Tool-life and wear mechanisms of CBN tools in machining of Inconel 718

Abstract

The demand for increasing productivity when machining heat resistant alloys has resulted in the use of new tool materials such as cubic boron nitride (CBN) or ceramics. However, CBN tools are mostly used by the automotive industry in hard turning, and the wear of those tools is not sufficiently known in aerospace materials. In addition, the grade of these tools is not optimized for superalloys due to these being a small part of the market, although expanding (at 20% a year). So this investigation has been conducted to show which grade is optimal and what the wear mechanisms are during finishing operations of Inconel 718. It is shown that a low CBN content with a ceramic binder and small grains gives the best results. The wear mechanisms on the rake and flank faces were investigated. Through SEM observations and chemical analysis of the tested inserts, it is shown that the dominant wear mechanisms are adhesion and diffusion due to chemical affinity between elements from workpiece and insert.

Super Abrasive Machining of Integral Rotary Components Using Grinding Flank Tools

“…Nevertheless, it must be taken into account that recently other PVD coatings based on The alloy offers good resistance to fatigue and creep combined with high corrosion resistance under high temperatures [28]. Nevertheless, these properties involve high cutting forces during machining, low material removal rates, adhesions, and other issues, which enhance premature tool wear [28][29][30][31][32][33]. In the light of these concerns, selecting this material for experimental case of study implies aggressive machining conditions and becomes suitable in order to test SAM behavior and establish a comparison with conventional milling process.…”

Performance and wear mechanisms of whisker-reinforced alumina, coated and uncoated PCBN tools when high-speed turning aged Inconel 718

“…Costes et al [7], when performing EDX line scan on the fracture surface of worn PCBN tools used in turning Inconel 718, have shown presence of diffused Ni, Cr, Fe and Nb in superficial layer of the tool crater. On the other hand, Angseryd et al [27] have emphasized the need for careful sample preparation, which, if not followed, can result in considerable scatter of results.…”

“…Attempts on application of PCBN tools has been made in 1990-th but available PCBN material had high cBN content (90-95%) with metallic or ceramic (AlN, AlB 2 ) binder and the cutting speed for such tools was limited to 90-120 m/min [5]. Recent developments in the PCBN materials related to optimization of cBN content and a type of binder have led to extension of cutting speed range to 200-300 m/min for turning Inconel 718 [6,7]. Performance of PCBN tools when machining other Ni-based superalloys has also been subjected to study [8,9].…”

“…), stemmed from high cutting temperature, were found to govern the wear rate of the tools [8]. Application of ceramic binder of TiN, TiC, Ti(C,N), AlN, AlB 2 , etc., reduces the amount and exposure of cBN particles to the chemical wear [7] as well as facilitates in formation of built-up-layer which acts as a diffusion barrier [5,10]. Application of coatings on PCBN tools is expected to act as an additional diffusion barrier [11] and therefore facilitate suppression of chemical wear.…”

Self-Organization of PVD Cemented Carbide Tool When Cutting In718

“…Studies of wear of cutting tools when machining In 718 have been carried out by different researchers. Chen and Liao [7] studied the wear mechanisms in drilling of In 718 with carbide tool; Li et al, [8] studied the wear in milling of In 718 with carbide tool; Costes et al, [9] studied the wear mechanisms in turning of In 718 of CBN tools; Devillez et al [10] studied the wear in turning of In 718 with coated carbide tools. All these studies made detailed analysis of various tool failure mechanisms when cutting In 718.…”