ACTA TECHNICA CORVINIENSIS - Bulletin of Engineering

1.JIŘÍ ČUBAN, 2. JAROSLAV KOVALČÍKCOMPARISON OF CUTTING TOOLS INSERTSMADE OF COATED CARBIDE USEDIN TURNING OF GREY CAST IRONAbstract:This article presents comparisons of coated carbide cutting tool inserts used in machining of cylinderliners made of grey cast iron. The comparison has been realized through the tool life tests. Themeasurement has been carried out at three cutting speeds at constant cutting conditions. From theobtained values, the regression coefficients have been evaluated. Subsequently, extrapolation hasbeen carried out by means of the regression line for the cutting speed in the range of 250 – 500m/min, and for this the extended cutting speed range the interval reliability has been evaluated.Keywords:metal machining, coated carbides, cutting tool inserts, tool life tests, Taylor’s equationINTRODUCTIONCarbides are the most prevalent tool materials,they are tough and they can be used formachining using high feed rate speed, and fordifficult intermittent machining.Coated carbides consist of a hard carbide baseand coating, which increases the thermochemicalstability (carbides, nitrides, oxides andtheir combinations). As a result we get highqualitymaterials for a high rate of materialremoval and intermittent machining.The basic carbides for production of commontypes of carbides for machining are tungstencarbide (WC) and titanium carbide (TiC), thebonding metal is cobalt (Co). As the othercompounds the following are the most used:tantalum carbide (TaC), niobium carbide (NiC)and chromium carbide (Cr 3 C 2 ). Uncoatedcarbides are divided into three groups: K-grade,P-grade and M-grade. According to the ISOstandards, K-grade is a category that includescarbide cutting tools best suited for machiningcast irons and nonferrous metals and alloys; M-grade is a category that includes carbide cuttingtools best suited for machining ductile irons,harder steels, stainless steels, and hightemperaturealloys; P-grade is a category thatincludes carbide cutting tools best suited formachining a variety of steels. Coated carbidesare produced in the following way: the basemade from common carbide (K-grade, M-grade,or P-grade) is coated with a material with highhardness and excellent abrasion resistance.In the laboratories of the Department ofMachining and Assembly, Faculty of MechanicalEngineering, Technical University of Liberec,within various diploma thesis two types of thecoated carbide inserts (CCI) have beencompared. Both CCIs, type CNMA 12 04 08 AC300G and CNMA 12 04 08 AC 700G (thereinafterAC 300G, AC 700G), were manufactured by theSumitomo Electric Company. Through the longtimetool life tests the flank wear of the CCI havebeen evaluated.© copyright FACULTY of ENGINEERING – HUNEDOARA, ROMANIA 75