Applications of WC-based composites rapid synthesized by consumable electrode in-situ metallurgy to cutting pick

doi:10.1016/j.ijrmhm.2012.05.005

International Journal of Refractory Metals and Hard Materials

Volume 35, November 2012, Pages 132-137

$International Journal of Refractory Metals and Hard Materials$

https://doi.org/10.1016/j.ijrmhm.2012.05.005 Get rights and content

Abstract

The composite W_pC (WC + W₂C) material was prepared by the rapid route of consumable electrode D.C. arc in-situ metallurgy in the blind hole of the cutting pick, which has excellent metallurgical bonding with the substrate. The microstructure and microhardness of W_pC were investigated by XRD, EDS, TEM and microhardness tester. The crystallization mechanism was analyzed. The results show that the microstructure of the sample is uniform, and the hard phases are WC, W₂C, Fe₃W₃C. The average hardness of the alloy is 1290 HV_0.2 and the average microhardness of W_pC is 2253HV_0.2. The two-dimensional microstructure morphology of W_pC is triangluar and rectangular. The largest W_pC grains can grow to 70 μm in the molten pool.

Highlights

► W_pC composite is prepared by the consumable electrode D.C. arc in-situ metallurgy. ► The CDISM is a low cost and high efficiency rapid route. ► The average microhardness of the W_pC phase is 2253 HV_0.2. ► The composite has excellent metallurgical bonding with the substrate.

Introduction

Due to the excellent properties of high hardness, low coefficient of thermal expansion, high wear resistance and corrosion resistance, WC-based hardmetals are widely used in various engineering applications, such as cutting tools, mining tools, rock drill tips, moulds and as well as general wear parts [1], particularly for coarse-grained grades usually used in mining tools for its standout abrasion resistance, red hardness and good toughness [2], [3], [4]. Cutting picks usually work under extremely harsh operating conditions including high temperature, high impact loads, intense abrasive wear and severe fatigue. The wear and failures of hardmetal inserts in cutting picks are the major factors determining the effectiveness of mining tools [4].

WC-based hardmetals are usually fabricated by the powder metallurgy (PM) technique, which involves mixing of elemental powder, pressing, and sintering [5], [6]. To obtain high densification of bulk cemented carbides, some new powder metallurgical methods have been developed in recent years, including high frequency induction-heated sintering (HFIHS) [7], microwave sintering (MS) [8] and spark plasma sintering (SPS) [9], [10], [11], [12], [13]. Generally, the cemented tungsten carbides prepared by the new generation sintering methods were reported to have high hardness and good toughness [7], [8], [9], [10], [11], [12], [13], [14]. In addition, some routes have the advantages of the rapid consolidation and manufacturing of complex parts, such as selective laser melting [14], [15] and warm flaw compaction (WFM) [16]. Besides, considerable amount of investigations have been done about in-situ hardmetals recently [14], [15], [16], [17], [18], [19]. Some researches indicate that in-situ hardmetals are thermodynamically stable, leading to less degradation in elevated temperature applications. Furthermore, the present metal interfaces within in-situ hardmetals are generally cleaner and more compatible, yielding stronger interfacial bonding and elevated mechanical properties of the final products [20].

Consumable electrode D.C. arc in-situ metallurgy (CDISM) is a novel in-situ reactive synthesis technique, which uses the self-designed CDISM equipment as heat source to synthesize composite W_pC materials in the cavity of substrate. Currently, there are no publications addressing the W_pC composites prepared by CDISM. The route of CDISM is developed from the plasma in-situ metallurgical technique (PISM) [21]. The previous works indicate that composites couldn't be synthesized in the deep hole of the substrate by the PISM due to the large size of the plasma torch. In this study, the W_pC (WC + W₂C) composite materials were synthesized in the blind hole of the cutting pick, by using D.C. arc as heat source to melt consumable electrode in an in-situ metallurgy reaction manner between elements. Hard phases WC and W₂C were in-situ synthesized from high temperature melts via a liquid-phase reaction mechanism, possessing the advantages of uniform and compact of alloy structure, high wear resistance. Compared with the other newly developed routes, consumable electrode D.C. arc in-situ metallurgy technique exhibits more significant advantages, such as low cost, high efficiency and convenient operation. In this work, the consumable electrode D.C. arc in-situ metallurgy technique is employed to affect the microstructure characteristics and formation mechanisms of the composite W_pC. Developments of microstructure and microhardness are revealed and formation mechanisms are proposed.

Section snippets

Materials

42CrMo steel pick (produced by Jinhaina Plasma Tec. Co., Ltd. China) quenched and tempered was applied as the substrate whose chemical composition in wt.% is shown in Table 1. The specimen was one-time formed in a Ф20 × 30 mm blind hole drilled at the top of the pick.

99.9% purity tungsten powder (W) with an polyangular structure and an average particle size of 2.5 μm and pure greasy graphite powder (C) with a mean particle size of 30 μm were adopted as the starting powder materials and analytical

Microstructures

Fig. 3 illustrates the X-ray diffraction (XRD) analysis result of in-situ metallurgy samples. As shown in Fig. 3, the principal hard phases are WC, W₂C, η-Fe₃W₃C, Cr₇C₃, (Fe, Ni)₃C and γ-Fe. Fig. 4(a) presents the principal microstructure of the W_pC alloy and depicts that triangular and rectangular grains with the regular shape have a homogeneous distribution. The XRD analysis result shown in Fig. 3 and EDS analysis results in Fig. 5 reveal that the principal elements are W and C, though

Conclusions

In this work, an innovative rapid route for preparing W_pC composite materials has been introduced. Tungsten powder and graphite powder were used as the raw materials, by the in-situ reaction with short term procedures. Nearly fully dense W_pC composite is obtained in the blind hole of the cutting pick within 2 min.

1.
The principal hard phases of composite W_pC picks cutter are WC, W₂C, η-Fe₃W₃C, Cr₇C₃, (Fe, Ni)₃C and γ-Fe, the composite has excellent metallurgical bonding with the substrate.
2.
The

Acknowledgments

This research has been kindly supported by the Natural Science Foundation of Shandong Province, China (2009ZRB01417). The authors would like to acknowledge Jinhaina Plasma Tec. Co., Ltd. for providing research facilities.

References (27)

I.J. Shon et al.
Properties and rapid consolidation of ultra-hard tungsten carbide
J Alloys Compd
(2010)
I. Konyashin et al.
Near-nano WC-Co hardmetals: will they substitute conventional coarse-grained mining grades
Int J Refract Met Hard Mater
(2010)
S. Luyckx et al.
Increasing the abrasion resistance without decreasing the toughness of WC-Co of a wide range of compositions and grain sizes
Int J Refract Met Hard Mater
(2007)
I. Konyashin et al.
Novel ultra-coarse hardmetal grades with reinforced binder for mining and construction
Int J Refract Met Hard Mater
(2005)
R. Veinthal et al.
Characterization and prediction of abrasive wear of powder composite materials
Wear
(2009)
K. Matsuura et al.
Combustion synthesis of boride particle dispersed hard metal from elemental powders
Int J Refract Met Hard Mater
(2009)
T.E. Kim et al.
In situ martensitic phase reinforced Fe–Nb–Ni–Mn ultrafine composite with enhanced mechanical properties
Mater Sci Eng A
(2012)
D. Dmytro et al.
Initial stage sintering of binderless tungsten carbide powder under microwave radiation
Ceram Int
(2011)
J.X. Zhang et al.
Binder-free WC bulk synthesized by spark plasma sintering
J Alloys Compd
(2009)
C. Rachman
Densification mechanisms in spark plasma sintering of nanocrystalline ceramics
Mater Sci Eng A
(2007)

D. Sivaprahasam et al.

Microstructure and mechanical properties of nanocrystalline WC-12Co consolidated by spark plasma sintering

Int J Refract Met Hard Mater

(2007)

X.Q. Wang et al.

Sintering of WC-Co powder with nanocrystalline WC by spark plasma sintering

Rare Met

(2006)

X.L. Shi et al.

Mechanical properties, phases and microstructure of ultrafine hardmetals prepared by WC–6.29Co nanocrystalline composite powder

Mater Sci Eng A

(2005)

Cited by (21)

Surface modification of AISI 8620 steel by in-situ grown TiC particle using TIG arcing
2021, Surface and Coatings Technology
Citation Excerpt :
This is necessary in order to create a homogeneous distribution of fine particle along the top to bottom of the fused zone allowing formation of uniformly distributed fine reinforcement. The dispersoid formed during in-situ reinforcement is thermally stable, and leads to low deterioration in service at elevated temperatures [12]. Various kinds of reinforcements had been used in developing a composite layer on steel substrate.
In-situ grown titanium carbide (TiC) reinforced steel matrix was produced with tungsten inert gas (TIG) arcing by the metallurgical reaction between titanium and graphite powder on bearing steel (AISI 8620). Microstructure, chemical composition, and formation of TiC precipitate particles were thoroughly analysed primarily for basic understanding of transformation characteristics and morphology of the TiC particles as a function of the process parameters. The microstructure was analysed with the help of several tools like field emission scanning electron microscope (FESEM) equipped with energy dispersive spectroscopy (EDS), electron probe micro analyzer (EPMA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The treated surface was practically free from cracks and porosity. The modified surface consists of in-situ synthesized titanium carbide precipitate in the martensite matrix. The XRD results confirmed the presence of titanium carbide precipitate. The changes in TIG arcing parameters have been found to vary the dilution of the modified zone which has subsequently affected the concentration of TiC precipitates in the modified region. Considerable enhancement in the mechanical properties of the modified surface was examined using microhardness and wear test. The average hardness of the modified surface with flux of lowest current reached to about 2.15 times that of the base metal. The wear test reveals the effectiveness of the TiC precipitate with the enhancement in wear resistance of about 4.6 times that of as received sample. Surface modification of the substrate was also carried out by employing TIG arcing without the addition of the flux coating to make a comparative study on the evolution of microstructure and its effect on mechanical behavior to find out the utility of using the flux coating for an exclusive benefit of the surface modification for superior properties.
Characterization of iron-based surface multilayer-structured tungsten carbide composite layers by EBSD and FIB/TEM
2020, Surface and Coatings Technology
Citation Excerpt :
Clearly, the phase composition of microscopic interface obtained by TEM agrees well with the EBSD results (Fig. 3e). Additionally, the TEM characterization results are in agreement with previously reported studies [27–29], especially the lattice feature of Fe3W3C is similar to Co3W3C [28]. But, it notes that the W phase does not found in the III region, indicating that the only Fe3W3C phase is in the III region.
To strengthen the surface, tungsten carbide composite layers on an iron-based alloy were produced by a diffusion-controlled in-situ reaction in the solid state treated from 1000 °C to 1100 °C. Microstructure of the carbide layer was characterized by using electron backscatter diffraction (EBSD), focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. The results reveal that the composite carbide layers exhibit a multiple-layer structure and orderly consists of the thin W₂C layer and Fe₃W₃C layer, and a broad WC-Fe layer from top to bottom. Even then, the WC-Fe cemented layer dominates among them. The interface of the carbide layers/substrate is validated with an intimate metallurgical bond. Due to inadequate reaction, a thin tungsten plate covers the surface of the W₂C layer. A highly distorted W₂C lattice structure and an atomic transition layer with the thickness of about 6.79 nm were observed at the vicinity of the W/W₂C interface by high-resolution TEM. Additionally, the relationship of crystal orientation obtained between the WC and α-Fe is WC $[\bar{2} \bar{1} 2]$ //α-Fe $[11 \bar{2}]$ . EBSD characterization shows that the morphology of WC grains mainly presents the equiaxial and columnar. The orientation of WC grains indexed tends to $〈01 \bar{1} 0〉$ and $〈\bar{1} 2 \bar{1} 0〉$ crystalline directions as the elevated temperature. Furthermore, grains of solid solution Fe₃W₃C with a cubic structure have a columnar morphology, and the growth direction of columnar grain is perpendicular to the W₂C layer. The oriented growth of carbide grains can be attributed to the diffusion-controlled growth mechanism.
Improving wear resistance and friction stability of FeNi matrix coating by in-situ multi-carbide WC-TiC via PTA metallurgical reaction
2019, Surface and Coatings Technology
This paper presents a new type of FeNi matrix composite coating reinforced with multi-scale carbides WC-TiC fabricated by in-situ synthesis method PTAMR (plasma transferred arc metallurgical reaction). The microstructures, phases, hardness, and tribology properties of the composite coating were analyzed. Results show that the multi-scale carbides WC-TiC with fine intact shape were successfully in-situ synthesized in the matrix. Owing to the in-situ synthesis method, plenty of TiC tiny carbides in-situ grow in both the carbide WC and matrix, known as the precipitation hardening, by which the hardness of carbide WC and matrix are increased from 1497 to 1682 HV_4.9 and 411 to 731 HV_4.9 respectively. The analysis of crystallographic relationship shows that the lattice misfit between ${(10 \bar{1} 0)}_{WC}$ and (001)_TiC is 6.26%, indicating carbides WC and TiC can act as mutual effective heterogeneous nuclei and promote each other. Benefit from the in-situ WC-TiC multi-scale carbides hybrid growth characteristic, the wear resistance, and frictional stability are all increased in compared with the coating reinforced with in-situ single-carbide WC.
Microstructural evaluation and mechanical properties of in-situ WC/W-Cu composites fabricated by rGO/W-Cu spark plasma sintering reaction
2018, Materials and Design
In the current study, the reduced graphene oxide (rGO) was introduced into W-Cu composites for in-situ formation of WC particles using one-step thermal reduction and followed by spark plasma sintering reaction at 1050 °C for 10 min under a pressure of 80 MPa in a vacuum atmosphere. The microstructural characteristics, interface structure and mechanical properties of composite were investigated. The results exhibited that the GO flakes were effectively reduced to graphene in the rGO/W-Cu composites powders after reduction in hydrogen at 350 °C for 120 min. The relative density of rGO/W-Cu composites is higher than that of rGO-free composite that is attributed to the formation of some WC phases which can enhance the wettability between W and Cu in the sintering process. The formation of WC interlayer with thickness of about 8 nm at the W/Cu interface suggests that W and C atoms diffuse mutually and accumulate to form the carbides at the W-Cu interfaces in sintered rGO/W-Cu. The formation of WC at the interface can also enhance the interfacial bonding strength of W and Cu matrix. No evidence of W-Cu interfacial separation can be found in fracture surface, demonstrating positive effect of rGO on the interfacial strength of the composite.
Evaluation of microstructure and growth kinetics of tungsten carbide ceramics at the interface of iron and tungsten
2018, Journal of Alloys and Compounds
Citation Excerpt :
Iron-based composites with tungsten carbide ceramics as the reinforcements have been widely investigated due to their high stiffness, high strength, and improved resistance to creep, fatigue and wear [1–4].
The microstructure evolution and growth kinetics of tungsten carbide (WC or W₂C) ceramics at the interface of iron and tungsten during isothermal annealing process from 1100 °C to 1150 °C were investigated by X-ray diffraction (XRD), electron backscattered diffraction (EBSD) and scanning electron microscopy (SEM), respectively. The results show that carbide formation that involves W₂C, WC and a small quantity of Fe₂W₂C, is strongly dependent on a diffusion-controlled reaction. During the evolution process of tungsten carbides, W₂C emerges as an initial phase by the reaction of W and C, and WC is formed as the second phase, because the value of Gibbs free energy of formation of W₂C is more negative than that of WC at the annealing temperature. The initial W₂C transforms into WC until complete consumption of the W₂C. Additionally, Fe₂W₂C between W₂C and WC was formed at a relatively low temperature (1100 °C and 1125 °C) with a long annealing time (60 min). After the W₂C is consumed completely, WC grows by C diffusion, where the growth kinetics of a dominant WC ceramic exhibits a parabolic growth law before metal tungsten is completely consumed. The growth activation energy of the WC layer is calculated to be achieved with a value of 208.68 kJ/mol. When the metal tungsten is completely consumed after annealing at 1150 °C for 60 min, the W₂C and Fe₂W₂C disappear, and only the WC phase exists in the final product.
Microstructure and tribology behaviors of in-situ WC/Fe carbide coating fabricated by plasma transferred arc metallurgic reaction
2017, Applied Surface Science
Citation Excerpt :
Therefore, WC is extensively used as reinforcements in metal matrix composites, such as Co, Ni, Fe, Cu or Al to improve the mechanical properties, including wear, oxidation and corrosion resistance, to produce tools for machining, ammunition, mining, nuclear, sports, surgical instruments, jewelry and others [1,3]. Previously, many conventional methods are employed to fabricate the composites, for instance, the vacuum sintering [4], spark plasma sintering (SPS) [5], hot isostatic pressing sintering (sinter-HIP) [6], plasma spraying [7], cold spraying [8,9], centrifugal casting [3], self-propagating high-temperature synthesis (SHS) [10], selective laser melting [2], laser cladding [1,11], consumable electrode D.C. arc in-situ metallurgy (CDISM) [12], and plasma transferred arc welding (PTAW) [13]. It can be found that among these techniques, two kinds of methods have been used to obtain the reinforcements, one is ex-situ method and the other is in-situ method.
In order to improve the dry sliding tribology properties of mild steel compound, the in-situ WC carbide coatings with 18, 32, 54 vol% WC were successfully synthesized using plasma transferred arc metallurgic reaction (PTAMR) with alloy powders W, C and Fe-30Ni. The composition, microstructure and microhardness of the carbide coatings were characterized. It was found that the carbide coating consisted of WC, M₆C and γ phases, carbides distribute gradually from the coating bottom to top, the in-situ WC crystal grows into triangle prism structure with high hardness and good toughness. Dry sliding tribology behaviors were studied on block-on-wheel dry sliding wear tester with load 300 N, sliding speed 0.836 m/s and distance 500 m. Results show that the friction coefficient diagrams contain three stages, variation of friction coefficient increase with the content of WC, friction temperature increase with the sliding distance, increasing the content of WC can directly increase the antiwear property of WC/Fe carbide coating. The main wear mechanisms of in-situ WC/Fe carbide coating are adhesive, oxidation, micro-cutting and ploughing wear.

View all citing articles on Scopus

View full text

Applications of WC-based composites rapid synthesized by consumable electrode in-situ metallurgy to cutting pick

Abstract

Highlights

Introduction

Section snippets

Materials

Microstructures

Conclusions

Acknowledgments

Properties and rapid consolidation of ultra-hard tungsten carbide

J Alloys Compd

Near-nano WC-Co hardmetals: will they substitute conventional coarse-grained mining grades

Int J Refract Met Hard Mater

Increasing the abrasion resistance without decreasing the toughness of WC-Co of a wide range of compositions and grain sizes

Int J Refract Met Hard Mater

Novel ultra-coarse hardmetal grades with reinforced binder for mining and construction

Int J Refract Met Hard Mater

Characterization and prediction of abrasive wear of powder composite materials

Wear

Combustion synthesis of boride particle dispersed hard metal from elemental powders

Int J Refract Met Hard Mater

In situ martensitic phase reinforced Fe–Nb–Ni–Mn ultrafine composite with enhanced mechanical properties

Mater Sci Eng A

Initial stage sintering of binderless tungsten carbide powder under microwave radiation

Ceram Int

Binder-free WC bulk synthesized by spark plasma sintering

J Alloys Compd

Densification mechanisms in spark plasma sintering of nanocrystalline ceramics

Mater Sci Eng A

Microstructure and mechanical properties of nanocrystalline WC-12Co consolidated by spark plasma sintering

Int J Refract Met Hard Mater

Sintering of WC-Co powder with nanocrystalline WC by spark plasma sintering

Rare Met

Mechanical properties, phases and microstructure of ultrafine hardmetals prepared by WC–6.29Co nanocrystalline composite powder

Mater Sci Eng A