Full Length Article
Surface integrity analysis in turning A03190/304 composites with
network reinforcement
Yang Qiao, Ning Fan, Peiquan Guo
⇑, Yang Bai, Shouren Wang
School of Mechanical Engineering, University of Jinan, Shandong 250022, China
a r t i c l e i n f o
Article history:Received 2 June 2016 Revised 27 July 2016 Accepted 27 July 2016 Available online 18 August 2016 Keywords: Composites Network reinforcement Surface roughness Surface integrity Turning
a b s t r a c t
A03190/304 composite specimen with network reinforcement has been prepared by means of metal die casting. Turning experiments and analysis of roughness and integrity of machined surface on A03190/304 composite specimen have been done with single-factor experimental method. Experimental results show that machined surface roughness decreases with the increasing of cutting speed, increases with the increasing of feeding rate. Machined surface roughness changes slightly as the variation of cutting depth within the value range of workshop operation. The investigation of integrity shows machined surface defects happened sometimes such as the attachment or insert of chip and its scratching, crack between matrix and reinforcement, stripping of reinforcement, bump of reinforcement, tearing of matrix and micro cracks of matrix. Experiment results show that machined surface defects can be controlled by means of decreasing feeding rate and cutting depth or increasing cutting speed.
Ó 2016 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
Metal matrix composites made of Aluminum alloy reinforced with particles, whiskers or wires as well as network structures are widely used in industry and engineering because of their excel-lent performances such as lightweight, low temperature tolerance, exceptional corrosion resistance, good plasticity, etc. [1–4]. The primary applications of these kinds of composites are for aero-space, defense, and automobile industries[5,6]. When composites are used in a product, characteristics of the surface generated sig-nificantly influence the product performance[7]. These materials are known as the difficult-to-machine materials, because of the hardness and abrasive nature of reinforcement element. The machined surface quality can be defined by means of two terms, that is, surface roughness and surface integrity. Some investiga-tions on the machining of metal matrix composites have been reported. Some of them are about machinability of Aluminum matrix alloy, such as cutting force, surface roughness [8–10]. Others are about the characteristics of machined surface quality
[11,12]. Chinmaya R. Dandekar [13] provides a comprehensive review of literature, mostly of the last 10–15 years, on modeling of machining of composite materials with a focus on the process of turning. Biswajit Das [14] fabricated an in-situ multi-component reinforced aluminum copper alloy based metal matrix
composite by the flux assisted synthesis (FAS) technique, and made an attempt to find out the most optimal level of process parame-ters for CNC milling of Al–4.5%Cu–TiC metal matrix composites using gray-fuzzy algorithm[15]. Gangadharudu Talla[16] made an attempt to fabricate and machine aluminum/alumina MMC using EDM by adding aluminum powder in kerosene dielectric, and results showed an increase in MRR and decrease in surface roughness (Ra) compared to those for conventional EDM. Surface roughness (Ra) is one of the most important factors for evaluating surface quality during the machining process, the quality of surface affects the functional characteristics of the workpiece[17]. Fur-thermore, surface roughness is among the most critical constraints in cutting parameter selection in manufacturing process planning. A03190/304 composites are a kind of metal (Aluminum alloy A03190) matrix composites which is enhanced by network struc-ture reinforcement (stainless steel 304). It is characterized by low apparent density, high strength and good stability relative to the single phase material. However, lack of research on the charac-teristics of machined surface about metal matrix composites with network reinforcement is blocking their application [3]. Some machining experiments have been done in order to investigate the roughness and integrity of machined surface as turning A03190/304 composites.
2. A03190/304 composites with network reinforcement The reinforcement material 304 is one of the most common nickel–chromium stainless steel with good mechanical properties. http://dx.doi.org/10.1016/j.jestch.2016.07.017
2215-0986/Ó 2016 Karabuk University. Publishing services by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
⇑Corresponding author.
E-mail address:[email protected](P. Guo). Peer review under responsibility of Karabuk University.
Contents lists available atScienceDirect
Engineering Science and Technology,
an International Journal
Network reinforcement made of 304 wires with 1 mm diameter as illustrated inFig. 1(a) is composed of cylindrical element, radial element and axial element. The preparation of Aluminum alloy A03190 matrix composite specimen which is shown inFig. 1(b) has been finished by means of natural casting with metal die. The composite specimen is a cylinder with 50 mm diameter and 110 mm length. Reinforcing phase 304 is of 20% fraction in volume. In order to ensure the specimen quality, the casting parts should be processed in furnace cooling and oven heat preservation. The mechanical properties of the matrix and reinforcement are shown inTable 1.
3. Experiment results and discussion 3.1. Planning of experiment
The experiments have been done by means of C616-1 lathe, PSSBR2020H13 tool holder and SNMM130504 –YG8 carbide insert,
as shown inFig. 2. During the whole course of the tests, the wear of tool was slight. So, the experimental investigation was focused on surface roughness and surface integrity. The influence of turning parameters on the surface topography was investigated with single-factor experimental method. Cutting parameters are shown inTable 2.
3.2. Roughness of machined surface on A03190/304 composites Surface roughness is one of the most important parameters to evaluate the machinability of material or quality of machined sur-face[17]. The cutting process of turning A03190/304 composites with network reinforcement is much more complex than that of turning conventional metal. There exist uncertainty and variety of machined surface during A03190/304 composites turned pro-cess. So, it is very important to evaluate the surface roughness comprehensively. Roughness can not only directly reflect the geo-metrical topography of machined surface, but also intuitively investigate the influence of reinforcement on machined surface quality by means of a series of experiments. Mitutoyo SJ-410 roughness tester is used for collecting surface roughness data in order to analyses the influence of cutting parameters on machined surface roughness.
The values of roughness in five different zones of machined sur-face (rotate along the sursur-face of the cylinder about per 70 degrees) should be measured respectively for the same set of cutting param-eters. The mean value of what left after elimination of maximum and minimum values is taken as the nominal value of surface roughness. The changing trend curve, as shown inFig. 3, of rough-ness corresponding to the variation of cutting parameters can be obtained by means of software Matlab according to the process of surface roughness nominal values. The influence cutting speed, feeding rate or cutting depth on machined surface roughness is shown inFig. 3(a–c) respectively. Three specimens have been used in machining experiments. Red, blue and brown curves inFig. 3
show the relationship between machined surface roughness and cutting parameters corresponding to specimen 1, 2, 3 respectively. It can be seen from Fig. 3(a) that the surface roughness Ra
decreases with the increasing of cutting speed. When the cutting speed is very low, cutting force is pretty large, the cutting chip flows very slow, cutting temperatures goes up to soften the machined composite material or even to result in built-up-edge, so that machined surface quality becomes poor. With the increasing of cut-ting speed, cutcut-ting force and cutcut-ting heat will decrease, and heat
Radial element
Axial element
Cylindrical element
a
b
Fig. 1. (a) Network reinforcement (1 mm dia.). (b) A03190/304 composite specimen.
Table 1
Mechanical properties of the matrix and reinforcement. Material Strength of extension (MPa) Hardness (HB) Yield strength (MPa) Elongation (%) 304 520 187 310 40 A03190 275 100 100 2.5
Fig. 2. The experimental photograph.
Table 2
Cutting parameters.
Item Parameter’s value
Cutting speed vc(m/min) (ap= 0.1 mm, f =0.05 mm/rev) 12.43 17.93 26.24 38.43 57.08 82.43 105.28 151.66 217.60
Feeding rate f (mm/rev) (ap= 0.1 mm, vc= 105.28 m/min) 0.03 0.05 0.06 0.10 0.13 0.15 0.18 0.21 0.30
radiation condition will become better because of cutting chip flow-ing fast, so cuttflow-ing temperature will reduce. In the case of high cut-ting speed, not only tool abrasion is slight, but also no built-up-edge appears. It follows from what mentioned above that the higher the cutting speed, the lower the machined surface roughness value is.
As shown inFig. 3(b), the surface roughness Raincreases in wide
range from less than 4
l
m to more than 20l
m with the increasing of feeding rate from 0.03 mm/rev to 0.30 mm/rev. The section area of left material, that should be cut off from specimen but not removed in fact, will increase with the enlarging of feeding rate. On the other hand, cutting force and cutting temperature will increase, and tool abrasion will become worse as feeding rate increasing, so machined surface quality is going to be worse. According to what analyzed above, the larger the feeding rate, the greater the machined surface roughness value is.It can be seen inFig. 3(c) that machined surface roughness Rais
within a narrow range between 3.3
l
m and 5.1l
m as cutting depth increases from 0.10 mm to 0.90 mm. Surface roughness Radecreases firstly, and then gradually increases with increasing of cutting depth. When cutting depth is very small, some to be removed material is not cut off indeed; extrusion exists beneath cutting edge in fact. So, heavy pressure and abrasion around cut-ting edge makes roughness large. With the increasing of cutcut-ting depth, phenomenon mentioned above is gradually improved, and machined surface roughness value will become smaller. However, if cutting depth increases further as larger than 0.40 mm, machined surface roughness value will increase rather than decrease because the increasing of cutting force results in mean pressure around tool edge going up enough to make abrasion worse.
3.3. Integrity of machined surface on A03190/304 composites Turning results of roughness can illustrate machined surface quality in some extent. However, in the cutting process of A03190/304 composites, there exist several typical defects, such as the attachment or insert of chip and its scratching, the crack on the interface between reinforced phase and matrix phase, the stripping twist of reinforced phase, concave-convex of reinforced phase, tearing of matrix or the surface micro cracks of matrix, which can’t be reflected by machined surface roughness. And they are very important in evaluating the quality of machined surface. 3.3.1. The attachment or insert of chip and its scratching
As research result of reference[3]the phenomena of attach-ment or insert of chip and its scratching are shown in Fig. 4.
Fig. 4(a) shows the attachment of matrix phase chip. Fig. 4(b) shows the insert of reinforcement phase chip and its scratching. The attachment of matrix phase chip is likely to appear at low cut-ting speed or small cutcut-ting depth because chips are excessive cur-ling and get hot bonded on the machined surface. This phenomenon can be avoided by appropriately increasing cutting speed or increasing cutting depth to get cutting process more suit-ably. In the cutting process, reinforcement phase chips flow along rake around the tip of tool nose and appear discontinuously. The hardness of reinforcement phase chip is much higher than that of matrix phase so that scratching will occur when reinforcement phase chip breaks down and forms insert. In comparison with the attachment of matrix phase chip, the impact of machined sur-face quality by insert of reinforcement phase chip is much more seriously.
Fig. 3. The influence of (a) cutting speed on surface roughness, (b) feeding rate on surface roughness and (c) cutting depth on surface roughness.
Matrixphase chip
Reinforcement phase chip
Scratching
a
b
3.3.2. The crack between matrix and reinforcement
If cutting force is large enough during turning process to make the bond between matrix and reinforcement broken down, crack will occur as shown inFig. 5. In other words, too weak cohesive force resulting from poor metallurgical bonding or too large cut-ting force because of heavy cutcut-ting depth and feeding rate will cause cracking. The crack between interfaces can be avoided by improving metallurgical quality or decreasing cutting force by means of reducing cutting depth, reducing feeding rate or increas-ing cuttincreas-ing speed. The crack between interfaces makes the quality of machined surface become worse clearly.
3.3.3. The stripping of reinforcement
If the bonding force between matrix and reinforcement is not strong enough to withstand cutting force, reinforcement will be separated from matrix, so that stripping can be formed as shown inFig. 6. This phenomenon occurs in two cases. One is that cohe-sive force is too weak resulting from poor metallurgical bonding,
the other is cutting force is too large resulting from heavy cutting depth and feeding rate. Stripping makes the quality of machined surface become worse.
3.3.4. The bump of reinforcement
The bump of reinforcement occurs sometimes as crack exists at the boundary of matrix and reinforcement. As shown in Fig. 7, bump of reinforcement is concave or convex close to interface zone between matrix and reinforcement. The height of bump is less than 50
l
m generally.3.3.5. The tearing of matrix and micro cracks of matrix
The tearing of matrix is a large area of surface of matrix material with cracks. As shown inFig. 8(a), the tearing of matrix occurs for A03190/304 composite when cutting speed is 57.08 m/min, feed-ing rate is 0.10 mm/rev and cuttfeed-ing depth is 0.40 mm. The tearfeed-ing of matrix is not happened often. The phenomenon of matrix tear-ing occurs only as cutttear-ing speed is relatively low. As cutttear-ing speed
Matrix
a
b
Reinforcement Matrix f vc f vc Reinforcement Stripping of reinforcement Stripping of reinforcementFig. 6. (a) The stripping as reinforcement axis parallel with cutting speed. (b) The stripping as reinforcement axis perpendicular to cutting speed.
Convex
Concave
a
b
Matrix
Reinforcement
Matrix
Reinforcement
f
v
cf
v
cFig. 7. (a) Concave bump of reinforcement. (b) Convex bump of reinforcement.
Reinforcement
a
b
Reinforcement Matrix Crack f vc Matrix Crackincreases to certain critical value or upper, matrix tearing no longer exists. The micro cracks of matrix are a number of fine short cracks in the direction perpendicular to cutting speed. As shown inFig. 8
(b), the micro cracks of matrix occurs for A03190/304 composite when cutting speed is 105.28 m/min, feeding rate is 0.10 mm/rev and cutting depth is 0.40 mm. The tearing of matrix or micro cracks of matrix can be avoided by means of reducing the feeding rate, cutting depth or increasing cutting speed. The experimental results show that tearing of matrix or micro cracks of matrix will no longer exist when feeding rate is less than 0.06 mm/rev, cutting depth is less than 0.2 mm and cutting speed is greater than 150 m/min.
4. Conclusions
A03190/304 composite specimen, composed of Aluminum alloy A03190 as matrix and nickel–chromium stainless steel 304 as rein-forcement with network wire structure, has been prepared by means of natural casting with metal die. Turning experiments and analysis of roughness and integrity of machined surface on A03190/304 composite with network reinforcement have been done with single-factor experimental method. Experimental results show that: (1) machined surface roughness decreases with the increasing of cutting speed; (2) With the increasing of feeding rate from 0.03 mm/rev to 0.30 mm/rev, machined surface rough-ness increases in wide range from less than 4
l
m to more than 20l
m; (3) Machined surface roughness changes slightly from 3.3l
m to 5.1l
m as cutting depth increases from 0.10 mm to 0.90 mm. The investigation of integrity shows machined surface defects happened such as the attachment or insert of chip and its scratching, crack between matrix and reinforcement, stripping of reinforcement, bump of reinforcement, tearing of matrix and micro cracks of matrix. Experiment results show that machined surface defects can be controlled by means of decreasing feeding rate and cutting depth or increasing cutting speed. The tearing of matrix or micro cracks of matrix will no longer exist when feeding rate is less than 0.06 mm/rev, cutting depth is less than 0.2 mm and cutting speed is greater than 150 m/min.Acknowledgments
This work was supported by Taishan Scholar Engineering Spe-cial Funding, the National Natural Science Foundation of China
(No. 51405195) and Shandong Natural Science Foundation of China (No. ZR2012EEL14).
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