High Speed Cutting Inconel 718 with Coated Carbide and Ceramic Inserts

High speed machining (HSM) technology is one of important aspects of advanced manufacturing technology. Nickel-based superalloys have been widely used in the aircraft and nuclear industry due to their exceptional thermal resistance and the ability to retain mechanical properties at elevated temperatures of service environment over 700 ℃. However, they are classified as difficult-to-cut materials due to their high shear strength, work hardening tendency, highly abrasive carbide particles in the microstructure, strong tendency to weld and form built-up edge and low thermal conductivity. They have a tendency to maintain their strength at high temperature that is generated during machining. The Inconel 718 workpiece material used in the experiment was in the hot forged and annealed condition. The commercially available inserts (all inserts were made by Kennametal Inc.) were selected for the tests, a PVD TiAlN coated carbide, a CVD/PVD TiN/TiCN/TiN coated carbide and a CVD Al 2O 3/TiC/TiCN coated carbide were used at the cutting speed range about 50～100 m/min. Three kinds Sialon grade inserts with various geometry and cutting angles were used at the cutting speed range from 100 m/min to 300 m/min. For evaluating the inserts machinability when high speed cutting Inconel 718, Taylor Formula within certain cutting speeds, an high speed cutting experiment of tool life was carried out to establish the models of tool life by means of rapid facing turning test. The conclusions drawn from the turning of Inconel 718 with silicon nitride based ceramic; PVD and CVD coated carbide inserts are as follows: Studies on tool wear in high speed machining. The thorough investigations and studies were made on the tool wear form, wear process and wear mechanism in high speed cutting of difficult-to-machine materials with ceramic tools and with coated carbides. The major wear mechanisms of nickel-based alloys are interactions of abrasive wear, adhesion wear, micro-breakout and chipping. Optimization analysis on the application of high speed machining. Based on the experimental results, the optimal cutting parameters were determined for machining of Inconel 718 at high speed. The recommendation of tool inserts for high speed cutting inconel 718 were ceramic inserts of KY2000 with negative rake angle and KY2100 with round type, the PVD coated carbide insert KC7310 was recommended for its lower price.

High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposition.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting temperature,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.