Tribological properties of composite materials obtained using electrodepositing

TRIBOLOGICAL PROPERTIES OF COMPOSITE MATERIALS OBTAINED USING ELECTRODEPOSITING

ABSTRACT

The resistance to abrasive wear of composite materials obtained using electrodepositing in nickel and copper matrix was studied. The samples containing composite layers of graphite in copper matrix, titan dioxide and zirconium dioxide in nickel matrix were subjected to the wear process using a pin-disc type testing machine.

KEYWORDS composite coating, tribological properties.

1.Introduction

The tribology concept refers to the interaction between two or more bodies with one or more surfaces in contact, with or without macroscopic relative motion, in order to transmit normal or tangential forces. The process of friction-wear is a complex one, producing modifications in the geometry and structure of the superficial layers that are in contact with each other; this phenomenon leads to losses of material reducing the precision and the efficiency of machines and tools. In the automotive industry there are many parts affected by the wear which lead to the replacing of the traditional materials with composite materials:

Table1 The use of composite materials in the automotive industry [1]

Good tribological properties are also seen in the case composite coverings with metallic matrix obtained using electrodepositing; in the case of these composite materials the properties of the metallic matrix are improved by adding the disperse phase that is in the form of powder.

2.The experimental method

We studied the tribological behavior of many samples made using electrodepositing. We deposited TiO₂ and ZrO ₂ in nickel matrix and graphite in copper matrix; we obtained composite materials with one or two layers deposited. All the electrodeposits were made on a copper basis. The technological scheme was the following one: Electrodepositing , Drying, Punching , Degreasing , Abrasive wear resistance testing.

Table2 Characterization of samples depending on the nature of matrix and dispersed phase

2.1 Abrasive wear resistance testing

The machine used in order to check the abrasive wear resistance is a pin-disc type one. The sample is introduced in a puncher that presses with a certain force upon a rotating disc covered with abrasive paper. The sample executes a spiraling motion on the disc with the help of a mechanism. All the samples were pressed against the disc with the same force and have travelled the same distance. At the end of the testing the mass loss of each sample was measured. The variation of the mass was established by weighing with a scale with the precision of 1x10^-3 grams.

Fig.1 The scheme of the abrasive wear resistance testing machine

1-    puncher , 2- sample , 3- abrasive paper , 4- metallic disc , 5- pressing force , 6- the rotation movement of the disc , 7-the movement of the sample on the disc

3. Results and discussions

For the wear testing we used samples with a disc shape with a diameter of 10 mm. The pressing force was made using the weight of the puncher, respectively 126 grams. The length of the distance travelled by each sample was 7.5 m. We used samples obtained by the electrodepositing on a copper basis. We have measured the mass of the sample before and after the wear testing. The results were the following:

Table 3 The variation in mass of the samples before and after the wear testing.

Fig.2 The microstructure of the sample T67 (x500)

(the basis is made of copper, matrix of nickel and TiO₂ is the dispersed phase)

Fig.3 The microstructure of the sample Z45(x 1000)

the basis is made of copper, matrix of nickel and ZrO₂ is the dispersed phase)

Fig.4 The microstructure of the sample G 40(x 1000)

the basis is made of copper, matrix of coper and graphite is the dispersed phase)

Fig.5 SEM micrograph of dual-layer composite film( first layer is made of copper , the matrix of the second layer is made of nickel and TiO₂ is the dispersed phase).

Fig.6 The variation of the mass of the samples according to the depositing type.

4. Conclusions

The samples obtained using the electrodepositing of 2 layers (Ni+ TiO₂/Ni+ ZrO₂) respectively M₁₁ and M₁₂ have shown the best resistance to wear. Out the samples with a single layer the best wear resistance was noticed in the case of Z₂₁ and Z₄₅ (Ni+ZrO₂); more intense wear was noticed in the case of the samples T₆₇ and T₃₅ (Ni+TiO₂) and the maximum wear was in the case of the samples G₄₀ and G₂₅ (Cu+ graphite). Different wear behavior can be explained by the fact that deposited layers have different microhardness; matrices are also different( nickel with higher wear resistance than copper).

References

[1] PhD. Eng. CIUNEL Stefanita , Prof. Dr. Eng. MANGRA Mihail, Actual tendencies in the usage of composite materials in the automotive industry, 8^th INTERNATIONAL CONFERENCE Targu-Jiu, May 24-26 , 2002, "CONSTANTIN BRANCUSI" UNIVERSITY ,ENGINEERING FACULTY.

[2] O.Mitoseriu,E.Drugescu,F.Potecasu,L.Benea,G.Carac ,1998,Composite Coatings Obtained by Sedimentation Codeposition During Copper, Cobalt and Iron Electroplating, - International Journal MATERIALS AND MANUFACTURING PROCESSES (USA), VOL XI, ISSN1042-6914, pages 417-422.

[3] S.R. Saifulin, 1992, Physical Chemistry of Inorganic Polymeric and Composite Materials, Ellis Horwood Ltd. London, New York

[4]. J.P. Celis , Developments and future challenges to science and technology in the field of tribocorrosion , Proc. Eurocorr 2005, The European Corrosion Congress , 4-8 September 2005 , Lisbon, Portugal.

[5] A. de Vooys, J.P. Celis , Tribological and electrical performance of composite nickel and copper coatings as connector material on steel strips , Appliance Manufacturing (2004) , S. 48 .