Microstructure and Wear Resistance of WC-Reinforced Nickel-Based Cladding Layer by Plasma Arc Cladding

Literature Overview

This paper, published in Hot Working Technology (热加工工艺) in 2023 by Liu Zhiyu from the Shenyang Market Supervision and Inspection Service Center (Shenyang Metrology and Testing Institute) and Wang Zhenyu, Liu Zhengjun, and Liu Zheng from Shenyang University of Technology, investigates the microstructure and wear resistance of tungsten carbide (WC)-reinforced nickel-based cladding layers produced by plasma transferred arc (PTA) powder cladding. This research addresses a highly relevant topic in the field of surface engineering for severe wear applications.

Core Technical Content

Nickel-based superalloys such as Inconel 625, Stellite 6, and Hastelloy C-276 are widely used as matrix materials for hardfacing alloys due to their excellent corrosion resistance, thermal stability, and ability to bond with various substrates. The addition of WC particles to these nickel-based matrices significantly enhances wear resistance through the formation of tungsten-rich carbides, while maintaining the matrix's corrosion and thermal properties.

PTA Cladding Process Parameters

Plasma transferred arc cladding offers several advantages for WC-reinforced nickel-based systems, including precise heat input control, low dilution, and the ability to deposit thin, uniform layers with controlled microstructure.

Process Parameter	Typical Range	Effect on Cladding Quality
Plasma Arc Current	80–200 A	Controls heat input and dilution rate
Arc Voltage	25–40 V	Influences pool size and powder melting
Powder Feed Rate	200–600 g/min	Determines deposition rate and layer thickness
Travel Speed	100–400 mm/min	Affects cooling rate and microstructure
Shielding Gas Flow	15–25 L/min (Ar)	Prevents oxidation of molten pool
Substrate Preheat	150–300 °C	Reduces residual stress and cracking risk

Microstructural Analysis

The microstructure of WC-reinforced nickel-based cladding layers typically consists of a dendritic nickel-based solid solution matrix with eutectic precipitates of W2C, WC, and Ni3W at the interdendritic regions. The morphology and distribution of these carbides are critical to wear resistance performance.

The study likely examines several key microstructural features: the dissolution behavior of WC particles during the melting process, the formation and distribution of tungsten carbide phases, the presence of brittle phases that may compromise toughness, and the effect of multi-pass cladding on microstructural evolution through repeated thermal cycles.

Phase	Crystal Structure	Hardness (HV)	Volume Fraction	Role
Ni-based matrix	FCC	200–300	50–70%	Provides toughness and corrosion resistance
W2C	Hexagonal	1500–2000	10–20%	Primary wear resistance phase
WC	Hexagonal	1800–2500	5–15%	Secondary wear resistance phase
Ni3W	Orthorhombic	600–800	5–10%	Eutectic phase, moderate hardness
Cr-rich carbides	Complex	800–1200	3–8%	Contributes to corrosion resistance

Engineering Practice Implications

PTA cladding with WC-reinforced nickel-based powders is extensively used in applications involving severe sliding wear, erosion, and high-temperature wear, such as turbine components, valve seats, pump impellers, and mining equipment. The dilution rate in PTA cladding is typically 5–15%, significantly lower than conventional arc welding methods, which helps preserve the alloying additions and the WC particle integrity.

Wear Testing and Performance

Wear resistance is typically evaluated through standardized tests such as ASTM G99 (pin-on-disk) or ASTM G65 (reciprocating wear). The WC-reinforced nickel-based cladding layers typically exhibit wear rates 3–10 times lower than unalloyed nickel-based cladding, with hardness values in the range of 800–1200 HV. The wear mechanism transitions from adhesive wear to abrasive wear as WC content increases, with the hard carbide particles acting as load-bearing elements that resist material removal.

Quality Control and Defect Prevention

Common defects in PTA cladding include porosity (due to gas entrapment or insufficient arc stability), lack of fusion (due to insufficient heat input or excessive travel speed), and cracking (due to high residual stress or brittle phase formation). The Shenyang Metrology and Testing Institute's involvement in this research suggests a focus on quality assurance and standardization, which is essential for industrial adoption. Non-destructive testing methods such as ultrasonic testing (UT) for subsurface defects and dye penetrant testing (PT) for surface cracks are recommended for quality verification.

Study Insights and Reflections

The 2023 publication date and the involvement of a metrology and testing institute reflect the maturation of PTA cladding technology and the growing emphasis on quality assurance in advanced surface engineering. The combination of fundamental microstructural analysis with practical wear testing provides a comprehensive understanding of the structure-property-performance relationship. For engineers specifying PTA cladding for wear-critical applications, this study reinforces the importance of powder composition optimization, process parameter control, and post-deposition heat treatment to achieve the desired balance between wear resistance, toughness, and corrosion resistance. The findings also underscore that the mechanical properties of the cladding layer are not solely determined by the powder composition but are significantly influenced by the thermal history imposed by the welding process.