Influence of chromium content on the dry machining performance of cathodic arc evaporated TiA1N coatings

Physical vapour deposition (PVD) titanium aluminium nitride coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in a number of aggressive metal-cutting operations, namely, dry and high-speed machining. In this investigation, the performance of Ti1−xAlxN and Ti1−x−yAlxCryN coatings was assessed on Co-HSS twist drills used to machine grey cast iron. The failure criterion for drills was defined as a critical sized flank wear land at the outer corners of the drills. Using this criterion, the average tool life of uncoated twist drills was increased by factors of 2.5, 3.0 and 3.0 by Ti0.59Al0.41N, Ti0.27Al0.19Cr0.54N and Ti0.21Al0.14Cr0.65N coatings, respectively. Notwithstanding the similar increase in average tool life, the Ti1−x−yAlxCryN coatings produced more consistent results than the Ti1−xAlxN coated drills with standard deviations of 67, 3 and 19 holes, respectively. This result has significant practical implications in manufacturing, since drills are not replaced on an individual basis, but rather on a preset tool change frequency. The present paper discusses the performance of Ti1−xAlxN and Ti1−x−yAlxCryN coated drills in terms of average and practical drill life and concludes with remarks on the characterisation of PVD coatings and their significance on the performance of Co-HSS twist drills when dry machining grey cast iron.

Decision support tool for production planning of a machining line

A decision support tool for production planning was developed to perform the difficult and time consuming task of allocating resources within the industrial partner's machining line, consisting of identical Computerized Numerically Controlled machines. The production-planning tool identified significant labour savings in a number of the industrial partner's production plans.

Assessment of machining characteristics of austempered ductile iron

Austempered Ductile Iron (ADI) is a modified Spheroidal Graphite Iron (SGI) produced by applying a two-stage heat treatment cycle of austenitising and austempering. The microstructure of ADI also known as "ausferrite" consists of ferrite, austenite and graphite nodules. Machining ADI using conventional techniques is often problematic due to the microstructural phase transformation from austenite to martensite. Machining trials consisted of drilling ADI-Grades900, 1050, 1200 and 1400 using inserted (TiAlN PVD coated) type drills. The cutting parameters selected were; cutting speeds [m/min] of 30 and 40; penetration rates [mm/rev] of 0.1 and 0.2; to a constant depth of 20mm. The machining characteristics of ADI are evaluated through surface texture analysis and microhardness analysis. These results indicate that microhardness is modified during machining and surface texture is improved using a cutting fluid.

Deformation induced phase transformation during machining of Ti-5553

Ti-5553 is a relatively new titanium alloy with applications particularly in the aerospace industry for such key structural components as landing gear. However, during machining of Ti-5553, the elevated temperature and high strain at tool-workpiece interface may alter workpiece microstructure and result in ß to a phase transformation. During phase transformation, some intermediated phase such as w phase may form which is brittle and hard to machine, and it could reduce the fatigue life of machined components. The aim of this research work is to optimize the machining condition for Ti-5553, in which its hot deformation behavior in terms of ß to a phase transformation could be fully understood. Analysis of variables such as micrographs of phase components and cutting zone temperature demonstrates that the cutting temperature governs the formation of final phase components and to some extent this variation has been quantified to allow for further and more detailed investigation.

Wear characteristics of ultra-hard cutting tools when machining austempered ductile iron

Nodularised Ductile Cast Iron, when subjected to heat treatment processes - austenitising and austempering produces Austempered Ductile Iron (ADI). The microstructure of ADI also known as "ausferrite" consists of ferrite, austenite and graphite nodules. Machining ADI using conventional techniques is often a problematic issue due to the microstructural phase transformation from austenite to martensite during machining. This paper evaluates the wear characteristics of ultra hard cutting tools when machining ADI and its effect on machinability. Machining trials consist of turning ADI (ASTMGrade3) using two sets of PCBN tools with 90% and 50% CBN content and two sets of ceramics tools; Aluminium Oxide Titanium Carbide and Silicon Carbide - whisker reinforced Ceramic. The cutting parameters chosen are categorized as roughing and finishing conditions; the roughing condition comprises of constant cutting speed (425 m/min) and depth of cut (2mm) combined with variable feed rates of 0.1, 0.2, 0.3 and 0.4mm/rev. The finishing condition comprises of constant cutting speed (700 m/min) and depth of cut (0.5mm) combined with variable feed rates of 0.1, 0.2, 0.3 and 0.4mm/rev. The benchmark condition to evaluate the performance of the cutting tools was tool wear evaluation, surface texture analysis and cutting force analysis. The paper analyses thermal softening of the workpiece by the tool and its effect on the shearing mechanism under rough and finish machining conditions in term of lower cutting forces and enhanced surface texture of the machined part.