Microstructure and properties of Ni-alloy and Ni-WC composite overlays

• Author / Creator

  Liyanage, Thilan

• The microstructures and performance of Ni-based alloys and Ni-WC (nickel-tungsten carbide) composite overlays deposited by plasma transferred arc welding have been studied. The Ni-alloy overlays had similar microstructures consisting of Ni dendrites, with interdendritic Ni-based eutectics, borides and carbides. Low hardness alloy overlays contained a smaller fraction of interdendritic phases relative to the high hardness alloys. The interdendritic regions make a significant contribution to the hardness since they are more than twice as hard as primary dendrites.
  The Ni-WC composites contained similar phases, however WC dissolution was observed leading to the formation of other carbides. Ni-alloys with low carbon and Cr content exhibited the lowest WC dissolution. The Ni-WC overlays produced using these dilute alloys generally performed better in ASTM G65 wear tests. This was likely due to the reduced dissolution which avoided formation of brittle secondary phases, maintaining a short mean free path between WC particles and allowing increased impact energy absorption.

• Subjects / Keywords

  • Dissolution
  • PTA
  • MMC
  • NiBSi
  • WC
  • NiCrBSi
  • Micro-structure

• Graduation date

  Fall 2010

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3HB0Z

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.