Evaluations of fatigue crack growth characteristics of sintered and thermal-sprayed WC-Co materials

Tatsunori Sunoucchi, Hideo Cho, Kenichi Sakaue, Takeshi Ogawa, Yoshifumi Kobayashi

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Fatigue crack growth characteristics were investigated for sintered and thermal-sprayed tungsten carbide with cobalt (WC-Co) cermets. Acoustic emission (AE) techniques were applied to study the crack growth mechanism. The materials used were two types of sintered WC-Co materials, commercially available as G5 and KD20 with the WC grain sizes of 1.0-8.0/μm and 0.5-1.5μm, respectively, and 7mm thick sprayed layer with the WC grain size of 0.5-1.5μm. The Co content (mass %) of these materials were 12-13%. Compact type (CT) specimens were employed for fracture mechanics experiments in accordance with ASTM E647-95a. AE source wave analysis enabled us to estimate the crack volume dynamically developed near the crack tip. The fatigue crack growth rate, da/dN, depended on the WC grain size as well as the stress ratio for the sintered materials, and it was accelerated in sprayed material because of the existence of micro-pores. When these da/dN were compared with structural steels and aluminum alloy as a function of effective stress intensity factor, ΔKeff, normalized by Young's modulus, E, they were much higher than those of the structural materials. This behavior was due to the brittle inter-granular (IG) fracture of WC particle, whose contributions were estimated by AE analysis and fracture surface observations. AE source wave analysis revealed that fracture volume of the IG fracture corresponded to the WC grain size and thus the IG fracture assumed to occur at the individual WC particles. The results of maximum stress intensity factor, Kmax, constant, ΔK decreasing tests suggested that the frequency of the IG fracture of the WC particle was controlled by Kmax. In the threshold region, the contribution of the IG fracture decreased and the threshold value of ΔKeff tended to be constant for sintered materials, while it was lower for sprayed material due to the micro-pores.

Original languageEnglish
Pages (from-to)1037-1043
Number of pages7
JournalZairyo/Journal of the Society of Materials Science, Japan
Volume58
Issue number12
DOIs
Publication statusPublished - 2009 Dec
Externally publishedYes

Fingerprint

Fatigue crack propagation
cracks
acoustic emission
Acoustic emissions
evaluation
grain size
stress intensity factors
Stress intensity factors
stress ratio
porosity
cermets
tungsten carbides
thresholds
fracture mechanics
Tungsten carbide
Cermets
crack tips
Alloy steel
Cobalt
Hot Temperature

Keywords

  • Acoustic emission
  • Fatigue crack growth
  • Fracture mechanism
  • Fracture volume
  • Sintered and sprayed materials
  • WC-Co cermet

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanical Engineering
  • Mechanics of Materials
  • Condensed Matter Physics

Cite this

Evaluations of fatigue crack growth characteristics of sintered and thermal-sprayed WC-Co materials. / Sunoucchi, Tatsunori; Cho, Hideo; Sakaue, Kenichi; Ogawa, Takeshi; Kobayashi, Yoshifumi.

In: Zairyo/Journal of the Society of Materials Science, Japan, Vol. 58, No. 12, 12.2009, p. 1037-1043.

Research output: Contribution to journalArticle

Sunoucchi, Tatsunori ; Cho, Hideo ; Sakaue, Kenichi ; Ogawa, Takeshi ; Kobayashi, Yoshifumi. / Evaluations of fatigue crack growth characteristics of sintered and thermal-sprayed WC-Co materials. In: Zairyo/Journal of the Society of Materials Science, Japan. 2009 ; Vol. 58, No. 12. pp. 1037-1043.
@article{1c01fb1ebd644742bf237f815e5e60b5,
title = "Evaluations of fatigue crack growth characteristics of sintered and thermal-sprayed WC-Co materials",
abstract = "Fatigue crack growth characteristics were investigated for sintered and thermal-sprayed tungsten carbide with cobalt (WC-Co) cermets. Acoustic emission (AE) techniques were applied to study the crack growth mechanism. The materials used were two types of sintered WC-Co materials, commercially available as G5 and KD20 with the WC grain sizes of 1.0-8.0/μm and 0.5-1.5μm, respectively, and 7mm thick sprayed layer with the WC grain size of 0.5-1.5μm. The Co content (mass {\%}) of these materials were 12-13{\%}. Compact type (CT) specimens were employed for fracture mechanics experiments in accordance with ASTM E647-95a. AE source wave analysis enabled us to estimate the crack volume dynamically developed near the crack tip. The fatigue crack growth rate, da/dN, depended on the WC grain size as well as the stress ratio for the sintered materials, and it was accelerated in sprayed material because of the existence of micro-pores. When these da/dN were compared with structural steels and aluminum alloy as a function of effective stress intensity factor, ΔKeff, normalized by Young's modulus, E, they were much higher than those of the structural materials. This behavior was due to the brittle inter-granular (IG) fracture of WC particle, whose contributions were estimated by AE analysis and fracture surface observations. AE source wave analysis revealed that fracture volume of the IG fracture corresponded to the WC grain size and thus the IG fracture assumed to occur at the individual WC particles. The results of maximum stress intensity factor, Kmax, constant, ΔK decreasing tests suggested that the frequency of the IG fracture of the WC particle was controlled by Kmax. In the threshold region, the contribution of the IG fracture decreased and the threshold value of ΔKeff tended to be constant for sintered materials, while it was lower for sprayed material due to the micro-pores.",
keywords = "Acoustic emission, Fatigue crack growth, Fracture mechanism, Fracture volume, Sintered and sprayed materials, WC-Co cermet",
author = "Tatsunori Sunoucchi and Hideo Cho and Kenichi Sakaue and Takeshi Ogawa and Yoshifumi Kobayashi",
year = "2009",
month = "12",
doi = "10.2472/jsms.58.1037",
language = "English",
volume = "58",
pages = "1037--1043",
journal = "Zairyo/Journal of the Society of Materials Science, Japan",
issn = "0514-5163",
publisher = "Society of Materials Science Japan",
number = "12",

}

TY - JOUR

T1 - Evaluations of fatigue crack growth characteristics of sintered and thermal-sprayed WC-Co materials

AU - Sunoucchi, Tatsunori

AU - Cho, Hideo

AU - Sakaue, Kenichi

AU - Ogawa, Takeshi

AU - Kobayashi, Yoshifumi

PY - 2009/12

Y1 - 2009/12

N2 - Fatigue crack growth characteristics were investigated for sintered and thermal-sprayed tungsten carbide with cobalt (WC-Co) cermets. Acoustic emission (AE) techniques were applied to study the crack growth mechanism. The materials used were two types of sintered WC-Co materials, commercially available as G5 and KD20 with the WC grain sizes of 1.0-8.0/μm and 0.5-1.5μm, respectively, and 7mm thick sprayed layer with the WC grain size of 0.5-1.5μm. The Co content (mass %) of these materials were 12-13%. Compact type (CT) specimens were employed for fracture mechanics experiments in accordance with ASTM E647-95a. AE source wave analysis enabled us to estimate the crack volume dynamically developed near the crack tip. The fatigue crack growth rate, da/dN, depended on the WC grain size as well as the stress ratio for the sintered materials, and it was accelerated in sprayed material because of the existence of micro-pores. When these da/dN were compared with structural steels and aluminum alloy as a function of effective stress intensity factor, ΔKeff, normalized by Young's modulus, E, they were much higher than those of the structural materials. This behavior was due to the brittle inter-granular (IG) fracture of WC particle, whose contributions were estimated by AE analysis and fracture surface observations. AE source wave analysis revealed that fracture volume of the IG fracture corresponded to the WC grain size and thus the IG fracture assumed to occur at the individual WC particles. The results of maximum stress intensity factor, Kmax, constant, ΔK decreasing tests suggested that the frequency of the IG fracture of the WC particle was controlled by Kmax. In the threshold region, the contribution of the IG fracture decreased and the threshold value of ΔKeff tended to be constant for sintered materials, while it was lower for sprayed material due to the micro-pores.

AB - Fatigue crack growth characteristics were investigated for sintered and thermal-sprayed tungsten carbide with cobalt (WC-Co) cermets. Acoustic emission (AE) techniques were applied to study the crack growth mechanism. The materials used were two types of sintered WC-Co materials, commercially available as G5 and KD20 with the WC grain sizes of 1.0-8.0/μm and 0.5-1.5μm, respectively, and 7mm thick sprayed layer with the WC grain size of 0.5-1.5μm. The Co content (mass %) of these materials were 12-13%. Compact type (CT) specimens were employed for fracture mechanics experiments in accordance with ASTM E647-95a. AE source wave analysis enabled us to estimate the crack volume dynamically developed near the crack tip. The fatigue crack growth rate, da/dN, depended on the WC grain size as well as the stress ratio for the sintered materials, and it was accelerated in sprayed material because of the existence of micro-pores. When these da/dN were compared with structural steels and aluminum alloy as a function of effective stress intensity factor, ΔKeff, normalized by Young's modulus, E, they were much higher than those of the structural materials. This behavior was due to the brittle inter-granular (IG) fracture of WC particle, whose contributions were estimated by AE analysis and fracture surface observations. AE source wave analysis revealed that fracture volume of the IG fracture corresponded to the WC grain size and thus the IG fracture assumed to occur at the individual WC particles. The results of maximum stress intensity factor, Kmax, constant, ΔK decreasing tests suggested that the frequency of the IG fracture of the WC particle was controlled by Kmax. In the threshold region, the contribution of the IG fracture decreased and the threshold value of ΔKeff tended to be constant for sintered materials, while it was lower for sprayed material due to the micro-pores.

KW - Acoustic emission

KW - Fatigue crack growth

KW - Fracture mechanism

KW - Fracture volume

KW - Sintered and sprayed materials

KW - WC-Co cermet

UR - http://www.scopus.com/inward/record.url?scp=77950995704&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77950995704&partnerID=8YFLogxK

U2 - 10.2472/jsms.58.1037

DO - 10.2472/jsms.58.1037

M3 - Article

VL - 58

SP - 1037

EP - 1043

JO - Zairyo/Journal of the Society of Materials Science, Japan

JF - Zairyo/Journal of the Society of Materials Science, Japan

SN - 0514-5163

IS - 12

ER -