Engineering - Cutting Tool Study

Bearing, gear & cutter life extended by 200 - 500%.

Investigation of tribological properties of hard coatings for cutting tools

• B.P. Bandyopadhyay, U. North Dakota, Grand Forks ND
• E. Fabiszak, Micro Surface Corp, Morris IL
• GR Fenske & FA Nichols, Materials & Components Technical Division
• Argonne National Laboratory, Argonne IL

ABSTRACT

Manufacturing firms are constantly striving to improve product quality and productivity while reducing costs. proper selection of cutting-tool materials can greatly improve the productivity and quality of metal products. Hard wear-resistant coatings such as titanium carbide( TiC) and titanium nitride (TiN) applied to carbide and high-speed-steel (HSS) tool inserts are widely used in the metal-cutting industry. Recent studies have shown that premature failure of these coatings at high metal-removal rates is due to softening of the substrate.

It is believed that coating lifetime could be increased significantly by reducing the frictional heating in the tool insert. This has led to the concept of applying a thin layer of tungsten disulphide (WS2) as solid lubricant on top of TiN-coated inserts to reduce frictional heating and increase tool life. A systematic study was conducted to evaluate the performance of tool inserts with different wear-resistant coatings. Approximately 100 each of HSS and carbide tool inserts that were (1) uncoated, (2) coated with WS2 only, (3)coated with TiN only, and (4)coated with TiN and then with WS2.

The experiments were done on a numerically controlled lathe capable of continuously varying the spindle speed. During the turning operations , the three components of cutting force were monitored with a strain gauge dynamometer. Flank, notch, and crater wear were measured ate regular intervals by an optical microscope. Prior to the experiment, each coated insert was examined optically to ensure proper coatings had been applied to the rake and flank surfaces.

No cutting fluid was used in the experiments. Inserts coated in WS2 were found to have significantly lower flank wear than other inserts than inserts not coated with WS2. Application of WS2 reduced the flank notch wear of uncoated and TiN-coated inserts, with the largest reductions being observed for inserts coated with TiN and WS2. However, if tool life is defined as cutting time until the insert failed catastrophically, then TiN-coated inserts (no WS2) had the best lifetime performance. Details of the results are presented in the paper.

This paper was presented at the Japan International Tribology Conference Nagoya, Japan, October 29-November 1, 1990