Cermets

 

 

Ceramic (Cermet) Saw Tips - What They Are:

TiCN is harder and slicker than Tungsten carbide. It is more corrosion and wear resistant with higher lubricity than carbide.  This is one of the new generation ceramics developed for jet turbines, for steel cutting tools and armor on an Abrams M-1 tank.  Refer to our Carbide and Advanced Materials Index for more articles with information on carbide and ceramics.

 

Titanium Carbonitride has been used as a coating on carbide tools since the 50’s.  It has been tried on saws for years but no one could keep the tips on.  U.S. patent 6,322,871 fixed that problem.  

 

Cermet saw tips are TiCN (Titanium Carbonitride).   The Cermets are composed entirely of TiC (Titanium Carbide) and TiN (Titanium Nitride).  These are the same materials used to coat ordinary grades of carbide to make them more wear resistant.  A cermet is not coated instead it is solid coating material.  Although the US Patent Office accepts this as a ceramic it is best here to consider it as an intermediate grade between tungsten carbide and pure ceramics.  It has a lot of the good qualities of true ceramics as well as an acceptable transverse rupture strength of over 200,000 psi.

 

History: Cermets have been proven for decades in metal machining.   Cermets were tried in saws about ten years ago and did not work well.  The problem then was that they could not be brazed so they were clamped.  Cermets now work well in saws for three reasons. 1. They can be successfully brazed.  2.  The cermets are much better quality than they were ten years ago.  3.  Advances in braze alloys, such as High Impact alloys, greatly increase fracture resistance.

 

World Directory and Handbook of Hardmetals and Hard Materials - sixth Edition

Kenneth J A Brookes

Published by:

International Tungsten carbide Data

33 Oakhurst Avenue

East Barnet Hertfordshire

EN4 8DN United Kingdom

Telephone & Fax international  (+44) 181-368-4997

 

Carbonitrides

Though they largely originated in the United States, the growing popularity of carbonitride hardmetals is very much due to technical developments and semi-political pressures in Japan. These influences encouraged companies to make and use hardmetals based on titanium rather than 'strategic' tungsten (of which the main source was and is mainland China) and technical development replaced the more brittle carbide-based materials with tougher Carbonitrides.   Oddly, the first carbonitride material - tungsten- titanium carbonitride - was almost certainly made inadvertently during the late 1940s and 1950s, when the shortage and expense of pure hydrogen caused a number of companies to employ 'cracked ammonia' (a mixture of hydrogen and nitrogen) as a substitute furnace atmosphere.

Compositions of carbonitride cermets for cutting tools are in general much more complicated than those of sintered carbides, and contain carbides, nitrides and/or carbonitrides of titanium, tantalum, niobium, tungsten. molybdenum and vanadium, with binders varying from nickel     to     complex     alloys     simulating precipitation-hardened stainless steels.

 

Cermet Properties

Cermets are one of the best kept secrets in the cutting tool industry. They provide the user with increased productivity and profitability through higher cutting speeds and extended tool life. Cermets bridge the gap between ceramics and carbides with speeds ranging from (300 -1200 s.f.m.).They also provide excellent chip control with molded or ground chipbreakers.

 

Technically, cermets are ceramic particles bonded with metal — "cer" for ceramic and "met" for metal. They are solid compositions of titanium carbide (TiC) and/or titanium nitride (TiN). More recent tungsten carbides usually have (TiC and TiN) coatings to improve tool life and resist built-up edge. After this thin coating wears away then the insert's usefulness ends. In contrast, since a cermet is a solid composition of (TiC) and/or (TiN), wear is much more gradual — thus the advantage of having a solid substrate.

 

Features of Cermets:

• Longer run life - up to 20 x carbide
• Faster feeds and speeds - greater productivity
• Better surface finishes
• More resistant to heat and chemical attack
• Reduced energy use
• Quieter, cleaner, feed smoother and stay cooler
• Cermets are very tough at cutting temperatures
• More economical - more throughput, faster speeds & longer tool life.  

 

 Making Cermet tipped tools

Brazed Cermet Tools can be made with the same equipment and techniques that are used to make carbide tipped tools.  Once the tips are treated they braze the same way carbide does.  Because cermets are more wear resistant than carbide they need different wheels and take a bit longer to grind.  Carbide Processors will supply ready to braze cermets or will treat the customer’s cermets.   Cermet tips cost about 50% to 100% more than carbide.  Treating will add about 2% to 3% to the cost of the tool. 

 

Overall the major cost increases are the costs of the tips and the increased grinding time.  This adds 20% to 30% of the cost of the total tool.  Other than that the costs are identical with carbide. Typically cermet tipped tools cost 20% more to make than carbide and sell for 50% to 100% more than carbide.

 

We developed the brazing technology and we have patent protection on essential technologies for brazed ceramic tools.  We would like to license this technology.  In the mean time we are selling saw tips and helping our customers sell saws to prove that the technology works and works very well.   We would be happy to work with anyone interested. 

 

Method of treating ceramics for use as tips in saws and other tools or other structures

United States Patent      6,322,871   Walz, et al. November 27, 2001

 

Abstract

A method of processing a ceramic body, such as a saw tip so that the ceramic body can be bonded to a substrate, such as a saw blade. The ceramic body is desirably a cermet, and it is first cleaned, preferably using sodium hydroxide. After this, the ceramic body is etched by an acid, after which a metallic coating is applied to the bonding surface either by electrolysis by an electroless process. Then the ceramic body is brazed.              

 

Fracture Toughness

Cermets are best used in semi-finishing and finishing applications. Cermets do not bend - carbides do. Roughing through scaled surfaces is usually best performed by carbides. Cermets can machine parts with interruptions but care must be taken in the form of larger lead angles, stronger insert geometries and larger nose radii. Do not rough any material using a 55° or 35° diamond cermet insert.

 

Transverse Rupture Strengths for Cermets & Tungsten Carbide  

Carbide       N/mmsq.  Cermets Mfg. Grade N/mm sq.    OM3 1,855     AB Sandvik Coromant  CT520  1,800 OM2   2,061  Newcomer   NM3   1,860    2M2    2,198 Valenite Inc  630 1,930  OM1  2,473  Bohlerit  BC725    2,050    1M20  2,611  Newcomer    NM5  2,070    3M12    2,611 Toyo Kohan Co Ltd  KN30 2,100   1M14  2,748  Hard Metal Com  HMC50  2,200    2M13  2,748     Nihon Hardmetal  NN30  2,250 1M13   2,748  Widia GmbH TT115  2,300   2M12  2,748  Dijet     CX90    2,400 1M12  2,748  Toyo Kohan Co Ltd  KN40   2,500

 

Some Hardness Values For Cermets & Tungsten Carbide

 

Carbide  Hardness  Density   Cermets  Hardness      Density Grade    Grain Size    Rockwell A      gms/cc.       Grade    HRA     g/cm. 1M20     Medium        84.5    13.55    Toyo Kohan Co     KN40     88.5       6.5 2M15     Coarse  87.3   14.15     Toyo Kohan Co     KN30  90.5       6.4 1M14     Medium   88   14.25  Nihon Hardmetal   NN30   91.5      7.3 3M12     Extra Coarse   88    14.45  Dijet Industrial      CX90  91.6      6.9 2M13     Coarse    87.7    14.35   Clarkson GmbH    30N  92     7 1M13     Medium      88.5    14.35   NTK    C50   92     7.9 2M12     Coarse     88.5     14.5    NTK    T15  92.5   6.3 3M2      Extra Coarse   88.8    14.9    Nippon Tungsten   DUX30  92.5       6.9 1M12     Medium   89.5    14.5    Duracarb BV     DC680   92.8   5.65 OM1   Medium   90   14.65  Newcomer   NM3    92.9   6.1 2M2    Coarse  90    14.95    Valenite Inc   630  93   7 1M2    Medium    91    14.95     Dijet Industrial    LN10    93.3       7.2 OM2     Fine   91.7    14.95   Toshiba Tungaloy   N302  93.5       6.4 OM3   Fine   92.2    15.05    Valenite Inc   671  93.5  7.1         Kennametal Inc      KT150   94    6.2         Delfer SRL    GD25     99    7

High Speed Capability

Depending upon the cermet grade used, speeds can range from (300-1200) s.f.m. Because of the high hardness characteristic of cermets, they are able to run at higher speeds than carbides and for longer periods of time.

 

Cermet speeds compared to carbide:

 

Material	Hardness	If you run Carbide at	Then you run Cermet at	% faster
Steel	90	450	700	155.56%
Carbon steel	100-150	600	1100	183.33%
Alloy steels	325-375	200	550	275.00%

                            

 

Surface Speed - sfm

Material	Grade	Finishing	Roughing	General Purpose
Uncoated Carbide	K313	650 - 2,200	650 - 2,000	1,600
Carbide TiN Coated	KC730	200 - 3,000	700 - 2,600	1,800
Cermet	KT125	900 – 2,600	700 - 2,300	1,600
Polycrystalline Diamond	KD100	1,000-10,000		2,500

                                         

 

Improved Surface Finish

Cermets have superior resistance to built-up edge. Less affinity with the workpiece results in superior micro-finishes.

 

Cermets are more wear resistant than carbide

 Flank wear in Carbide and Cermet

  

 

Cermets are Tough

Drilling concrete with a cermet tipped drill

 

Carbide is tougher than cermets or ceramics at room temperature.  The problem is that carbide gets very hot (1500F) as it cuts.  As carbide get hot is loses its rupture strength rapidly.   Cermets also lose strength as they get hot but cermets do not lose strength as fast as carbide and cermets just do not get nearly as hot. 

 

Rupture	If cermets heated up		Cermets stay cool & strong
Strength (kgf/mm2)	@ 800 C, Tungsten Carbide & Cermets are		@ 800 C Cermets are maybe 40 points stronger
200     150     100		Carbide     Cermet
Temperature Degrees C Degrees F	200   400   600    800   1000   400   750   1100  1500  1800		200   400   600    800   1000   400   750   1100  1500  1800

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