Chinese Journal of Aeronautics, (2014),27(4): 1022–1029

Chinese Society of Aeronautics and Astronautics& Beihang University

Chinese Journal of Aeronautics

cja@buaa.edu.cnwww.sciencedirect.com

Grinding performance evaluation of porouscomposite-bonded CBN wheels for Inconel 718

* Corresponding author. Tel.: +86 25 84896511.

E-mail address: jhxu@nuaa.edu.cn (X. Jiuhua).

Peer review under responsibility of Editorial Committee of CJA.

Production and hosting by Elsevier

http://dx.doi.org/10.1016/j.cja.2014.03.0151000-9361 ª 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA. Open access under CC BY-NC-ND license.

Chen Zhenzhen, Xu Jiuhua *, Ding Wenfeng, Ma Changyu

College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, ChinaJiangsu Key Laboratory of Precision and Micro-Manufacturing Technology, Nanjing 210016, China

Received 11 September 2013; revised 20 November 2013; accepted 10 December 2013Available online 17 March 2014

KEYWORDS

Alumina bubbles;

Bending strength;

Cubic boron nitride (CBN);

Porosity;

Specific force;

Specific grinding energy

Abstract For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel

alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function.

However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore

forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic

boron nitride (CBN) wheels. When the wheel porosity reaches 45%, the bending strength is still

high up to 50 MPa with modified orderly pore distribution. A porous CBN wheel was fabricated

with a total porosity around 30%. The grinding performance of the porous composite-bonded

CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temper-

ature, which were better than those of the vitrified one under the same grinding conditions. Com-

pared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed

on the ground surface and there is also no extensive loading on the wheel surface after grinding.ª 2014 Production and hosting by Elsevier Ltd. on behalf of CSAA & BUAA.Open access under CC BY-NC-ND license.

1. Introduction

Superalloys are often used as the material for turbine blades

and jet engines of airplanes that requires high performanceat elevated temperature. Nickel-based alloys are the mostwidely used superalloy, accounting for about 50% of thematerials used in aerospace engines, mainly in the gas turbine

compartment.1 They have low heat conductivity and high

strength, which make it very difficult to obtain effectivegrinding processes with high accuracy.2–4 Depending on theexcellent properties of cubic boron nitride (CBN) abrasive

grains such as high hardness, high thermal conductivity, andhigh wear resistance, CBN tools are widely applied to machinemany materials,5–7 especially having advantages to machine

difficult-to-cut materials such as titanium alloy and nickelsuperalloy.8–11

When conventional and vitrified-bonded CBN grinding

wheels are used for grinding nickel-based alloys, the greatamount of wheel wear greatly affects the efficiency of a grind-ing process.9,10 Frequent wheel dressing and a large dressingdepth to clean up the wheel surface are needed due to wheel

loading. Wheel redressing caused by wheel loading is a maincause of giant wheel wear and must be prevented. Hasudaet al.12 used metal-bonded CBN wheels for grinding

http://crossmark.crossref.org/dialog/?doi=10.1016/j.cja.2014.03.015&domain=pdfmailto:jhxu@nuaa.edu.cnhttp://dx.doi.org/10.1016/j.cja.2014.03.015http://dx.doi.org/10.1016/j.cja.2014.03.015http://www.sciencedirect.com/science/journal/10009361http://dx.doi.org/10.1016/j.cja.2014.03.015http://creativecommons.org/licenses/by-nc-nd/4.0/http://creativecommons.org/licenses/by-nc-nd/4.0/

Fig. 1 Stress distribution in block.

Fig. 2 Influence of pore size on maximum stress.

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718 1023

superalloys, and high grinding ratio and stable surface rough-ness were obtained. However, for high-efficiency grinding ofsuperalloys such as Inconel 718, high wheel porosity is neces-

sary for large chip-storage space, good cooling effect, andgood self-dressing ability.13,14 In addition, the metallic bondcreates problems with profiling and sharping due to the high

mechanical strength.Therefore, porous metal-bonded super-abrasive grinding

wheels are considered as a new solution, which have a good

combination between abrasive grains and bonding materials,large chip-storage space, high grinding ratio, and gooddressing ability. In the past decade, pore forming agent mate-rials,15–19 e.g., NH4HCO3, CaCO3, TiH2, have been used to

create open-structure pores and high wheel permeability. Aproblem is that the high induced porosity, totally providedby the sacrificial organic material, does not have sufficient

physical strength to function satisfactorily. As well known,wheel porosity and wheel wear are a contradiction. Moreover,the pore shape and size inside a wheel are not identical, which

affects the uniformity of the wheel structure.To overcome the problem mentioned above, alumina

(Al2O3) bubble particles (or called bubbled alumina)20 are

involved as a pore-forming agent to create closed pores insidea wheel and open pores on the wheel surface. The pore struc-ture including pore shape, pore size, and pore distributioncould be controlled. At the same time, the appropriate

mechanical strength of composite blocks could be adjustedby adding different amounts of pore-forming agents to meetthe requirements of grinding wheels. In addition, good bond-

ing among Cu–Sn–Ti alloy/CBN grits could be obtained basedon the brazing reaction at a vacuum atmosphere. So far, por-ous composite-bonded CBN grinding wheels may be prepared.

Bubbled alumina is a weak thin-walled hollow sphere of alu-mina having an average diameter of generally 0.2–5 mm. Thewall thickness is usually in the order of 20–40 lm. Such materi-als are commercially available from many companies. The sizeof the alumina bubbles which are usedwill preferably vary basedupon the coarseness of the abrasive grits used for a wheel.21 Inview of the used CBN grit size of 80/100 mesh, the bubble size

of 0.2–1.0 mm is introduced in the present investigation.Firstly, the influence of pore size on stress is discussed

based on FEM simulation results and a template with a mod-

ified pore distribution pattern is machined to improve the poreuniformity in the blocks. Subsequently, porous CBN compos-ite blocks are prepared and flexural strength is measured. Then

a porous composite-bonded CBN wheel is fabricated. Finally,a preliminary comprehensive evaluation of high-speed grind-ing performances of the developed wheel and a vitrified oneis made in terms of specific force, specific grinding energy,

grinding temperature, ground surface, and wheel topography.

2. Fabrication of porous CBN wheels with pore-forming agent:

alumina bubbles

2.1. Influence of pore size on maximum stress based on FEMsimulation

To obtain a suitable range of Al2O3 bubble size for wheel

fabrication, the relationship between pore size and stress wasfirstly studied based on FEM simulation. A 3D model, a2 mm · 2 mm · 2 mm cubic block with pores, was applied in

simulation. The pore size was from 0 to 1 mm. ABAQUS 6.9was used for simulation. It is supposed that the isotropic mate-rial and steady-state conditions are fulfilled. The elasticity mod-

ule E is 700 GPa and Poisson ratio l is 0.3. The element type ofFEMmesh is tetrahedral. In case of pore size of 0.5 mm under atransverse tensile load p, the simulation result of von Mises

stress distribution in the block is shown in Fig. 1, in which‘‘von Mises’’ is the abbreviation of von Mises stress. The max-imum stress appears on the boundaries of the pores. Simulation

tests were conducted with series of pore sizes and the variationsof maximum stress with pore size are shown in Fig. 2.

For porous composite materials, the fracture occurs in theweakest cross-section and the stress r is described by22

r ¼ PAm

ð1Þ

where P is the load per square and Am is the effective area persquare in the weakest cross-section. For the spherical poremodel, Am is solved by

Am ¼ 1� pr2 ð2Þ

where r is the radius of the spherical pore. Combining Eq. (1)and Eq. (2), the stress r is given by

r ¼ P1� pr2 ð3Þ

In a conclusion, whenP is constant, with increasing pore size,the stress in the weakest section increases following this function.

Table 1 Proportion of Alumina by weight and volume.

Alumina bubbles Sample No.

1 2 3 4 5 6

wt% 0 5 10 15 20 25

1024 Z. Chen et al.

As shown in Fig. 2, the simulated stress trend is in agree-ment with this function quite well. In general, with increasedpore size, the maximum stress in the block increases. When

the pore size is increased from 0 to 1 mm, the stress is variedfrom 0.88 to 2.31 GPa. However, when the pore size is smallerthan 0.7 mm, the influence of pore size on stress is little. When

the pore size is larger than 0.7 mm, it turns out that the influ-ence becomes greater. Therefore, according to the grit size usedfor the wheel, alumina (Al2O3) bubbles with a diameter around

0.5 mm are chosen for this investigation.

2.2. Modified pore distribution pattern in composite blocks

Composite blocks were manufactured using the mixture ofCu–Sn–Ti alloy powder (binder), CBN grits (abrasive), graph-ite particles (pore former and also solid lubricant), andalumina bubbles (closed pore forming agent). The manufac-

ture process of composite blocks was similar to what wasreported in the corresponding literature.20 The difference isthat, to prevent the bubbles gathering on the top of mould

and improve the pore uniformity in the blocks, the aluminabubbles are orderly arranged by templates. The compositeblocks with original and modified pore patterns are demon-

strated in Fig. 3(a) and (b), respectively. On the basis of the0.5 mm diameter of alumina bubbles, the holes in templatesare machined with a diameter of 0.6 mm for fabricating com-posite blocks in Fig. 3(b). Compared to the pore distribution

achieved before, pore continuity is improved during wheelwear with the preferred pore size.

2.3. Variation of bending strength with volume of aluminabubbles

For porous metal-bonded grinding wheels, the wheel porosity

is mainly made of closed pores due to the pore former, bubbledalumina, and open pores being the natural or residual porosityof the wheel. It is confusing to put the porosity and the closed

pores volume together. In this paper, the closed pores volumewill be concerned.

A mixture was made of 20 parts 80/100 grit CBN abrasives,0–25 parts alumina bubbles (0.5 mm in diameter) and balance

parts a composite bond composition of CuSnTi alloy andgraphite particles with a normal size of under 100 lm. The

Fig. 3 Composite blocks with different pore patterns.

mixture was cold pressed in a mould to obtain compositeblocks. Subsequently, the blocks were sintered in a vacuumfurnace and cooled down. At this point, the samples (sintered

blocks) were prepared. Table 1 lists the proportion of aluminabubbles by weight in the mixture and relatively by volume inthe sintered blocks. When the alumina bubbles are added

25 wt% into the mixture, the closed pores volume reachesaround 47 vol% in the sintered blocks. This is the total volumeof the alumina bubbles, because most of the bubbles in the

wheel working surface would be extracted under the highwheel rotational speed.

Transverse rupture strength (TRS),23 also known as flex-ural strength or bending strength, measured by the 3-point

bend test method, is one of the most frequently tested mechan-ical properties of sintered metal materials. The reason is thatTRS is extremely sensitive to levels of porosities and inhomo-

geneities. Fig. 4 shows the bending strength of the sampleswith disorderly and orderly pores.

In general, the pores volume increase is disadvantageous to

the bending strength under both situations. For the blockswith disorderly pores, when the volume is changed from 0 to47 vol%, the strength is varied from 123 to 48 MPa. However,

the bending strength of these sintered blocks is still higher thanthat of the traditional vitrified wheels with a porosity of 30%.This phenomenon proves the good combination at the inter-faces of Cu–Sn–Ti alloy/CBN grains obtained at the sintering

temperature of 880 �C.Clearly seen from Fig. 4 is that, for the blocks with orderly

pores, the bending strength is slightly higher than that with

disorderly pores. The benefit of orderly distribution of porescan be explained from Fig. 5, which displays the orderly anddisorderly pore distributions in blocks with the same porosity.

Due to limitations of mechanical mixing technique, sampleswithout an orderly pore distribution lead to an inhomogeneousdistribution of pores in the block, as shown in Fig. 5(b), in

which pore segregation phenomenon is found in partial areaI. This inhomogeneous distribution of pores leads to a smaller

Fig. 4 Variation of bending strength with closed pores volume.

vol% 0 10 21 30 39 47

Fig. 5 Schematic of pore distribution.

Fig. 6 Wheel flank side morphology after truing.

Fig. 7 Working surface morphology after dressing.

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718 1025

effective area Am in area I. Incorporated with Eq. (1), the stressturns to be higher, that’s to say, a composite block with a dis-

orderly pore distribution is fragile by the same loading force.Considering the chip-storage space and bending strength,

the preferred amount of alumina bubbles is generally about25 vol%–35 vol% of the grinding product. Approximately

70 vol% of the bulk volume of the bubbled alumina is porosityin the product. In the present investigation, a porous compos-ite-bonded CBN grinding wheel is fabricated with the total

porosity above 30%. That is, the corresponding weight contentof the alumina bubbles is 15 wt%.

2.4. Fabrication of the porous composite-bonded CBN wheel

The grinding wheel includes two parts: the wheel substrate andthe abrasive layer. The wheel substrate is made of carbon steel

(AISI 1045), harden and tempered. The diameter of the sub-strate is 388 mm. The wheel abrasive layer, which consists of32 composite blocks, is manufactured using the improved porepattern with the same processing method above. Afterwards,

the wheel substrate and the composite blocks after surfacetreatment were bonded using epoxy resin adhesive and driedin an oven with a temperature of 180 �C for 45 min. Accord-ingly, the porous composite-bonded CBN grinding wheel witha size of 400 mm · 10 mm · 127 mm was fabricated, and theconcentration of the grinding wheel is 100. Thus, the specifica-

tion of the developed wheel is named as B181C100.

3. Grinding performance of porous CBN grinding wheel forInconel 718

3.1. Conditioning of grinding wheel

Truing and dressing must be performed before grinding.24,25

The purpose of truing is to achieve a considerable profile by

removing the extra adhesive and decreasing the wheel facerun-out. The purpose of dressing is to sharpen the grindingwheel by removing the bonding material around the CBN grits

and breaking the alumina bubble particles to obtain the chipstorage space.

The truing and dressing of the wheel are respectively con-

ducted on an M1432A external cylindrical grinding machineand a BLOHM Profimat MT408 surface machine. The wheelwas trued by cylindrical grinding with a sintered diamond

wheel. Fig. 6 shows the morphology of the wheel flank sideafter truing. The pore shape is kept nearly complete, whilethe pore size is decreased to a certain extent due to thecompressing in the press mould before sintering. Moreover,

compared with the template used in Fig. 3(b), the pore distri-bution pattern is almost the same. In this stage, the CBN gritsare still embedded in the bond. Afterwards, the wheel was

dressed at a depth of cut of 0.1 mm with a stick-type dressingstone. The plunge grinding type was carried out. After dress-ing, it can be found that the CBN grits on the working surface

are exposed, as shown in Fig. 7. The orderly pores are alsoexposed completely after dressing.

The grinding experiments were conducted on a typical

nickel-based superalloy, Inconel 718. The width of the work-piece is 5 mm. The grinding parameters are summarized inTable 2. Meanwhile, a vitrified CBN wheel (B181V100) hasbeen applied for comparing the grinding performance with

the porous CBN wheel.To evaluate the grinding performance of the porous CBN

wheel, the grinding force components (tangential force, normal

force) are measured using a piezoelectric transducer-based typedynamometer (Kistler 9272), coupled to charge amplifiers anda PC running Dynowear software. The grinding temperature is

Table 2 Grinding parameters.

Parameter Values

Wheel velocity vs (m/s) 50, 60, 70, 80, 90

Infeed speed vw (mm/min) 640–9600

Depth of cut ap (lm) 10, 15, 20, 25, 30

1026 Z. Chen et al.

measured based on semi-artificial thermocouple technology.The ground surface and wheel surface topography after grind-ing are observed by a digital microscope (HIROX KH-7700).

3.2. Specific forces

There are many factors affecting grinding forces, such as wheel

condition, cooling fluid, wheel wear, and grinding parameters.Based on the same grinding conditions, it is necessary to showthe relationship between grinding forces and grinding parame-

ters. Usually, specific force F 0 is analyzed, which is the grindingforce divided by the ground width. Fig. 8 illustrates the specificnormal force Fn

0 and the specific tangential force Ft0 of both the

porous CBN wheel and the vitrified counterpart.As seen from Fig. 8, for both wheels, the specific forces

generally decrease with increasing wheel speed and increasewith increasing depth of cut. For example, as seen from

Fig. 8(b), when the depth of cut increases from 10 to 30 lm,the specific normal forces Fn

0 of the vitrified CBN wheel andthe porous one have been raised from 8 to 34 N/mm and from

Fig. 8 Specific forces versus grinding parameters.

6.6 to 16.8 N/mm, respectively. This is attributed to the factthat the increase in depth of cut results in the increase in theundeformed chip thickness. What is more remarkable is that

the specific forces of the porous CBN wheel are lower thanthose of the vitrified one, especially the specific normal forceFn0 nearly 30% lower under the same material removal. How-

ever, the specific tangential forces Ft0 are less sensitive for both

grinding wheels with various wheel speeds.The grinding force ratio of the porous CBN wheel is much

lower than that of the vitrified one, which means the former ismuch sharper. Due to the pore-forming effects of aluminabubbles, the chip and coolant storage space is larger, andbased on the graphite lubricating, rubbing between the grind-

ing wheel and the workpiece in the grinding contact zone isweakened, which makes the wheel less adhesive and CBN gritssharper. These all imply that the porous CBN wheel is more

suitable than the vitrified one for grinding Inconel 718.

3.3. Specific grinding energy

Specific grinding energy es (J/mm3), which is defined as the

energy expended per unit volume of material removal, isanother important grindability index. It can be calculated with

the grinding parameters and the measured tangential grindingforce Ft as follows

26:

es ¼60Ftms

1000mwapbð4Þ

where b (mm) is the width of the working zone of the grindingwheel, i.e., 5 mm in present experiments.

Generally, the specific grinding energy is studied in terms of

the maximum undeformed chip thickness hcumax. Based on thegeometrical characteristics of the chip formation, hcumax iswritten as26

hcumax ¼4mw

msNdC

ffiffiffiffiffiapds

r� �1=2ð5Þ

where Nd is the active cutting point density (8 mm�2 in this

work); C is a constant correlated with the angle of the grainh (C= 4tanh, where h is 30� for the grit size of 80/100 mesh),which is taken to be 6.928; ds is the diameter of the grindingwheel (400 mm).

The specific grinding energy for high-speed grinding(vs = 80 m/s) of Inconel 718 is plotted against the maximum

undeformed chip thickness in Fig. 9. With the application ofthe least squares curve-fitting technique to the experimentaldata, the specific grinding energy of the vitrified CBN wheel

rs-vitrified and the specific grinding energy of the developed por-ous CBN wheel rs-porous are respectively represented by:

rs-vitrified ¼ 82:44h�1:1997cumax ð6Þ

rs-porous ¼ 67:07h�1:22cumax ð7Þ

As seen from Fig. 9, the specific grinding energy of Inconel718 is up to 100–500 J/mm3, which implies that the grindabilityof this material is real bad. It can also be seen from Fig. 9 that

the specific grinding energy of Inconel 718 with the porousCBN wheel is lower than that with the vitrified one. Thisimplies that the grinding performance of Inconel 718 usingthe porous CBN wheel is better than that using the vitrified

one in these cases. This is mainly attributed to the large pores

Fig. 9 Specific grinding energy versus undeformed chip

thickness.

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718 1027

and sharp cutting edges on the wheel surface, which require

less energy to remove the material and avoid the chipadheison.

With increasing undeformed chip thickness, the specificgrinding energy is gernerally decreased. This can be explained

by the ‘‘size effect’’ of grinding wheels from the viewpoint ofthe abrasive-workpiece interaction.27 In the case of a smallhcumax, sliding and ploughing are the major behaviors during

grinding, which energy contributes to high specific grindingenergy. When hcumax is increased, the energy percentage fromsliding and ploughing decreases and consequently the specific

grinding energy decreases as well.

3.4. Influence of grinding parameters on grinding temperatures

Fig. 10 shows the typical temperature signal collected duringgrinding with the vitrified CBN wheel in grinding conditionof vs = 80 m/s, vw = 2000 mm/min, and ap = 10 lm. Thepeak values of the signal curve represent the temperatures of

the individual CBN grit participating in cutting, while thevalley values stand for the temperatures raised on the work-piece ground surface during grinding. In this study, the grind-

Fig. 10 Typical temperature signal (vw = 2000 mm/min,

ap = 10 lm, vs = 80 m/s).

ing temperature is the temperature increased on the workpiecesurface measured in the grinding contact zone. The tempera-ture at given condition is approximately 170 �C. The grindingtemperatures varying with the grinding wheel speed and thedepth of cut are plotted in Fig. 11(a) and (b), respectively.

As seen from Fig. 11(a), for the vitrified wheel, the grinding

temperature is generally increased with increasing wheel speed.This is attributed to that the more abrasive grits cutting pertime, the more friction leads to more heat generation. How-

ever, for the porous CBN wheel, in the case of wheel speedsof 80 and 90 m/s, the temperatures are decreased slightly.The proper explanation of this phenomenon is that the coolingeffect plays a more important role against the slight tempera-

ture rising with increasing wheel speed. It should be verifiedin further study. Increasing the depth of cut has the samebut more intense influence on raising grinding temperatures,

as shown in Fig. 11(b).It must be noticed that there is no doubt that the grinding

temperatures of the porous composite-bonded CBN wheel are

nearly 25% lower than those of the vitrified one in the presentinvestigation. The favorable advantage of the porous compos-ite-bonded CBN wheel can be mainly explained by the follow-

ing reasons, e.g., efficient chip storage space of the tools, betterthermal conductivity property of the bonding layer of Cu–Sn–Ti alloy than the vitrified bonding material, and less frictionbetween the binder and the ground surface because of the

self-lubricating effect of graphite particles added into the

Fig. 11 Influence of grinding parameters on temperature.

Fig. 13 Wheel surface topography with porous and vitrified

CBN wheel.

1028 Z. Chen et al.

bonding material.

3.5. Ground surface and wheel surface morphology after grinding

Fig. 12 displays the surface morphology of the workpieceground under the condition of vs = 80 m/s, vw = 2000 mm/min, and ap = 20 lm. Here, the surface roughness Ra isaround 0.4 lm. The cutting paths are observed on both groundsurfaces. Compared to the clear cutting paths with the porousCBN wheel, some flaws are found on the ground surface with

the vitrified CBN wheel, as shown in Fig. 12(b), as well asadhesive chips, ground chips, and proper wheel compositionparticles.

The quality of ground surface can reflect the condition ofa grinding wheel. Fig. 13 shows the wheel surface morphol-ogies of the porous CBN wheel and the vitrified counterpartafter grinding. Comparing these two figures, the number of

effective dynamic abrasives in Fig. 13(a) is less than that inFig. 13(b). Fewer cutting abrasives explain lower grindingforces. Attrition wear is found on both wheels, while exten-

sive adherence and blockage are only observed on the sur-face of the vitrified wheel. Grinding debris adheres to thesurface of the vitrified wheel and makes it blunt, which

attributes to the higher grinding temperatures. The wearmechanism of porous CBN wheels will be further reported.Above all, that’s to say, the porous composite-based CBNwheels have a promising application in grinding nickel-based

alloy.

Fig. 12 Ground surface morphology with porous and vitrified

CBN wheel.

4. Conclusions

(1) Alumina bubbles with a diameter of 0.5 mm are chosenconsidering the grit size of 80/100.

(2) The pore distribution pattern in blocks is modified, andthe bending strength of blocks with orderly pores isslightly higher than that with disorderly pores.

(3) A porous composite-bonded CBN wheel is fabricatedwith a bending strength around 60 MPa and porosityabove 30%.

(4) The specific grinding forces, specific grinding energy,and grinding temperatures of the porous composite-bonded CBN wheel are lower than those of the vitrifiedone in this investigation.

(5) Clear straight cutting grooves of ground surface areachieved by using the porous CBN wheel, while groundsurface with some flaws and severe adherence on the

wheel surface are found when using the vitrified one.

Acknowledgements

This study was co-supported by the Natural Science Founda-

tion of China (No. 51235004), Priority Academic ProgramDevelopment of Jiangsu Higher Education Institutions(PAPD) of China, the Fundamental Research Funds for the

Central Universities: Funding for Outstanding Doctoral Dis-sertation of China (No. BCXJ10-08), Funding for JiangsuInnovation Program for Graduate Education of China (No.CX10B-090Z-05), and Foundation of Graduate Innovation

Center at NUAA of China (No. kfjj130120).

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718 1029

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26. Ding WF, Xu JH, Chen ZZ, Su HH, Fu YC. Grindability and

surface integrity of cast nickel-based superalloy in creep feed

grinding with brazed CBN abrasive wheels. Chin J Aeronaut

2010;23(4):501–10.

27. Sin H, Saka N, Suh NP. Abrasive wear mechanisms and the grit

size effect. Wear 1979;55(1):163–90.

Chen Zhenzhen is a Ph.D. candidate at Nanjing University of Aero-

nautics & Astronautics (NUAA). She received her M.S. degree from

NUAA in 2006. Her research interests include fabrication of CBN

superabrasive grinding wheels and high-efficiency grinding technology

for difficult-to-cut materials.

Xu Jiuhua is a professor and Ph.D. advisor in the College of

Mechanical and Electrical Engineering at Nanjing University of

Aeronautics & Astronautics. His research interests are fabrication of

diamond and CBN superabrasive tools, green manufacture, and

machining technology for difficult-to-cut materials.

Ding Wenfeng is a professor and Ph.D. advisor at Nanjing University

of Aeronautics & Astronautics. He received his Ph.D. degree in

Mechanical Engineering at NUAA in 2006. His main research interests

are fabrication of superabrasive tools and high-efficiency grinding

technology for difficult-to-cut materials.

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Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 7181 Introduction2 Fabrication of porous CBN wheels with pore-forming agent: alumina bubbles2.1 Influence of pore size on maximum stress based on FEM simulation2.2 Modified pore distribution pattern in composite blocks2.3 Variation of bending strength with volume of alumina bubbles2.4 Fabrication of the porous composite-bonded CBN wheel

3 Grinding performance of porous CBN grinding wheel for Inconel 7183.1 Conditioning of grinding wheel3.2 Specific forces3.3 Specific grinding energy3.4 Influence of grinding parameters on grinding temperatures3.5 Ground surface and wheel surface morphology after grinding

4 ConclusionsAcknowledgementsReferences