Depositing Ni-WC Wear Resistant Overlays with Hot-Wire Assist Technology

• Author / Creator

  Guest, Stuart Dan

• Seven Ni-WC tubular wires utilized in this study were characterized by the nickel sheath area, powder composition, and overall initial carbide volume fraction of the wire prior to welding. The electrical resistivity of steel, stainless steel, and Ni-WC welding consumables were measured from 25-1200 oC. The electrical resistivity of steel and stainless steel welding consumables are greater than those reported in literature. Tubular Ni-WC resistivity is in good agreement with pure nickel values reported in literature.
  A hot-wire electrode extension model was proposed to predict the current necessary to achieve the semi-solid temperature of the welding consumable at the weld pool free surface. The influence of a GTAW and GMAW leading heat source was quantified and found to play a significant role on the hot-wire melting.
  The hot-wire GTAW process showed significant challenges due to excessive electrode contamination and it might not be viable for typical oil sands or downhole drilling equipment wear protection. GMAW using tubular Ni-WC wires was investigated as a more practical alternative and a range of welding parameters and shielding gases were explored. A previously undocumented phenomenon of the non-wetting behaviour of tungsten carbide on the molten weld pool free surface was observed with high speed videography. Carbide dissolution and non-wetting resulted in GMAW carbide transfer efficiencies of 20-70% within the range of parameters studied.
  Hot-wire GMAW was deemed a viable alternative, with a deposition rate of 5.4 kghr-1, 33% carbide volume fraction, and ASTM G65 Dry Sand/Rubber Wheel Procedure A mass loss of 0.086 grams. Metallographic analysis did not show indications of carbide dissolution using the hot-wire assist technology with a GMAW leading heat source.

• Subjects / Keywords

  • GTAW
  • Tungsten Carbide
  • Hot-Wire
  • GMAW
  • Welding
  • Oil Sands
  • Wear
  • Overlay
  • Ni-WC

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3496G

• 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.