Effect of mechanical pre-treatments in the behaviour of nanostructured PVD-coated tools in turning

Abstract

As a consequence of the lack of characterization of advanced physical vapour deposition (PVD) coatings in the scope of turning, a methodology is presented to evaluate the performance of nanostructured coated tools in the scope of difficult to machine materials turning in particular are austenitic stainless steels. A main aspect of this research is the evaluation of different mechanical pre-treatments before PVD coating in cutting tools. In a first stage, four advanced PVD coatings were analyzed prior to studying the effect of pre-treatments. This stage allowed to identify the nanostructured AlTiSiN coating, commercial denomination nACo, as the one with the best performance for turning austenitic stainless steel. Once the best coating is identified in a second stage, the influence of drag-grinding and microblasting mechanical substrate pre-treatments was analyzed with regard to the performance of coated tools. Several aspects were considered: geometric modification of cutting edge, coating adhesion, substrate roughness and machining performance. The performance of the mentioned coatings was evaluated through wear tests. The machined material was AISI 304L and machining operation was cylindrical turning. Each test started up using a new edge. Results showed that drag-grinding pre-treatment leads to improved coating adhesion and, therefore, in the performance of the tool. Therefore, combination of nACo coating with drag-grinding pre-treatment offers a good solution for difficult to machine metals.