th, hardness, wear resistance, nt proportions, Cr improves
rength and hardness of steel.
ess and hot hardness.
ghness and hot hardnessghness and hot hardness.
d toughness.d toughness.
wth during elevated cing strength and toughness
Carbon SteelsCarbon Steels
Hi h C b t l (0 6 t 1 5% CHigh Carbon steel (0.6 to 1.5% Car
Small percentages of silicon, mangused to help refine grain size and inused to help refine grain size and in
Easily shaped and sharpened
Greater resistance to abrasive wea
Do not have sufficient hot hardness
Widely used for files, saw blades, c
Speeds – 5 m/minSpeeds – 5 m/min
b )rbon)
ganese, chromium and vanadium are ncrease tool hardnessncrease tool hardness
ar
s (200°C) for cutting at high speeds
chisels, taps, broaches and reamers
High Speed Steel
High speed tool steel differs from plain high csteel in the addition of alloying elements to hastrengthen the steel and make it more resistastrengthen the steel and make it more resista(600 0C)
Commonly used alloying elements: many y gchromium, tungsten, vanadium, molybdeand niobium
The M series (10% Mo, with Cr, V, alloying elements) represents tool molybdenum type and the T seriesV and Cobalt as alloying elements)y g )the tungsten type.
Weq = 2 (%Mo) + %Weq ( )
Some of the High SpeedSome of the High Speedpowdered metal (PM) fo
carbonarden and ant to heatant to heat
nganese,g ,enum, cobalt
W and Cobalt as steels of the
s (18% W, 4% Cr, 1% ) represents those of ) p
d Steels are now available in ad Steels are now available in aorm.
Cast Cobalt AlloysCast Cobalt Alloys
A typical composition for this cla21% W, and 2% C which gives a
Cast alloys provide high abrasiofor cutting scaly materials
They are not as tough as HSS acutting operations.
When applying cast alloy tools, tmind and sufficient support shou
Speeds – 45 to 60 m/min.
ss of tool material was 45% Co, a hot hardness of 750 °C)
n resistance and are thus useful
and are sensitive for interrupted
their brittleness should be kept in uld be provided at all times.
CarbidesCarbides
Also known as cement
Because of their high hardness (thermal conductivity, abrasive recarbides are the most importantp
and die materials for a w
Most carbide tools in use todayMost carbide tools in use todaycarbides of W-Ti or W-Ti-Ta, de
be ma
Speeds –
ted or sintered carbides
(1000 °C), High elastic modulus, esistance and chemical stability, t, versatile and cost effective tool ,
wide range of applications
y are either straight WC or multiy are either straight WC or multiepending on the work material to chined.
125 m/min.
Cemented Carbide
FIGURE: P/M process for making ce
e Inserts
emented carbide insert tools.
Production of WCProduction of WC
Blended WC powder produced byBlended WC powder, produced bymixing WC (94%) with Cobalt (6%)
in a ball milling press
Carbide blending equipment, Ball mill
Production of WCProduction of WC
Blended WC powder is then dried and pcompacted using a pill press
The compacted powder is then sintered in p pa sintering furnace at 1350 to 1600 °C
CarbideCarbide
Typical carbide inserts withfeatures; round ins
The holes in the inserts are stThe holes in the inserts are st
InsertsInserts
various shapes and chip breakerserts are also available.tandardi ed for interchangeabilitytandardized for interchangeability.
Methods of attachingMethods of attaching
(a) Clamping, and
(c) threadless lockpins (d) In
inserts to toll holdersinserts to toll holders
(b) Wing lockpins
sert brazed on a tool shank
Boring Head
FIGURE: Boring head with carbide insert cuttincause the chips to curl tightly and br
ng tools. These inserts have a chip groove that can reak into small, easily disposed lengths.
Insert StrengthInsert Strength
FIGURE: Relative edge strength and tendency forchipping and breaking of inserts with various shapeschipping and breaking of inserts with various shapes.Strength refers to that of the cutting edge shown by theincluded angles. Source: Courtesy of Kennametal, Inc.
FsFIGURE: Edge preparations for inserts to improve edgestrength. Source: Courtesy of Kennametal, Inc.
Coated Carbide To
Necessity: New alloys and enstrength and toughness Thesestrength and toughness. These
chemically reac
Need for improving the performaNeed for improving the performamaterials has led to import
Coated tools don’t perform
The thickness of these coa
Speeds –
ools
ngineered materials, which have high e materials are generally abrasive ande materials are generally abrasive andctive with tool materials.
ance in machining common engineeringance in machining common engineeringtant developments in coated tools.
m efficiently at low cutting speeds.
atings is on the order of 2 to 10 µm.
200 to 250 m/min.
Coating MaterialsCoating Materials
CTitanium Nitride:
(Gold Color)
Titanium Carb
(Gray Color
Low friction ffi i t
Theseticoefficients,
highhardness,
i t t
coatingsWC insehave higfl kresistance to
hightemperature
d d
flank weresistan
inhi iand good
adhesion to the substrate.
machininabrasivmaterial
bide:
r)
Ceramics:(Black Color)
e High chemical inertness lowon
ertsgh
inertness, lowthermal
conductivity, high thermal stabilityear
ce
thermal stability,resistance to flank and crater wear. However ceramicng
vels.
However ceramiccoatings bond weakly to the
substratesubstrate.
Cutting inserts indicating the diverse range of shapes
Coating Materialsg
Diamond Coatings:
Effective in machining abrasive materials
Tool life will be improved by ten f ld h d t thfolds when compared to other
coated tools.
Poor adherence characteristics and difference in thermal
expansion between diamond and substrate materialsand substrate materials.
