Hard Metal Alloys Research Articles

Advanced Machining of Joint Implant UHMWPE Inserts

The modern orthopaedic implants for applications in hips, knees, shoulders, and spines are composed of hard metal alloys or ceramics and a tribological sub-component that is made of soft materials, with good frictional properties—e.g., UHMWPE (Ultra High Molecule Weight Polyethylene). The UHMWPE implants need to be machined into their final shape after the polymerization and consolidation into a blank profile or near net shaped implant. Thus, machining is a crucial technology that can generate an accurate and precise shape of the implant that should comply with the joints’ function. However, the machining technology can affect the topography and integrity of the surface, transmitted stresses, and resistance to wear. Technology, cutting tools, and cutting conditions can have an impact on the physical and mechanical properties of the entire implant and its longevity. This paper shows an effective and competitive technology for acquiring high-quality insert shape, dimensions, and surface, needed especially for customized implants.

Effects of swift heavy ions at different fluencies on WC-6Co hard metal alloy

Tungsten carbide hard metal alloy with 6% by weight cobalt was studied before and after irradiation at different fluencies with 167 MeV132Xe ions. Raman spectroscopy, X-ray diffraction, neutron diffraction and positron lifetime spectroscopy were employed in order to assess the microstructural evolution in the material upon irradiation fluence increase. Analysis of the Raman spectrum for the pristine, non-irradiated material unveils that the surface is composed of a graphite-like phase and highly oxidized tungsten atoms spread in the carbon matrix. All characteristic peaks of tungsten carbide (WC) and possible cobalt phases are either missing or strongly overlapped in all Raman spectra. Bonding between tungsten and oxygen atoms broke upon irradiation and total deoxidation of the surface is detected for the two highest fluencies investigated at 5 × 1013 ions/cm2 and 3,83 × 1014 ions/cm2. Increasing the irradiation dose causes amorphization of the carbon phase on the surface accompanied by “up and down” trend of change in carbon cluster size. The Raman spectra analysis also unveils, that molecular nitrogen (N2) from the atmosphere penetrates the carbon matrix upon irradiation. The results from the X-ray and neutron diffraction reveal that the main phase in the material is δ-WC and also give information about changes of the lattice parameters with increasing fluence. Reorganization of the induced point defects to dislocation defects as a function of the irradiation dose is discussed, but no phase transition of the main δ-WC phase is detected. Steady increase of compressive internal stress with increasing irradiation dose is noted by XRD. The tendency is not monotonic and the stress leans towards saturation at the highest fluence, with the highest value of −5.26 GPa. The Positron lifetime spectroscopy measurements show the presence of short lifetime component ranging from 170 ps to 190 ps, interpreted as small vacancy clusters. The intensities of the different positron lifetime components vary with the irradiation dose non-monotonically.

Exceptionally durable and hard metal alloys discovered with combination technique

By exploiting the synergy between machine learning and high throughput experimentation, scientists discovered exceptional metallic glass alloys.

On the Machining of Joint Implant UHMWPE Inserts

The modern orthopaedic implants for applications in hips, knees, shoulders, and spines are composed of hard metal alloys or ceramics. The tribo-logical sub-component is composed of soft materials with good tribological properties – e.g. UHMWPE (Ultra High Molecule Weight Polyethylene). The UHMWPE implants need to be machined into their final shape after the polymerization and consolidation into a blank profile or near-net shaped implant. So machining is a crucial technology that can generate an accurate and precise shape of the implant that should comply with the joints’ function. However, the machining technology can affect the topography and integrity of the surface, and its resistance to wear. The technology, cutting tools, and cutting conditions can impact the physical and mechanical properties of the entire implant, limiting its life span and creating a need to be replaced. The basic machining technologies are turning and milling (each can be used as roughing or finishing). There are many ways to machine these surfaces. Many problems such as low rigidity of the product, poor thermal properties of the material, high melt viscosities, and sticking of the material to the cutting edge (production of built-up edges) have been solved. UHMWPE can be damaged by excessive heat, feed rate, cutting force, and tool micro-geometry. The shapes and dimensions for the customized implants vary broadly for the humans this complicates the machining technology. No standard programs can be used repeatedly so each joint must be designed and produced individually. However, it results in the longer implant life and a better comfort of patients.

Investigation of characteristics and properties of spark plasma sintered ultrafine WC-6.4Fe3.6Ni alloy as potential alternative WC-Co hard metals

The present study proposed the fabrication of a WC-6.4Fe-3.6Ni hard metal alloy using spark plasma sintering (SPS) as a potential alternative to the WC-Co hard metal. Fe-36%Ni powder (mean particle size 26.9 μm) was produced from Fe and Ni commercial powders via high energy milling and the effect was analyzed. WC-6.4Fe-3.6Ni (alternative grade) and WC-Co (reference grade) were obtained from ultrafine WC powder (particle size 0.45) with 10%wt binder. SPS sintering of WC-6.4Fe3.6Ni was performed at 1100, 1200 and 1300 °C with a holding time of 5 min achieving 99.8% higher densification at 1300 °C and WC-Co was sintered at 1200 °C. The results show that increasing the sintering temperature enhanced the microstructure and hardness with a decrease in fracture toughness. The wettability of milled Fe-Ni binder during heating in the SPS process contributes to enhance densification and properties. The decrease in fracture toughness is attributed to a decrease in the binder mean free path. The XRD analysis showed that η phase was not detected for either composite grades. Studies of sintering kinetics were applied to determine the sintering mechanisms involved in the final stage of sintering, which can be elucidated by calculating the slope exponent (n) from the relationship between the shrinkage rate and sintering time. Slope exponent consistent with WC diffusion in the liquid phase was found for WC-6.4Fe-3.6Ni sintered at 1300 °C. Good properties was found for WC-6.4Fe-3.6Ni sintered at 1300 °C, showing higher hardness ~1633 HV30 and fracture toughness ~11 MPa m0.5. WC-6.4Fe-3.6Ni sintered at 1200 °C has superior hardness (1786 HV30) than WC-Co (1689 HV30). A comparison of these properties with results from similar grades in the literature shows that the WC-6.4Fe-3.6Ni alternative grade has optimal properties and can be adopted as an alternative to WC-Co grades.

Experimental Study on the Diagnostics of Internal Compressible Flows using Outer Surface Nozzle Temperature

Cold spray (CS) is one of the thermal spraying methods which make coatings by spraying melted minute particles on substrate surfaces. Solid particles are sprayed onto a substrate at high speed to form a coating accelerated by a supersonic gas flow using a convergent-divergent nozzle. Therefore, it is important to understand the gas flow condition inside the nozzle that accelerated the gas flow. However, diagnosing internal gas flow is almost impossible for commercial CS nozzles because the nozzle is fabricated with hard metal alloy to prevent abrasions of the nozzle. Therefore, it is impractical to drill pressure taps to the CS nozzle to diagnose the gas flow. To solve this problem, authors propose non-intrusive flow-diagnostic methods which uses outer surface temperature of the CS nozzle and temperature recovery factor of the working gas. This research shows that the accuracy of this method is improved by measuring the outer surface temperature of the entire axial direction of the nozzle, and that the temperature recovery factor of the internal flow depends on the stagnation pressure. Therefore, the temperature recovery factor of the internal flow should be treated as a function of stagnation pressure.

Technical feasibility of hard coating by flux-cored arc welding on a sugarcane cutting knife

The sugarcane agroindustry covers 10,184,340 ha of arable land in Brazil. Harvesting this crop requires increasingly sophisticated equipment and sugarcane uses a basal cutting system with knives. These knives deteriorate rapidly due to abrasion with silica in the soil, which makes hard coating feasible for these components. Hard coatings generally involve the addition of chromium to increase the service life of agricultural machinery parts. The need to reduce the levels of chemical elements harmful to humans and animals in agricultural soils requires a study of alternatives to substitute chromium in hard metal alloys. Based on that, this work is aimed to investigate an alternative this respect; the present study proposes a change in coating from tungsten carbide paste (WC), which contains chromium, to a titanium carbide–based coating without chromium. To this end, FCAW (flux-cored arc welding) welding process was used, with self-shielding flux-cored wire containing alloy elements that increase resistance to abrasion, thereby extending the service life of the component. Simultaneous optimization of multiple responses was used to determine proposed welding parameters. For validation purposes, abrasion wear tests with a rubber wheel and dry sand were conducted to compare resistance to abrasion between the proposed material and that used in commercial knives. Results from accelerated wear tests showed FCAW higher performance (around 48%) compared to the WC coating. This demonstrates technical feasibility of the proposed hard metal deposition process using FCAW welding aimed to increase the service life of basal cutting knives without chromium.

Band Wear and Effects on Recovery and Survival Estimates of Diving Ducks

ABSTRACTWildlife biologists commonly use marked individuals to estimate population size and vital rates. If markers are lost or become too illegible to be reported (which we define as functional loss), population size and vital rates derived from marked individuals could be biased. We double‐banded 4,990 lesser scaup (Aythya affinis) and 1,429 redheads (A. americana) with a traditionally used band made of aluminum, plus another band made of incoloy designed to be more resistant to wear. Banding took place at 10 late‐summer banding stations in the northcentral United States and Canada during 2009 and 2010 and during spring at Pool 19 on the Mississippi River, Iowa, USA, during 2009–2011. We then examined bands recovered from hunter‐shot birds to assess wear of paired bands. We also conducted band‐recovery analyses to test for differences in band retention and reporting rates between birds banded with aluminum versus hard metal bands. Band wear assessments indicated that incoloy bands lost zero mass over time and showed no effects of wear. Although no bands were lost, aluminum bands showed significant mass loss and wear over time. For double‐banded lesser scaup recovered in their fourth year after banding, 71.9% of aluminum bands had contact information that was completely unreadable, compared with only 12.5% for those worn by redheads. Based on our recent double‐band recovery data, up to 34% of lesser scaup bands would be recovered during the fifth through eighth hunting seasons of band wear. Band wear affected estimated recovery rates of both species, with stronger effects in lesser scaup. Our results indicate that use of aluminum bands resulted in a substantial loss of information; thus, banders should only use bands made of hard metal alloys (e.g., incoloy or stainless steel), and discontinue all use of aluminum bands for these species and other diving ducks with sparse recovery data. Future demographic analyses using banding data for species with excessive band wear and low numbers of band‐recoveries should account for band type and functional band loss. © 2020 The Wildlife Society.

New bio-based nanolubricants for turning of Inconel 718 towards improvement of tool wear resistance and specific cutting energy

Substitution of traditional metal cutting fluid with newly formulated bio-based nanolubricants for machining hard-to-cut material such as Inconel 718 can be advantageous in reducing the impact on environmental as well as on the overall operating or machining expenditure. Added to that, combination of nano-lubricants with Minimum Quantity Lubricant (MQL) system provides benefit towards controlling fluid consumption along with the aim of cooling and lubricating effectively at the cutting zone. Until now, research studies on the ability of bio-based nano-lubrications for cutting fluids application on hard metal alloys are still at infancy. Hence, in this work, newly formulated bio-based nano-lubrications were tested while machining Inconel 718 with uncoated carbide tool. Performances of different cutting fluids namely; Solcut oil, coconut oil, pure bio-based oil, bio-based oil + 0.2% Al2O3, bio-based oil + 0.5% Al2O3 and bio-based oil + 0.8% Al2O3 were evaluated with respect to tool wear and specific cutting energy. Overall, bio-based oil + 0.8% Al2O3 exhibited excellent wear resistant which prolong the cutting time or the tool life expectancy. Meanwhile, bio-based oil + 0.5% Al2O3 was superior in lowering the specific cutting energy for machining Inconel 718 as compared to other five types of cutting fluids.

SPS hard metal alloy WC-8Ni-8Fe fabrication based on mechanochemical synthetic tungsten carbide powder

The paper presents fabrication of WC-Ni-Fe hard metal alloy with the density up to 99.9% from theoretical, hardness ∼1303 HV, fracture toughness ∼12.4 MPa m0.5, compressive strength ∼1365 MPa and without open porosity. High quality of the materials is provided by the original synthesis route based on powder preparation and sintering. WC powder (particle size 0.1–14 μm) was obtained via mechanochemical synthesis using available precursors and polymethyl methacrylate to enhance the grinding. Rapid SPS consolidation was performed at 1200 °C and below achieving high density with the holding time being less than 18 min. Increased amount of Ni–Fe (8 wt% of each component) was used to enhance SPS heating due to deep wetting of the particles and, therefore, improved conductivity of the whole system. Earlier unknown data on densification dynamics and phase composition are presented for WC-8Ni-8Fe alloy under SPS sintering in the temperature range 1100–1200 °C. The results are proved by the means of XRD, SEM and EDX.

Investigation of contact dermatitis caused by hard metal dust

Objective: To investigate the incidence of contact dermatitis among workers in cemented carbide production enterprises. Methods: From October 1997 to October 2017, an occupational epidemiological survey was conducted on a large-scale cemented carbide production enterprise, and occupational health examinations were conducted for employees. 152 people were exposed to hard metal dust (hard metal raw material dust and alloy dust) . The employees in the work group were contact groups, and 142 employees in the non-dusting operation of the company were in the control group. A detailed retrospective survey of hard metal production workers with contact dermatitis history in the two groups was conducted to analyze the risk factors of contact dermatitis exposure to hard metal dust. Results: The incidence of allergic diseases in the exposed group was significantly higher than that in the control group. The difference was statistically significant (χ(2)=23.793, P<0.05) . The incidence of contact dermatitis in the exposed group was significantly higher than that in the control group. The difference was statistically significant (χ(2)=24.659, P<0.05) ; the changes of contact dermatitis in the contact group were mainly allergic contact dermatitis, and some showed irritative contact dermatitis; the operator had respiratory symptoms (including work-related nasal congestion, cough, wheezing) , difficulty breathing may be the influencing factors of contact dermatitis (RR=2.60, 95%CI: 1.10-6.20, P<0.05) . Conclusion: Hard metal alloy enterprises are exposed to hard metal dust. The incidence of contact dermatitis is high in workers, and the occurrence of contact dermatitis may be associated with those with respiratory symptoms.

On the Critical Assessment into Damage Behavior of a WC–Co Hard Metal Alloy Used in the Form of Rock Drill Bits

Cemented carbide possesses a good combination of wear resistance, strength and toughness. Therefore, it is mainly used as a tool material. During rock drilling and coal cutting operations, the cemented carbide undergoes a complex condition which limits the service life. It has been an interesting area of research to characterize different wear mechanisms in various working environments. The durability of the cemented carbide has been tested after using it for rock drilling, coal cutting and laboratory wear testing. The present work deals with rock drilling experiments. Granite samples were drilled by using three different grades of cemented carbides (possessing 5, 10 and 15% cobalt) based twist drill bits. All the experimental parameters were kept the same for each sample. After drilling, suitable samples of worn-out cemented carbides were prepared for examining under field emission scanning electron microscope and energy-dispersive spectroscopy. A critical characterization of wear mechanisms was performed. An attempt was made to identify wear behavior among the three grades of cemented carbide.

Retention of old technologies following the end of the Neolithic: microscopic analysis of the butchering marks on animal bones from Çatalhöyük East

ABSTRACTMicroscopic analysis of butchering marks on bones from Neolithic to Hellenistic deposits at Çatalhöyük, Turkey, are employed as a proxy measure for identifying the rate and nature of adoption of metallurgy for quotidian activities. During the Neolithic and Chalcolithic periods, only stone tools were being used for butchering. In the post-Neolithic strata, however, chipped stone tools continue to dominate the assemblage. This stands in contrast to the larger regional pattern where metal butchering marks dominate after the end of the Early Bronze Age. The authors propose that the continued use of stone tools for processing animal carcasses long after the advent of hard metal alloys is because of the nearby and abundant source of obsidian. Obsidian flake and blade tools remain the raw material of choice for animal-carcass processing over time. The analysis demonstrates that the replacement of stone and adoption of metal butchering tools was not a straightforward affair.

Novel High-Performance CVD Coatings for Machining Applications

Abstract Investigations of hard and wear resistant materials have a long tradition to increase the performance and profitability of machining applications. The evolution started with WC-Co hardmetal alloys, which were produced by PM technology, followed by CVD coatings on hardmetal tools. The first CVD coatings applied were TiC, TiN and Al2O3. The properties of these coatings could be optimized by varying the crystal size, crystal orientation but also combination of the materials in multilayer systems. Nowadays, about 85% of all hardmetal tools are coated.During the last years, driven by PVD coatings showing good performance (e.g. TiAlN), the search for new CVD coatings was intensified. Medium temperature (MT) CVD processes for TiCN allowed the deposition of TiCN crystals with different composition side by side. Due to this microstructure the adhesion between single layers in new multilayer coatings like TiN/MT-TiCN/Al2O3/TiN could be increased. Novel (Ti,Al)N coatings were developed, showing a nanolamellae microstructure consisting of self-assembled (Ti,Al)N with different composition. For the future there is still plenty to investigate. The already existing coatings and coating systems have to be optimized for the various machining applications. To find new types of CVD coatings, we look for chemical reactions practicable for its use in CVD equipment.

Visualisation and measurement of hardmetal microstructures in 3D

2D and 3D measurements of two WC-Co hardmetal alloys have been made using electron backscatter diffraction and focused ion beam microscopy. The 3D network of the Cobalt binder phase has been shown to be comprised of both small isolated Co grains as well as the large interpenetrating grains previously surmised to exist from 2D mapping; grain boundaries between the large Co grains have also been observed for the first time in 3D. 2D and 3D WC grain size distributions are shown to correspond closely, but only if the measurements of small grains are discounted as few grains below about 40% of the mean size are seen in 3D, even though much smaller sections are seen in 2D views. Analysis of grain shape has found the presence of truncated trigonal prisms with faces having the expected basal and prism plane orientations, but it also reveals complex shapes produced by multiple adjacent grains of almost identical orientation.

Study on the sintered characteristics and properties of nanostructured WC–15 wt% (Fe–Ni–Co) and WC–15 wt% Co hard metal alloys

In this work, four different vacuum sintering temperatures (1250 °C, 1300 °C, 1350 °C and 1400 °C) were studied to determine the optimal process parameters of nano WC–15 wt% (Fe–Ni–Co) and WC–15 wt% Co sintered hard metal alloys. Experimental results showed that the optimal sintering temperatures for nano WC–(Fe–Ni–Co) and WC–Co alloys were 1300 °C and 1350 °C for 1 h, respectively. The sintered nano WC–(Fe–Ni–Co) and WC–Co hard metal alloys showed a good contiguity of 0.44 and 0.42; hardness was enhanced to HRA 90.83 and 90.92; the transverse rupture strength (TRS) increased to 2567.97 and 2860.08 MPa; and KIC was 16.23 and 12.33 MPa√m, respectively. Although the nano WC–(Fe–Ni–Co) alloys possessed a slightly lower TRS value, they exhibited superior fracture toughness (KIC) and hardness similar to that of the nano WC–Co material. Significantly, nano WC–(Fe–Ni–Co) alloys could be sintered at a lower temperature and still retained their excellent mechanical properties.

Electrochemical Leaching of Tungsten from Hard Metal Alloy Using Molten Sodium Hydroxide

Hard metal alloy, which is used as material for cutting tools, comprises tungsten carbide, cobalt, and other elements and possesses excellent hardness and heat resistance. Hard metal alloy is difficult to recycle, and its rate of recycling in Japan is low. In this study, components of hard metal alloy were leached by electrolysis in molten sodium hydroxide. The optimum experimental condition was potentiostatic electrolysis at an oxidation potential of ¹0.7V. Tungsten constituted 99.7mass% of the leached component in the molten salt, and other metals oxidized to passive materials. Tantalum was dissolved in the molten salt without electrolysis. Chromium was oxidized from its metal state to its trivalent oxide, which was converted to the hexavalent oxide by trace oxygen in the atmosphere of the reactor. [doi:10.2320/matertrans.M2014316]

Investigation into the sintered behavior and properties of nanostructured WC–Co–Ni–Fe hard metal alloys

Nanomaterials normally possess high strength, high hardness and excellent ductility and toughness. In the research, various vacuum sintering temperatures (1250°C, 1300°C, 1350°C and 1400°C) were explored in order to investigate the optimal parameters of micro- and nano-WC sintered composites; and further to compare the sintered behavior and properties of two different sizes of WC materials. All specimens were fabricated by using vacuum sintering of the powder metallurgy technique. The experimental results show that micro- and nano-WC specimens generated a good liquid-phase sintering at 1350°C sintered for 1h, and thus, exhibited excellent mechanical properties. The porosities were decreased to 0.36% and 0.8%, the hardness was enhanced to 90.1 and 91.4HRA and the TRS was increased to 1441.62 and 1540.56MPa, respectively. Since there is an effect upon the grain refinement, nano-WC obviously possesses better performance than the micro-WC hard metal alloys. Meanwhile, the KIC value for sintered nano-WC dramatically increased to 12.71MPam1/2.

Rough turning Inconel 750 with supercritical CO2-based minimum quantity lubrication

This paper describes preliminary results of replacing water-based (aqueous) flood coolant with supercritical CO2-based minimum quantity lubrication (scCO2 MQL) in an external turning operation on an Inconel 750 combustor housing. Two series of tests were performed: the first series to compare tool wear performance observed with aqueous flood coolant and scCO2 MQL under identical machining conditions, and the second series to investigate tool wear performance with scCO2 MQL at higher metal removal rates (MRR) than the MRR used in production practice with aqueous flood coolant. All tests were performed using roughing cuts on unaged Inconel with coated carbide tooling, and vegetable oil lubricant. As a key enabler, special flank jet tool holders were used to eliminate chip blockage of the lubricant stream.In the first series of tests, tool wear was observed to be consistently lower with scCO2 MQL than with the aqueous flood coolant. In the second series of tests, two process conditions were demonstrated for which MRR increased by 25% and 40%, respectively, with scCO2 MQL compared to aqueous flood coolant at equivalent tool life. Notch wear, the limiting factor for tool life under baseline conditions, was reduced for scCO2 MQL, but crater wear and chip hammering were more pronounced. Overall the results indicate that scCO2 MQL can provide increased tool life or material removal rate compared to aqueous flood coolants when machining Inconel 750 and similar nickel alloys by improving lubricity and changing the dominant wear mechanism from rapid notch wear to gradual crater wear and chip hammering. These tests, which involved extended cuts of over 10min under production conditions, represent an important extension of MQL machining to a hard metal alloy that cannot be machined by conventional MQL methods.

Characterization and properties of sintered WC–Co and WC–Ni–Fe hard metal alloys

• WC–Ni–Fe alloy sintered at 1400 °C had the highest hardness (HRA 85.3 ± 0.5). • The optimal WC–Ni–Fe sintered alloy possessed the highest TRS value (2524.5 ± 1.0 MPa). • The fracture toughness of the sintered WC–Ni–Fe alloys is mainly provided by the Ni–Fe binders. • WC–Ni–Fe sintered alloy possessed the highest fracture toughness of K IC (15.1 MPa m 1/2 ). • The WC–Ni–Fe sintered alloy had the much better corrosion resistance in 0.15 M HCl solution. The aim of this study is to explore two different tungsten carbide binders (Co and Ni–Fe) and then impose various sintering temperature treatments. Experimental results show that the optimal sintering temperatures for WC–Co and WC–Ni–Fe hard metal alloys are 1350 °C and 1400 °C for 1 h, respectively. Meanwhile, the WC–Co and WC–Ni–Fe alloys undergo a well liquid-phase sintering and, thus, exhibit excellent mechanical properties. In addition, the sintered WC–Co and WC–Ni–Fe alloys show that when the relative density reached 99.76% and 99.68%, the hardness was enhanced to HRA 84.4 ± 0.5 and 85.3 ± 0.5, and the TRS increased to 2471.2 ± 1.0 and 2524.5 ± 1.0 MPa, respectively. Moreover, the corrosion test results show that the WC–Ni–Fe alloy sintered at 1400 °C had the lowest corrosion current ( I corr ) of 1.11 × 10 −5 A cm −2 and the highest polarization resistance ( R p ) of 2464.61 Ω cm 2 in 0.15 M HCl solution. Simultaneously, the fracture toughness of K IC increased to 15.1 MPa m 1/2 . Compared with sintered WC–Co alloys, the sintered WC–Ni–Fe hard metal alloys possessed much better corrosion resistance and mechanical properties.