Abstract:
This study presents an investigation of titanium nitride (TiN) coated cemented carbide K-ISO grade cutting insert wear mechanism during interrupted dry turning operation of (As-cast and ASTM 25 grade) grey cast iron workpiece. Vibration is imminent in turning operation greatly experienced between the workpiece and cutting tool thus have detrimental effect on machined part surface finishes, dimensional accuracy and cutting tool wear. Tool post vibration effect on tool wear and workpiece surface roughness were studied by obtaining a cutting parameters combination that gave better cast iron surface finishes and minimum vibration amplitude. Design of experiment were based on Taguchi L16 orthogonal array using four different level cutting parameters combinations and machining time. Experimental turning operation were carried out on conventional lathe GML-1440BGF model with ASTM 25 grade workpiece and GH-16402X model with grey cast iron (As-cast) respectively to investigate and compare their surface roughness and vibration amplitude measurement. ASPEX 3020 model Scanning Electron Microscope (SEM) was used to examine the various types of wear mechanism obtained viz; flank and crater wear, adhesion, edge chipping and abrasions mechanism observed on these used coated cutting inserts under varying cutting parameters. Surface roughness and tool post vibration amplitudes were measured under each turning trial with aid of Profilometer (SRT-6200) roughness tester and portable (X16-4 model) Accelerometer device accordingly under each turning trials. Minitab 17.0 software was used to investigate and model the relationship between the independent variable (cutting speed, feedrate and depth of cut) and responses (surface roughness and vibration amplitude). A multiple regression model equation was formulated to compare predicted with experimental results thereby established fitted model. Also Analysis of variance (ANOVA) was done to investigate which design factors and their interactions affecting the response significantly. From the experimental results a combination of highest cutting speed, lowest feedrate and depth of cut were gave better surface finishes of considered workpiece. For ASTM 25 grade, cutting parameters (Vc = 150 m/min, f=0.272 mm/rev and 0.6mm) gave finest surface finishes (Ra) 1.175μm while (Vc = 165 m/min, f=0.2 mm/rev and 0.25mm) yielded (Ra) 1.5 μm for As-cast material. Minimum tool post vibration of amplitude of 9.643 m/s2 was recorded for ASTM 25 grade and 6.214 m/s2 for As-cast under a combination of lowest cutting parameters
