52
A. K. Choudhary and R. Jain
2.3.3.2 PcBN Tools
PcBN is a ceramic-based tool used for the welding of several hard materials and alloys
ranging from structural steels, titanium and nickel-based alloys. PcBN retains a high
hardness and strength at a higher temperature. Also, PcBN results in a good quality
weld with high weld efficiency with reduced distortion. The manufacturing of this tool
is difficult because of its low machinability. Diamond-coated tool insert is generally
preferred for machining of PcBN. In general, the cost of the tool manufactured by
PcBN is very high. It is also prone to fail during the initial phase of plunging because
of low fracture strength.
2.3.3.3 Tungsten-Based Tools
Tungsten-based tools are strong at elevated temperatures and retain their high hardness. Due to which it leads to higher wear resistance during service condition. These
tools are used for steel and titanium alloy. The titanium-based combat vehicle structures for the defense industry and circumferential segments of steel pipes were
successfully welded in a single pass of FSW without disruption with negligible
tool degradation [42]. Tungsten alloys, i.e., WC, WRe, and WC-Co are the most
promising tool materials because of high-temperature strength, fracture toughness.
The crack resistance and wear resistance of this alloy can be improved by adding a
definite amount of Rhenium. The commercially available Re based FSW tools are
W25%Re, W20%Re and W25%Re-4%HfC [43].
2.3.4 Tool Rotational Speed and Welding Speed
Tool rotation and welding speed are other crucial input parameters in FSW. Productivity and weld quality depends on how fast the tool rotates and drives off the viscous
material to create a joint. Establishing a relationship among them is slightly complicated as both are interrelated with each other. An increase in rotational speed and
reduction in welding speed leads to higher frictional heat between the tool and workpiece resulting in faster softening of the workpiece. The former increases the relative
velocity at the interface and in the case of the latter, higher contact time at the interface
leads to increase peak temperature.
Elangovan and Balasubramanian [44] studied the effect of rotational speed for
different output parameters. Rotational speed was varied from 1500, 1600, and
1700 rpm at a welding speed of 46 mm/min. They obtained a gradual decrease
in axial force and spindle torque due to an increase in developed heat. In addition,
higher rotational speed leads to more stirring of deformed material resulting in the
formation of surface defects. Elangovan and Balasubramanian [45] studied the effect
of the welding speed by varying it from 22 to 75 mm/min at a rotational speed of
1600 rpm. An increasing trend in axial force and spindle torque has been observed.
A. K. Choudhary and R. Jain
2.3.3.2 PcBN Tools
PcBN is a ceramic-based tool used for the welding of several hard materials and alloys
ranging from structural steels, titanium and nickel-based alloys. PcBN retains a high
hardness and strength at a higher temperature. Also, PcBN results in a good quality
weld with high weld efficiency with reduced distortion. The manufacturing of this tool
is difficult because of its low machinability. Diamond-coated tool insert is generally
preferred for machining of PcBN. In general, the cost of the tool manufactured by
PcBN is very high. It is also prone to fail during the initial phase of plunging because
of low fracture strength.
2.3.3.3 Tungsten-Based Tools
Tungsten-based tools are strong at elevated temperatures and retain their high hardness. Due to which it leads to higher wear resistance during service condition. These
tools are used for steel and titanium alloy. The titanium-based combat vehicle structures for the defense industry and circumferential segments of steel pipes were
successfully welded in a single pass of FSW without disruption with negligible
tool degradation [42]. Tungsten alloys, i.e., WC, WRe, and WC-Co are the most
promising tool materials because of high-temperature strength, fracture toughness.
The crack resistance and wear resistance of this alloy can be improved by adding a
definite amount of Rhenium. The commercially available Re based FSW tools are
W25%Re, W20%Re and W25%Re-4%HfC [43].
2.3.4 Tool Rotational Speed and Welding Speed
Tool rotation and welding speed are other crucial input parameters in FSW. Productivity and weld quality depends on how fast the tool rotates and drives off the viscous
material to create a joint. Establishing a relationship among them is slightly complicated as both are interrelated with each other. An increase in rotational speed and
reduction in welding speed leads to higher frictional heat between the tool and workpiece resulting in faster softening of the workpiece. The former increases the relative
velocity at the interface and in the case of the latter, higher contact time at the interface
leads to increase peak temperature.
Elangovan and Balasubramanian [44] studied the effect of rotational speed for
different output parameters. Rotational speed was varied from 1500, 1600, and
1700 rpm at a welding speed of 46 mm/min. They obtained a gradual decrease
in axial force and spindle torque due to an increase in developed heat. In addition,
higher rotational speed leads to more stirring of deformed material resulting in the
formation of surface defects. Elangovan and Balasubramanian [45] studied the effect
of the welding speed by varying it from 22 to 75 mm/min at a rotational speed of
1600 rpm. An increasing trend in axial force and spindle torque has been observed.