By value, the most important sector of the powder metallurgy industry is hardmetals, or cemented carbides. By almost any criterion, whether by volume, value or perhaps even employment, the most important hardmetal products are metalcutting tools and tool inserts. And in this area, carbide-based hardmetals are complemented by carbonitrides, sintered ceramics, superhard synthetic diamond and cubic boron nitride, and by PM tool steels.
Powder metallurgists have a triple, even quadruple or quintuple, interest in the exhibits of shows such as the International Manufacturing Technology Show in Chicago, USA: in new compositions and microstructures of cutting-tool materials; in the increasingly complex shapes of tools and inserts made by PM techniques; in wear-resistant tools for machining presintered pressings and sintered parts; in coating technologies for performance enhancement; and even, as in IMTS 2008, improved techniques for quality control of hardmetal rods and extrusions.
Regrettably, most of the sales and marketing literature distributed at exhibitions, including press releases, tend to give performance data in the form of percentage increases over “competitor” (never specified) or “previous” (whatever that was). In some cases I've included such terminology, though with many superlatives omitted, but must warn the reader against accepting such claims at face value. On occasions the statements are completely genuine, but sometimes improved performance is at the expense of reduced safety margins and results in increased danger of breakages. Sometimes the “competitor” or “previous” tool was ill-chosen or has itself been superseded. And there are all kinds of other provisos and considerations that would be taken into account had more information been available. No wonder companies are so reluctant to provide it.
Unlike some other parts of the powder metallurgy industry, many tooling manufacturers tend to save their new developments for EMO, the world machine tool exhibition (Exposition Mondiale d'Outils) held in Europe in odd-numbered years, and then to feature or relaunch them at their own national tool shows in intermediate years like 2008. Thus many items introduced or featured for the US market at the 2008 IMTS, had already been covered in my extensive review of EMO 2007 in the March 2008 issue of Metal Powder Report, pp17-23. As far as possible, this IMTS survey is of genuinely new tools and materials, gives new information or describes significant products not previously covered. For convenience, I've listed them by manufacturer.
ATI Stellram
Metal removal rates up 90%
The newly introduced 7792VX face mill takes shallow depths of cut (up to 2.4mm) and operates at high feed rates of around 3mm. Metal removal rates are improved by as much as 90% when compared to results produced with conventional cutters. In addition to high feed face milling, the 7792VX family is capable of pocketing, slotting, and plunging. The series includes smaller diameter cutters, in cylindrical shanks and modular heads, using 6mm inserts with four cutting edges.
Cutting forces are directed axially into the spindle, lessening spindle wear and improving stability. Both modern and older equipment can benefit from the adoption of this technology.
ATI Stellram's insert grade X400, with cobalt/ruthenium binder, is standard with this tooling range, and the company's choice for machining hardened steel.
Superalloy turning
4E turning geometry was designed for machining aerospace components, manufactured from high-nickel, high-cobalt and titanium-based alloys. It's complemented by a new hardmetal grade SP0819 with improved heat and wear resistance, combining micrograin substrate with “nano” TiAIN PVD coating. A reinforced chipbreaker with positive cutting action reduces built-up edge, improving surface finish and dimensional accuracy.
Guhring
Solid carbide high-performance reamers
Fifty years ago, Ed Trent and others showed that the main purpose of cutting fluid was to clear hot swarf and protect the machine, workpiece and operator, and that its action purely as a coolant tended to strengthen the workpiece and diminish — rather than enhance — productivity and tool life, especially when machining at high speeds with advanced tool materials. Today these bald facts are given impressive acronyms (HPC for high-performance cutting and MQL for minimal-quantity lubrication) and at IMTS their growing significance and considerable advantages were highlighted by Guhring.
Interestingly, powder metallurgists who machine presintered parts are particularly well acquainted with dry machining, since any cutting lubricant would quickly be absorbed by sponge-like work material.
Trent showed by clever photomicrography that, in high-speed machining of steel, the chip's boundary layer flows in “a state of seizure” around the cutting edge, which was therefore never quite reached by coolant. With reamers, however, Guhring claims that its “MQL system ultimately enables the optimal delivery of the coolant to the cutting edge”.
Guhring's innovative tools for HPC and MQL include HR500D and HR500S high-performance reamers, for through and blind holes respectively. The solid carbide reamers ream holes at cutting rates previously reserved for cermet tools but are considerably more versatile. Standard diameters are from 4 to 20mm, with H7 tolerance.
The specially developed straight flute geometry of the HR500D, unique with reamers for through holes, permits extremely high cutting rates. Straight-flute geometry and exceptional coolant delivery support problem-free chip evacuation ahead of the cutting edge. Because no chips return within the flutes, the reamed surface is optimally preserved. Coolant supply is through longitudinal flutes ground externally on the reinforced hardmetal shank, aligned to each reamer flute. Advantages over internal cooling via radial coolant ducts include improved rigidity, no flow restrictions through eroded or sintered cooling ducts, and no blockage by lodged chips of the coolant-duct exit holes. Optimal coolant delivery is maintained even with re-ground tools and clamping is unaffected in hydraulic or shrink-fit chucks.
Excellent results were achieved in reaming a 65mm deep through hole with 4.485mm diameter —reaming depth over 14×D - in steel valve blocks. Machining time was reduced by 31 seconds to just 1.1 seconds per hole. Cutting speed increased from 18 to 120 m/min, feed rate from 0.12 to 0.4 mm/rev and tool life from 15 to 60m. Concentricity was below 4μm.
The solid carbide HR500S reamer for blind holes differs in having internal cooling via a central coolant duct. Its especially large cross-section ensures optimal delivery of the coolant to the cutting edge. Straight-fluted tool geometry and efficient coolant supply ensure safe chip evacuation. Cooled with soluble oil at a pressure of 40 bar, typical cutting speed and feed rate were 250 m/min and 1.0mm/rev, compared with the previous best, 25 m/min and 0.2mm/rev.
Kennametal
Kennametal and its subsidiaries seldom disappoint in the innovation stakes. Of interest to Metal Powder Report readers are new tool materials, improved coatings and developments in tool and insert design.
‘Beyond' description
Though officially released since the Chicago show, we can hardly omit Kennametal's new Beyond range of more than 2000 high-performance inserts and other turning products. Thanks to higher metal-removal rates and extended tool life, these products are claimed to push productivity 30% or more higher for a broad spectrum of metalworking users. The product line includes 11 new grades (Table 1), applicable to steel, stainless steel, and cast-iron turning applications, their designations being based on and selected from the listings in ISO standard 513. The range is apparently to be further extended to milling and hole-making tools.
Unfortunately, not too many hard facts and figures have been released. Those gleaned indicate that a post-coating surface treatment improves edge toughness, reliability and depth-of-cut notch resistance. It also micro-polishes the surface to reduce friction and workpiece sticking. A low-stress, fine-grained alumina topcoat allows increases in cutting speed, improving productivity and reliability at high cutting temperatures. All Beyond inserts are top- and bottom-ground after coating to improve surface seating in the toolholder.
Kennametal claims to have carried out many successful tests around the world, in a variety of industries, during this development, but regrettably little solid or detailed information had been made available as this feature went to press.
Ceramics with whiskers
Equally interesting are Kennametal's non-hardmetal new releases. First of these is the KY4300 ceramic, an updated version of an old technology, SiC whisker-reinforced alumina. Some manufacturers long ago abandoned this composition because of worries about the possible cancer-inducing propensities of the silicon carbide fibres, similar in size to those of asbestos. There's no problem, of course, for users of finished inserts. Machining applications include superalloys, chilled rolls with especially abrasive surfaces and grey cast irons for brake drums and the like.
Superhards
Kennametal introduced two new solid PCD (polycrystalline diamond) grades KD1400 and KD1425, complementing the existing KD1405, with CVD diamond coating on hardmetal, and replacing the older KD100 and KD108.
KD1400 is claimed to be much finer than competitive “fine-grained” PCD, typically 1μm average grain size compared with 2μm for the competition. KD1425 is quite different, a so-called ‘multi-modal' grade. What does this mean? In normal hardmetals, liquid-phase sintering entails preferential solubility of the finest carbide grains as the temperature goes up, then preferential deposition on the coarsest grains as the compact cools from sintering temperature. With diamond, there is little or no solubility and it makes more sense to encourage densification by an alternative method. In this instance, a mixture of grains of different sizes enables the gaps between larger particles to be filled by smaller particles, and the gaps between those to be occupied by microfines. Apparently the theory works.
Kennametal has also revised and rationalised its complete range of PCBN cutting inserts. Interestingly, although the hardness of cubic boron nitride is second only to that of diamond, commercial PCBN compositions almost always contain a second softer phase as binder, either metal or ceramic. Thus the cutting performance of an insert may benefit from an applied continuous CVD or PVD coating.
Each grade designation begins with the letters KB, followed by a four-digit code. The first of these indicates the surface — 1 for uncoated, 5 for PVD-coated, 9 for CVD — and the last three the CBN content — 610 for low, 625 for medium, 630 for high. Thus a medium content grade with PVD coating would be designated 5625. Uncoated inserts give the best surface finish, PVD reduces chipping and crater wear, whilst CVD also improves thermal stability and is preferred at higher cutting speeds. The low-content grades appear not to be available as-coated.
As an additional variable, inserts can be solid PCBN, hardmetal with a single PCBN cutting corner, with multiple cutting corners (two, three or four) or a complete face of PCBN with hardmetal backing.
Sandvik Coromant
Like Kennametal, Sandvik Coromant is a world power in cutting tools and a technological leader in sintered cutting-tool materials. Here are a few recent examples, as shown and demonstrated at IMTS in Chicago. Even Sandvik would admit, however, as grudgingly would all its competitors, that on this occasion its biggest success was a bright yellow giveaway canvas satchel for catalogues and other documents, not to mention pens and mobile phones. Many thousands were eagerly snatched up by exhibition visitors.
Milling hardened steels
Sandvik Coromant's new GC1010 insert grade was designed to provide a productive cutting solution when milling hardened steel. With capabilities ranging from roughing to finishing, GC1010 was developed in response to growing demand from the die and mould industry. To provide the toughness and wear resistance necessary to maximise performance in hardened steel, GC1010 features a thin PVD coating combined with a fine-grained hard substrate. This increases metal removal rates, boosts tool life and provides sustained surface finish and tight tolerances during long cutting cycles.
Wiper inserts boost productivity and quality
Sandvik Coromant's innovative WMX wiper inserts offer increased productivity and quality across a broad range of applications. The WMX wiper insert combines a main radius with multiple complementary radii and integrates new chip-breaker geometry. This design widens feed-rate and chip-breaking ranges, allowing machining times to be cut by approximately 30%. Productivity is increased in medium- to rough-machining and much higher quality surface finishes can be achieved in finishing operations.
Face-milling flexibility
Available in early 2009, the CoroMill 345 is a flexible tool providing high-performance face cutting with small depths of cut in steel and stainless steel. It offers high performance across a spectrum of applications ranging from small-batch, mixed machining to high-volume dedicated production lines. As part of a new generation of 45-degree face mills, the double-sided inserts provide four edges on each side. The complex insert design provides more positive axial inclination at small depths of cut, resulting in soft cutting action with low axial pressure on the workpiece. As depth of cut becomes larger, a more upright part of the cutting edge is engaged. The tool will be released in early 2009 in diameters from 40 to 250mm.
Cast iron milling
The CoroMill 365 is a close-pitch face-milling cutter for roughing to semi-finishing of cast iron components. The tool is best utilised in large series production or in applications requiring rapid removal of high metal volumes, offering up to 6mm depth of burr-free cut. It provides high accuracy through a strong and stable cutter body and precision ground inserts with eight true cutting edges. The mill is available in diameters ranging from 50 to 160mm.
Vibration-free machining
Sandvik's solution to vibration problems when machining with long slender tools is an integrated vibration-dampening module in the CoroMill 390 milling cutter, to improve performance in deep cavities and pockets. This stabilises the machine and improves utilisation for face and shoulder milling, especially in long overhangs. Reducing vibration in often tricky operations creates the confidence needed to increase cutting parameters without compromising workpiece quality. Attributes of the CoroMill 390 include improved component surface finish and longer tool life. It's noteworthy that Sandvik has enough confidence in these tools to engrave the word “silent” on their bodies. Stocked diameters are 20, 25, 32 nd 40 mm.
Seco Tools
Seco extended its Duratomic range with the new MP1500 grade, enhancing steel-milling performance by achieving more parts machined in less time. Field tests comparing the MP1500 to its replaced grade showed 135-200% increase in output and 150% increase in tool life.
The so-called Duratomic process for hardmetal cutting inserts produces an alumina coating with “unique” (though unspecified) atomic structure and an advanced combination of toughness and wear resistance. MP1500 is a relatively low cobalt, hard and wear-resistant grade for machining harder steels, including tool steels or even difficult types of cast iron. Apparently Duratomic coating technology reduces the heat transferred during the cutting process, enabling higher cutting performance to be attained. MP1500 is offered in a wide range of insert geometries to cover face, square shoulder, disc, high-feed and copy-milling applications.
Seco's family of milling cutters has been extended by the Double Octomill R220.48 with double negative indexable inserts. Each has 16 cutting edges, making the tool extremely economical. Low costs per edge and high feeds increase productivity as a roughing tool, or with adjustable wiper insert as a roughing/finishing tool for cast iron and steel. In the same series, the R220.44 model is characterised by higher chip removal rates, slim cutter body, super-narrow pitch and simple handling, whilst the R220.88 with 88° rake angle enables machining to be carried out close to thin walls at high chip-removal rates.
Solid carbide milling cutter
An extended range of Seco Mini milling cutters, for both ball nose and shank style cutters, with and without corner radii, starts from a diameter of 0.2mm and is available in different L/D ratios, corner radii and shank diameters. The Mini range allows optimum selection of the correct cutting tool for micro-machining of steel, stainless steel, hardened steel, aluminium, titanium, graphite and copper.
Valenite
High performance microstructure
Termed “revolutionary” — perhaps because its submicron microstructure appears somewhat better than that usually resulting from attriting — Valenite (Valenite Safety in Europe, since the merger announced at EMO 2007) VP2003 is said to be “a special carbide grade technology of powder preparation and sintering.” Allied to a heat-resistant AITiN-based coating, VP2003 has improved thermal resistance that provides exceptional stability against thermal cracks and plastic deformation. VP2003 offers versatility on difficult-to-machine workpiece materials including steels, stainless steels, heat-resistant superalloys, as well as aluminium and non-ferrous materials. This general-purpose milling grade also works exceptionally well in die and mould applications.
VP8515 and VP8525 insert grades were designed specifically for high-speed, high-productivity turning operations for finishing and semi-finishing stainless steels and other heat-resistant alloys.
The V420 ball-nose endmill with SideLok, a three-insert, indexable, profiling milling cutter, reduces machining time by up to 33%. The V420 utilises the SideLok direct insert clamping design to securely mount inserts into this three-effective, ball-nose cutter for increased feed and metal removal rates in both finishing and semi-finishing operations.
Expanding Valenite's general purpose Penta family of five-sided, face-milling cutters is the V560 heavy-duty roughing facemill. The 10mm depth-of-cut capability lets customers machine under the tough outer layer of forged or cast workpieces, reducing insert wear. Thus the V560 offers higher material removal rates while using less horsepower.
VForce with SideLok high-performance milling cutter has a clamping design with high insert density that increases metal removal rates, providing quicker indexing and reducing spare parts inventory. Versatile with diameters from 80mm to 250mm, feed and material removal rates are up to three times faster than tools with traditional insert-clamping systems.
The VFlash high-velocity milling cutter for high-speed machining of aluminium and non-ferrous alloys was developed for quick and accurate indexing, as well as achieving operating speeds up to 6000 surface m/min — rates for optimal utilisation of tipped polycrystalline diamond (PCD) inserts. Cubic boron nitride (PCBN) inserts are also available for finishing cast iron and hardened steel.
Walter
Tiger teeth turn cast iron
Technological improvements in the manufacture of carbide substrates and coatings have further improved the wear resistance of the WAK10 grade for cast iron turning. Walter recommends this cutting material for achieving maximum cutting output under good machining conditions. An improved heat-resistant substrate and 100% thicker aluminium oxide coating permit higher cutting speeds and extend tool life. The enhanced properties of WAK10NEW are due not only to an improved substrate but also and primarily to a patented intermediate layer in the coating structure. Productivity gains have been as much as 75%.
Octagon cutter in Walter's Xtra.tec
With the new F4080 Walter AG has added an octagon cutter with eight cutting edges per insert and 43°approach angle, with wide and medium tooth pitches. One insert size covers all cutter diameters from 40 to 160mm. WSP45 and WSM35 grades are suitable for high-alloyed steel, stainless steels and difficult-to-cut materials and inserts in five geometries from “strong” (unfavourable cutting condition) to “sharp” ( aluminium materials) are available for precise adjustment.
