergent. Upon the deterioration of the surface quality, greater values of the selected geometric measure of wear on the flank face were also identified.
Highlights
A cutting tool and a machined workpiece constitute a specific type of a tribological pair.The conditions prevailing within a cutting zone are characterized by high mechanical and thermal loads present at the contact point of the tool with the workpiece and chip, as well as high speeds between individual elements of the tribological pairs [1,2]
It is related to visible deterioration of surface quality at the moment of increasing the value of the selected wear indicator VBBmax ; During machining of both the X20Cr13, as well as the X8CrNiS18-9 steels, a step-wise increase of surface roughness upon the appearance of significant cutting edge wear was noted; The worst surface quality was obtained after turning with the CNGA 12 04 08 T0102 WG 650 insert, while the best surface quality was obtained after the CNMG 12 04 08 ZSZ insert; The differences in the obtained values of the VBBmax wear indicator and the surface roughness
Ra result from the dissimilar wear mechanisms of CNMG 12 04 08 ZSZ compared to the other two inserts; Cutting edge wear for CNMG 12 04 08 ZSZ insert was abrasive, and chipping eventually appeared
Summary
A cutting tool and a machined workpiece constitute a specific type of a tribological pair.The conditions prevailing within a cutting zone are characterized by high mechanical and thermal loads present at the contact point of the tool with the workpiece and chip, as well as high speeds between individual elements of the tribological pairs [1,2]. A cutting tool wear may be of mechanical (abrasive, strength-related, and plastic deformation), adhesive, chemical (diffusion, oxidation), and thermal nature [3,4,5,6,7,8,9]. It is most commonly associated with geometrical changes and varying physical properties of the tool under operation. The geometrical changes are caused by the friction that is related to loss of edge material, whereas the changing properties by local plastic deformation, high temperatures, and the chemical impact of the cooperating medium.
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