Influence of the tribological properties of the Zr,Hf-(Zr,Hf)N-(Zr,Me,Hf,Al) N coatings (where Me is Mo, Ti, or Cr) with a nanostructured wear-resistant layer on their wear pattern during turning of steel

Abstract

An increase in the speed of cutting and, accordingly, the temperature in the zone of cutting predetermines the need to develop wear-resistant coatings, functioning effectively under such operation conditions. One of the key functions of the coating is the creation of optimal tribological conditions under the influence of temperatures and force factors of the operation of the coating. The coatings of Zr,Hf-(Zr,Hf)N-(Zr,Me,Hf,Al)N (Me is Mo, Ti, or Cr) with nanostructured wear-resistant layer were studied. At temperatures up to 700 ◦C, the minimum adhesive component fadh of the friction coefficient was exhibited by a coating containing chromium (Cr), and at tem- peratures above 700 ◦C – by a coating containing molybdenum (Mo). At the turning of steel, the highest resis- tance to wear at the speed of cutting of vc = 250 m/min was exhibited by a tool with a Cr-containing coating, and at the speed of cutting of vc = 400 m/min – by a tool with a Mo-containing coating. Thus, the optimal composition of the coating depends on the speed of cutting. Information about the adhesive component fadh of the coefficient of friction makes it possible to fairly reliably predict the wear rate of the tool during cutting under the conditions of the temperatures corresponding to the temperatures at which the value of fadh was measured. It has been found that an oxide layer with a complex structure is formed in the areas of the coatings adjacent to a wear crater. Iron (Fe) and its oxide dominate in the outer regions of this oxide layer, a high content of aluminum (Al) oxide is detected in the intermediate region, and oxides of zirconium (Zr), titanium (Ti), chro- mium (Cr), and hafnium (Hf) dominate in the inner region