Page 18 - The Machining World Express May 2024

INSIGHT THE MACHINING WORLD EXPRESS | MAY 2024

Machinability of Ti & Ni based alloys

Superalloys are known to be hard to process machine difficult-to-machine parts with ease petrochemical, and biomedical. These highly
materials by reason of their elevated and precision. Advanced cutting tools help engineered alloys offer unique combination of
temperature resistance, fast strain hardening, optimize machinability. Because hard-to- heat resistance, corrosion resistance, toughness,
minimal thermal conductivity, and the existence machine materials need an advanced insert high operating temperature, and strength-
of abrasive deposits in the structure. At this to endure high heat creation, toughness and to-weight ratio. These alloys are termed as
point, it required the advancement of tools impact resistance in machining. Cutting tools “Difficult to machine materials” because of
(carbides, ceramics and CBN) with superior utilized in the machining of superalloys have their low machinability rating. They are difficult
thermal and chemical constancy for improving properties such as wear strength, excellent to machine because of properties like low
the machinability of aerospace alloys. Poor thermal shock, chemical consistency, high thermal conductivity, high strength at elevated
machinability of aircraft engine alloys exposes strength and toughness, efficient hot hardness temperatures, and high chemical reactivity.
the tool cutting edge to extreme thermal and at high temperatures at the cutting edge and At the same time, superalloys are a valuable
mechanical pressures and these frequently workpiece. In the machining of nickel-based class of high temperature materials used in the
cause rapid tool wear superalloys and titanium alloys, uncoated and strongest parts of jet and rocket engines where
coated sintered carbide tools and ceramic and temperatures get to 1200-1400 °C
Nickel based super alloys display rather difficult CBN tools are generally used in continuous
machinability characteristics owing to their high cutting applications at high speeds.
temperature strength, work hardening tendency
and low thermal diffusivity. Like stainless steels,
their austenitic matrix is responsible for work Super Alloys : Playing the
hardening during machining. Besides, during critical role
high machining temperatures, these alloys have
affinity to weld with the tool material. The strong Ti-Based Alloys are structural materials
tendency to form built up edge (BUE) and the widely utilized in the aviation industry. These
presence of hard intermetallic compounds and alloys are known to exhibit features such as
abrasive carbides in their microstructure further superior biocompatibility, osseointegration,
exacerbate cutting difficulties. Excessive tool high wear and corrosion strength and superior
wear is one of the major problems in machining compressive strength within the body. The
of nickel-based superalloys. Because of the low low thermal conductivity of the materials Ni-based alloys - The ability to retain
thermal conductivity, most of the heat produced causes high temperatures in the cutting region. high mechanical and chemical properties at
during machining is transferred to the tool. This temperature in the cutting region is high elevated temperatures makes superalloys an
Subsequently, high tool tip temperatures cause average. Demand for titanium is steadily excellent material for use in rotary and stationary
excessive tool wear, which can limit cutting improving in the aerospace industry, components of jet engines. Components
speeds and reduce productivity. Another and other alloy forms, from aluminum alloys, manufactured by superalloys are lighter
factor negatively affecting the machinability steels, etc. Titanium also resists corrosion than those produced from traditional steel.
is the continuous and tough chips produced factors by forming oxide in the surface layer in Approximately 50% by weight of aircraft engine
during machining. Although there are significant application environments. Titanium alloys are alloys are nickel-based alloys. These alloys
improvements in cutting tools, machine control also frequently used in airframe subjected to air- present a higher strength / weight ratio than
systems, cooling and lubrication technology, kinetic heating due to its thermal stability steel with higher density.
machining of superalloys is still leading to
problems in terms of cutting tool wear and The superalloys are an exceptional metal
surface integrity. class with a combination of high temperature
resistance, toughness and resistance to oxidizing
Being a major cause of the poor machinability environments. Nickel-based superalloys are
of the superalloys, tool wear is an inevitable commonly applied in engine parts for instance
process during machining and it progresses until engine compressor discs, turbine disc, bearing
tool life ends. However, should the precaution parts, housing, fins and other running parts.
be taken by knowing the type, rate and timing
of the wear, the negativity of the tool wear can
be minimized.

Cutting speed stands as the major factor of The quick growth in the aviation industry has
tool wear in machining of Ni-based superalloys. laid the groundwork for the development of
Tool wear rate is higher in areas in which materials used in aircraft construction. The main
concentrated force and temperature is present. factor is the reduction in weight and increased
This increased temperature negatively affects service life of aircraft components, resulting in
carbide tools, as they are composed of cobalt lower costs. Therefore, a lot of research was
binders. While in ceramic tools, feed rate done for improving materials by optimized
increase, which causes excessive flank wear, is properties to reduce weight, increase damage Article contributed by
the limiting factor. Feed rate is another limiting tolerance, fatigue and corrosion resistance. The
factor of tool wear. For carbide tools, average main purpose of the continuous development RAJESH GUPTA
to higher feed rate values is recommended. of new materials in aviation applications is VP – Sales & Marketing
For ceramic tools, lower feed rate values are to increase fuel efficiency and performance, Rudrali Hitech Tools Pvt Ltd
preferable Advances in the cutting tool industry and to reduce costs. Titanium and Nickel Experience- 30 Years
are becoming more and more promising to alloys are the most commonly used in the
demanding industries like aerospace, energy, Education- B-Tech in Mechanical,
MBA in Marketing
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