title: [The effect of solid phase transformation on the metal-ceramic compatibility of Co-Cr alloy].
abstract: OBJECTIVE
  To study the effect of solid phase transformation on the metal-ceramic compatibility of Co-Cr alloy during firing programs.
  
  
  METHODS
  9 foils of Co-Cr and Ni-Cr alloy with the dimension of 25 mmx3 mmx0.5 mm were casted using lost wax technology respectively. Among them, 6 specimens were subjected to metal-ceramic bonding strength test (three point bending method), the ceramic layer of 3 specimens were removed for X-ray diffraction (XRD) analysis. One cylindrical specimen of each alloy was casted for the test of coefficient of thermal expansion, cooling curves were recorded.
  
  
  RESULTS
  The metal-ceramic bonding strength of Ni-Cr, Co-Cr alloy was (49.1 +/- 3.40), (40.9 +/- 2.02) MPa respectively. There was significant difference between the two groups' bonding strength (P = 0.00). The coefficient of thermal expansion in the 20-500 degrees C interval of Ni-Cr and Co-Cr alloy was 13.9 x 10(-6), 13.8 x 10(-6) x K(-1) respectively. XRD analysis indicated that the microstructure of Ni-Cr alloy was austenite. While Co-Cr alloy was constituted by fcc phase, hcp phase and sigma phase.
  
  
  CONCLUSIONS
  During the cooling procedure, the transformation of fcc phase to hcp phase and segregation of needle-like sigma phase intensify the linear contraction speed of Co-Cr alloy, which decreases the metal-ceramic adaptability.
authors.affiliation: School of Manufacturing Science and Engineering, Sichuan University, Chengdu 610059, China.
authors.forename: Zhikai
authors.initials: Z
authors.lastname: Wu
authors.forename: Sheng
authors.initials: S
authors.lastname: Xu
authors.forename: Ning
authors.initials: N
authors.lastname: Li
mesh_terms: D000497:Alloys; D002516:Ceramics; D002858:Chromium Alloys; D003722:Dental Alloys; D001840:Dental Bonding; D003776:Dental Porcelain; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D008670:Metals
chemical_list: D000497:Alloys; D002858:Chromium Alloys; D003722:Dental Alloys; D016876:Metal Ceramic Alloys; D008670:Metals; D003776:Dental Porcelain; C093826:Austenite