Microcracks were mechanically induced in the CVD coating layers on two types of cemented carbides with different thermal expansion coefficients, and one type of cermet. The microcracks were found to have beneficial effects on residual stress, transverse rupture strength, and chipping resistance during interrupted cutting. Residual stress in the coating on cemented carbide is tensile. Tensile residual stress decreases with increasing microcrack width and decreasing microcrack distance. Induction of 20 μm-distant and 0.025 μm-wide cracks relieves tensile residual stress by about 0.5 GPa, increases transverse rupture strength by about 0.70 GPa, and almost doubles the chipping resistance. Residual stress in the coating on cermet is compressive. Microcracks in the coating layer do not change residual stress or transverse rupture strength.

1.
Stjernberg, K. G., 1980, “Fracture Toughness of TiC-Coated Cemented Carbides,” Metal Science, May, pp. 189.
2.
Suzuki
H.
, and
Hayashi
K.
,
1981
, “
The Strength Decrease in WC-Co Cemented Carbides Having Coated-Layer by CVD
,”
Journal of the Japan Society of Powder and Powder Metallurgy
, Vol.
28
, pp.
257
259
.
3.
Yamamoto
T.
, et al.,
1986
, “
An X-ray Study of Residual Stress Generated in Cemented Carbide, Coated with TiN by CVD Process and PVD Process
,”
J. Japan Inst. Metals
, Vol.
50
, pp.
320
327
.
4.
Katayama
S.
, et al.,
1991
, “
Effect of Microcracks in CVD-Coated Layer on Transverse Rupture Strength and Chipping Resistance
,”
Annals of CIRP
, Vol.
40
, No.
1
, pp.
57
60
.
5.
Katayama
S.
, et al.,
1991
, “
Development of CVD Coated Carbide Tool with High Chipping Resistance
,”
J. Japan Inst. Metals
, Vol.
30
, No.
4
, pp.
298
300
.
6.
Yamamoto
T.
, and
Kamachi
K.
,
1985
, “
The Surface Residual Stress of Cemented Carbides Coated with TiC or TiN by Chemical Vapour Deposition Process and Physical Vapour Deposition Process
,”
J. Japan Inst. Metals
, Vol.
49
, pp.
120
124
.
7.
Japanese Standard Association, JAPANESE INDUSTRIAL STANDARD JIS B 4053.
8.
Lawn
R. B.
, and
Evans
A. G.
,
1980
, “
Elastic/Plastic Indentation Damage in Ceramics
,”
Journal of The American Ceramic Society
, Vol.
63
, No.
9–10
, pp.
575
575
.
9.
Suzuki
H.
, et al.,
1985
, “
Residual compressive Stress in Ti(C, N) Layer Deposited on Cemented Carbide by the PVD process
,”
J. Japan Inst. Metals
, Vol.
490
, No.
9
, pp.
773
778
.
10.
Suzuki
H.
, et al.,
1984
, “
Transverse Rupture strength of WC-Co Alloys Coated with Titanium Nitride by PVD Process
,”
Journal of the Japan Society of Powder Metallurgy
, Vol.
31
, No.
3
, pp.
20
25
.
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