Varun Nayyar

Machinability of compacted graphite iron (CGI) and flake graphite iron (FGI) with coated carbide

Compacted graphite iron (CGI) has an important role in manufacturing of new generation engines. Better strength of CGI, as compared to flake graphite iron (FGI), allows CGI engine to perform at higher peak pressure, higher fuel efficiency and lower emission rate. However, the machinability of CGI is as poor as compared to FGI. The machinability of CGI is an area that needs to be studied in a better way to cut the production cost of the engine. It is a well known fact that the as-cast engine block has varying microstructure and mechanical properties due to different cooling rates at different locations of such a geometrically complex component. This has highlighted the need for studying machinability as a function of microstructural and mechanical properties so that the machining process could be optimised. For this reason, machinability of 18 different types of CGI materials along with two FGI materials has been studied, in terms of cutting force and tool life, in a turning operation in this work.

An experimental investigation of temperature and machinability in turning of compacted graphite irons

The life and the performance of an insert in metal cutting are mainly dependent on the heat that is generated in the contact zones on the tool rake face with chips and on the flank face with the transient and machined surfaces. According to tool life standard, the wear on the flank face is usually taken as a decision for tool life. This occurs because of contact stresses, temperature and friction between tool workpiece contacts. Hence, knowledge of temperature on the flank face becomes important. The temperature on the flank face has been measured in this work for different CGI materials having different microstructure and physical properties in a turning operation. It has been seen that there is no significant difference of flank temperature, while machining different CGI materials having hardness from (140 to 236 HBW). For temperature measurement, special inserts integrated with gold-platinum thermocouple on the flank face were used. It has been noticed that the materials having 31% resultant cutting force difference and six to eight times tool life difference have almost same temperature on the flank face measured at different distances from the edge line of the insert.

An Experimental Investigation of the Influence of Cutting Edge Geometry on the Machinability of Compacted Graphite Iron

Compacted graphite iron (CGI) is considered as the potential replacement of flake graphite iron (FGI) for the manufacturing of new generation high power diesel engines. Use of CGI, that have higher strength and stiffness as compared to FGI, allows engine to perform at higher peak pressure with higher fuel efficiency and lower emission rate. However, not only for its potential, CGI is of an area of interest in metal cutting research because of its poor machinability as compared to that of FGI. The higher strength of CGI causes a faster tool wear rate in continuous machining operation even in low cutting speed as compared to that for FGI. This study investigated the influence of cutting edge geometry at different cutting parameters on the machinability of CGI in terms of tool life, cutting force and surface roughness and integrity in internal turning operation under wet condition. It has been seen that the cutting edge radius has significant effect on tool life and cutting forces. The results can be used to select optimum cutting tool geometry for continuous machining of CGI.

Investigation of microstructure and material properties for 18 different graphitic cast iron model materials with focus on Compacted Graphite Iron (CGI)

The higher mechanical strength of Compacted Graphite Iron (CGI) than Flake Graphite Iron (FGI) makes it very useful material for several commercial components. The knowledge of microstructure and hence the mechanical properties and machinability is very important for the CGI to used efficiently in manufacturing. The complex geometry of cast components makes it difficult to produce adequate microstructure in the whole component.Adequate material properties can be achieved by having good knowledge about the correlations between the casted geometry, graphite morphology and pearlite content. In the presented paper, 18 different model materials have been analysed extensively, concerning the effect of chemical composition, solidification and cooling rate on the nodularity, pearlite content, interlamellar spacing in pearlite, hardness and mechanical properties. Later, the cutting force measurement tests were performed on some of the materials and it was found that the forces have a strong positive correlation with pearlite content and the tensile strength of the materials.