Abstract
In recent years, coated cemented carbides have often been the first choice for a wide variety of tool inserts and applications. Its success as a cutting tool material arises from the unique combination of wear resistance and toughness, and its ability to be formed into complex shapes. The structure obtained by sintering nanoparticle powders provides a significant improvement in product properties, such as higher cutting speeds, lower tool tolerances, and longer service life. In this study, a multi-layered gradient coating, deposited on nanostructured cemented carbides by plasma-assisted chemical vapor deposition (PACVD) was investigated with emphasis on its wear and exploitation properties. TiBN coating was deposited on nanostructured cemented carbide samples with the addition of 5 wt% Co, 10 wt% Co and 15 wt% Co. The samples were consolidated by one cycle hot isostatic pressing (HIP) technique. Complex architecture built of TiN and TiB2 gradient multilayer sequence block was deposited on each type of substrate. Wear resistance of the obtained samples was determined by erosion wear testing and dry sliding wear testing (ball-on-flat test). The friction coefficients of ~0.22 obtained for coated samples by the ball-on-flat test show a decrease in friction when compared to uncoated samples values of ~0.32. The absence of coating rupture was confirmed by wear track depth measurements showing a wear trace depth of ~1.2 μm. Exploitation properties i.e., tool life determination of samples was obtained using single-point turning tool test and compared to commercial cutting tool insert type K10 tested under the same conditions. All the conducted tests show excellent wear and exploitation properties of the newly developed TiBN coating under chosen conditions, including cutting speed, vc = 200 m/min, depth of cut, ap = 1 mm, and feed, fn = 0.2 mm. Coated WC-Co samples with 15 wt% Co, having withstood 15 min of machining with flank wear trace size less than 0.3 mm, suggest significant improvement when compared to trace size of 0.56 mm obtained for K10 commercial cutting insert.
Highlights
The development of new cutting tool materials with superior characteristics and performance, including prolonged tool service life, higher cutting speeds and loads, and lower production costs is one of the most researched areas of cemented carbides application.Tooling cost is derived by the initial material and energy input, and strongly depends on cycle time, i.e., cutting tool replacement time [1]
One of the main issues concerning coated tool materials is achieving proper adhesion between substrate and coating since it has shown to have a major impact on the cutting tool wear resistance and its service lifetime [2,3,4]
cobalt powder (Co) binder used during sintering has been shown to promote the toughness of the tool material, but at the same time reduces coating adhesion [6,7]
Summary
The development of new cutting tool materials with superior characteristics and performance, including prolonged tool service life, higher cutting speeds and loads, and lower production costs is one of the most researched areas of cemented carbides application.Tooling cost is derived by the initial material and energy input, and strongly depends on cycle time, i.e., cutting tool replacement time [1]. Coated tools have been shown to meet the high demands of different cutting processes. Cemented carbides are currently one of the major representatives of cutting tools materials for machining different metallic alloys [2]. One of the main issues concerning coated tool materials is achieving proper adhesion between substrate and coating since it has shown to have a major impact on the cutting tool wear resistance and its service lifetime [2,3,4]. The content of cemented carbide binder is another critical factor influencing wear and exploitation characteristics of the tool material. Co binder used during sintering has been shown to promote the toughness of the tool material, but at the same time reduces coating adhesion [6,7]. To minimize the negative impact of Co binder on coating adhesion, chemical etching and other types of surface treatments before coating, are often applied [8]
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