Comparison of Performance of Austrian made Si3N4 - Nitride Ceramic Tools Used to Machine Grey Cast Iron Work-piece Materials
Abstract:
This article presents comparisons of cutting performance of Austrian made – Si3N4 nitride ceramic – inserts used in machining a Type 422425 grey cast iron work-piece materials. Three commercial ceramic inserts Type FMG121C, FMG122C, and FMG134C were tested. Experiments were focused on tool life tests. A comparison approach involved exponents of Taylor’s type equations over an optimized cutting tool interval i.e. one constant depth of cut of 1mm, one constant feed rate of 0.2mm/rev and the three cutting speeds 250, 320 and 380m/min. Results were obtained from linear regression. Also conducted was an evaluation of intervals of reliability as well as corresponding standard deviations for each regression coefficient in experimental Taylor’s equations. The experiments allowed to compare, from statistical perspectives, at a 95 and greater confidence level, the trends and quantities of experimental cutting inserts. The results showed that a Type FMG122C ceramic insert had the most superior performance compared to other two types of experimental ceramic inserts investigated in this study. It is believed that this information can be useful for both tool manufactures and end users involved in machining cast iron work-piece materials and interested in improved cutting performance.
Introduction:
Generally, ceramic cutting tool inserts (CTI) are acknowledged especially for good machining performance where the exceptionally high speeds and high temperatures are of major concerns (Audy 1996). Good wear resistance due to durability of such tools improves tool life and allows for using cutting speeds up to 1000 m/min. Other advantages of the ceramic materials are their improved resistance to high temperatures up to 1750°C. According to literature source (Humar 2008) the cutting ceramics can be divided to an oxide group or a nitride group based on Al2O3 or Si3N4 components, respectively. The nitride cutting ceramics (NCC) have been found, when compared to the oxide cutting ceramics, better in terms of improved heath shock resistance. However they exhibited lower chemical stability when machining steel work piece materials.
At a department of Technical University of Liberec (Czech Republic) in machining / metrology laboratories, several graduation theses’ topics were set up to investigate and compare the cutting performance of three nitride ceramic cutting inserts of a square shape. The commercial names of the inserts were FMG121C, FMG122C and FMG134C, and they were from an Austrian Research Institute.
Consequently, the prime concern of this study was to carry out the comprehensive tool life tests. It was decided to run long-term tests to examine the life span of the cutting tool inserts. It was noted that that such tests are expensive ad time consuming (Audy 1996, 2002), however, on other hand they provide much accurate results (Audy et al 2002, and Audy 2003, Humar 2008, Beno 1999) than the short-term tests.
