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Journal of Materials Processing Technology 155156 (2004) 19231926

Comparative wear characteristics of tin and ticcoated and uncoated tool steel

A.E. Zeghni, M.S.J. HashmiNCPST-MPRC, Dublin City University, Dublin, Ireland

Abstract

Wear characteristics of TiN and TiC coatings deposited by magnetron sputtering on D2 and D3 tool steels in contact dry sliding

conditions have been investigated and compared to the uncoated. The thin films (4m) were characterised in their adhesion, hardness

and chemically analysed. The results showed that TiC coated samples demonstrate greater wear resistance, with TiC D2 steel showed thebest wear resistance. It was found that the substrate materials have an influence on the hardness and wear resistance of the system.

2004 Elsevier B.V. All rights reserved.

Keywords:TiN; TiC; Tool steels; Wear

1. Introduction

Application of thin films having high resistance to wear

due to their hardness and high mechanical strength have

been increasing in various industrial fields [1]. These areas

of application of coatings and surface treatment in general

are where the combination of the properties, both the sub-strate and treatment is required. Among many hard coatings

TiN and TiC are the most widely used ceramics coatings in

the cutting tools due to their high hardness and wear resis-

tance, low coefficient of friction, high temperature strength

and chemical stability[24].Application of TiN and TiC by

PVD or CVD to tool steel reduced the wear up to six times,

wear testing of D3 steel showed that the wear of TiN coated

D3 was between 4 and 24% of the uncoated samples de-

pending on the surface roughness of the initial surface [5,6].

Sundquist et al.[6]proposed that increase in the wear resis-

tance of tool life coated with TiN can be expected only when

the roughness of the surface is less than the coating thick-

ness. It is well known that the performance of the coating

under wear conditions very far depending on the hardness

and the quality of the coating deposited to the substrate. In

the present study, a comparison made between wear resis-

tance of TiC and TiN coatings applied on D2 andD3 tool

steels using magnetron sputtering technique. Hardness and

adhesion of coated samples, were measured and their influ-

ence on wear resistance of the system investigated.

Corresponding author.

E-mail addresses:adel.zeghni2@mail.dcu.ie (A.E. Zeghni),

saleem.hashmi@dcu.ie (M.S.J. Hashmi).

2. Experimental

2.1. Test apparatus and procedure

Fig. 1 shows a schematic diagram of the wear test rig,

which was developed to carry out impact and abrasion wear

tests. It consists of substrate table with two clamps to holdthe sample in apposition against a tungsten carbide wear

tool (stylus) which fixed in a tool holder by grove screw. A

contacted arm is attached in one of its sides to the motor

shaft (.75 kW, Hanning Elektro werkes) and from the other

side hinged to the to the plate form which provides the slid-

ing mechanism of the wear tool. As the motor shaft rotates,

crank and connecting arm translates rotary motion into recip-

rocated motion and the plate form starts sliding. As the tool

holder placed through the square hole in the platform, the

stylus comes in contact with the sample surface to produce

wear once the stylus slides. A revolution counter records the

number of revolution of the motor out put shaft. The sample

was clamed on the substrate table, the connecting arm ad-

justed for the desired sliding distance (20 mm). After setting

the wear tool on the sample surface, the desired wear load

(5 kg) applied. As the motor is switched on, the tool starts

sliding and the revolution counter records the number of cy-

cles which the sample subjected to in order to produce wear.

After low number of cycles, the sample declamped and taken

for wear measurement, then the process repeated until de-

sired wear depth was attained. The wear loss of the coatings

was too small to be resolved by weighing. Instead a stylus

profilometer was used to measure the wear track depth. A

Mitutoyo Surftest 402, Series 178 instrument, with added

0924-0136/$ see front matter 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.jmatprotec.2004.04.282

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1924 A.E. Zeghni, M.S.J. Hashmi / Journal of Materials Processing Technology 155156 (2004) 19231926

Fig. 1. Schematic diagram of the wear rig.

feature of chart recorder was used to measure the wear trackdepth. This provides profile and roughness of the surface.

2.2. Test material

2.2.1. Substrate material

Two different, widely used in industry tool steels were

used as substrate material. D2 and D3 high carbon high

chromium cold-work steels were cut and prepared for coat-

ing.Table 1shows the chemical composition and the hard-

ness of the two materials.

2.2.2. Coating Materials

TiC and TiN were commercially deposited using mag-

netron sputtering with a thickness (4m) the typical pro-

cess for these films including:

(i) wet cleaning;

(ii) heating;

(iii) etching;

(iv) coating and

(v) cooling.

2.3. Film Characterisation

2.3.1. AdhesionA Rockwell indenter (Indetec 8150bK) used to measure

the quality of the adhesion of the films by indentation

method.

Table 1

Chemical composition of the tool steels

Material Contents (%) Hardness

(Rc)C Si Mn Cr Co W V

AISI D2 1.55 0.3 0.3 12 0.8 0.8 63

AISI D3 2.05 0.3 0.8 12 1.3 60

2.3.2. HardnessThe micro hardness measurements were performed, using

a Leitz Mini load Vickers hardness, indentations were made

with 0.2 N load.

2.3.3. Chemical characterisation

The films were chemically characterised using X-Ray en-

ergy dispersive analysis (EDX). Where, the electron beam

from the SEM serves to excite characteristic X-rays from

the area of the specimen being probed[7]. The objective of

the chemical characterisation was to measure the element

composition of the coatings.

3. Results and discussion

3.1. Wear test results

Coating is applied to the surfaces to increase its wear re-

sistance. This can be indicated by less material loss of the

coated material over the uncoated one. Wear track depth as

function of number of cycles of coated and uncoated D2 and

D3 steels are shown inFigs. 2 and 3.It was shown that the

TiN coated surface demonstrated in general lower wear than

uncoated surfaces. However, TiC coated surfaces demon-

strated much lower wear than the uncoated surfaces. These

figures also sowed that TiN and TiC surfaces worn out slower

than the uncoated surfaces and TiC surfaces is the slower of

all. It was observed that when the coating broken the wear

rate increased and then it started again to be at the same

level as of the uncoated surfaces. This may be explained as

the coating broken the hard fragments acted as third body

and increased the loss of material and when the coating was

totally removed, wear became only of the substrate material.

This leads to the suggestion that hard coatings may cause

sever wear when they broken. The influence of the substrate

material can be shown in Fig. 4. Combination of D2 steel

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A.E. Zeghni, M.S.J. Hashmi / Journal of Materials Processing Technology 155156 (2004) 19231926 1925

Fig. 2. Wear track depth vs. No. of cycles of coated and uncoated D2 tool steels.

Fig. 3. Wear track depth vs. No. of cycles of coated and uncoated D3

tool steel.

with the coatings showed better wear resistance than D3 steel

with the same coatings. This findings supports what some

researchers, such as Bromark et al.[8],concluded about the

effect of the substrate material properties on the over all tri-

bological properties of the coating substrate composite.

3.2. Hardness

Micro hardness value of coated and uncoated samples

are shown in Fig. 5. The composite hardness was found

Fig. 4. Wear track depth vs. No. of cycles of coated D2 and D3 tool steels.

Fig. 5. Micro hardness values of coated and uncoated samples.

to increase in the order TiN/D3 < TiN/D2 < TiC/D3