CLADDING TECHNOLOGY SHANXI CO., LTDStudy Note on TiC-VC Wear-Resistant Overlay Electrodes Without Preheating
Literature Overview
This publication by Wang Xinhong, Zou Zengda, Song Sili, and Qu Shiyao from Shandong University, published in the Journal of Welding in 2002 under the Shandong Provincial Natural Science Foundation grant (Z2000F02), addresses a significant practical challenge in hardfacing welding: the development of TiC-VC composite carbide-containing overlay electrodes that do not require preheating of the base metal. The research was conducted jointly between the School of Materials Science and Engineering at Shandong University and the Industry Office of the same institution, reflecting a strong industry-academia collaboration model. The work targets carbon and low-alloy steel substrates commonly encountered in mining, construction machinery, and material handling equipment where abrasive wear dominates failure mechanisms.
Core Technical Content and Microstructure Analysis
The fundamental metallurgical challenge in TiC-VC composite carbide overlay systems lies in balancing three competing requirements: sufficient carbide volume fraction for hardness, adequate matrix toughness to resist spalling, and minimal cracking susceptibility during deposition. The authors demonstrate that the synergistic combination of titanium carbide and vanadium carbide particles, with their respective hardness values of approximately 2500 HV and 1800 HV, creates a composite reinforcement effect that surpasses either carbide type used alone.
The microstructure of the overlay layer consists of a martensitic or austenitic matrix depending on the specific electrode composition, with TiC and VC particles distributed throughout. The key innovation in this work is the electrode design that allows cold welding without preheating. This is achieved through several mechanisms:
- The addition of alloying elements that promote autogenous heat retention during multi-pass welding
- Optimized flux composition that maintains arc stability and provides adequate slag protection even on cold substrates
- Controlled carbon activity in the weld pool that reduces the driving force for carbon segregation and subsequent cracking
- Electrode coating formulation that ensures consistent arc characteristics across a wide range of welding positions
Engineering Practice and Process Parameters
The practical significance of this research cannot be overstated for field maintenance and repair welding operations. In industrial settings, preheating large components is often impractical due to equipment limitations, time constraints, or the inability to apply controlled heat input to massive structures. The following table summarizes typical process parameters for the electrodes developed in this study:
| Parameter | Typical Range | Notes |
|---|---|---|
| Electrode diameter | 3.2 mm to 4.0 mm | Depends on application |
| Welding current (DC) | 80 to 160 A | Inversely proportional to diameter |
| Arc voltage | 22 to 28 V | Maintained constant |
| Travel speed | 200 to 350 mm/min | Affects dilution |
| Preheat temperature | 0 to 100 degrees C | Ambient to mild |
| Interpass temperature | Below 150 degrees C | Critical control parameter |
| Overlay hardness | 55 to 62 HRC | As-welded condition |
| Dilution rate | 10 to 25 percent | Substrate-dependent |
Defect Analysis and Countermeasures
The primary defect risks in cold welding of high-carbon overlay systems include:
- Hydrogen-induced cracking: Mitigated through low-hydrogen electrode coatings and controlled interpass temperatures
- Hot cracking: Addressed by limiting sulfur and phosphorus content and maintaining adequate nickel addition for solidification control
- Cold cracking: Reduced through the autogenous softening effect of multi-pass welding and controlled carbon activity
- Poor bond strength: Managed through proper surface preparation and adequate first-pass penetration
The authors report that the as-welded overlay layer achieves a Rockwell hardness of 55 to 62 HRC with a carbide volume fraction of approximately 35 to 45 percent. The wear resistance, measured by pin-on-disk testing, shows a 3 to 5 times improvement over conventional high-carbon overlay electrodes without requiring any preheating.
Study Insights and Reflections
Reflecting on this work from a contemporary perspective, several observations emerge. First, the research validates the principle that electrode formulation can compensate for unfavorable thermal conditions, which is directly applicable to modern hot-wire TIG and cold metal transfer (CMT) processes where thermal input is deliberately minimized. Second, the composite carbide approach pioneered here has been carried forward into laser cladding and PTA processes where TiC-VC powder mixtures are now standard for severe abrasion applications. Third, the lack of preheating requirement opens the door to robotic application, as automated systems can maintain consistent parameters without the variability introduced by manual preheating procedures.
The work also highlights an important engineering philosophy: rather than always adapting the process to the material, one can adapt the consumable to the process constraints. This mindset has proven invaluable in the development of modern low-dilution overlay technologies. For practitioners working with bimetal products and clad pressure vessels, the principles established here regarding carbide distribution, matrix toughness, and crack resistance remain directly transferable to contemporary overlay design, whether using SMAW, SAW, PTA, or laser methods.