Effect of Welding Current on Ni60 Cr3C2 Plasma Cladding Layer Microstructure and Performance

Literature Overview

This study published in Materials for Mechanical Engineering (2025, Vol. 49, Issue 3, pp. 74-80) by Zhang Yu, Tang Biao, Ma Teng, Bi Lige, and Zhou Heng from Jiamusi University and University of Science and Technology Beijing investigates the effect of plasma welding current on the microstructure and performance of Ni60/Cr3C2 composite cladding layers deposited on Q235 low-carbon steel. The cladding powder consists of Ni60 alloy powder blended with 20% by mass Cr3C2 ceramic powder. The study systematically evaluates five current levels (110, 120, 130, and 140 A) and their influence on the macroscopic morphology, microstructure, hardness, and wear performance of the single-pass cladding layers. The research was supported by the Heilongjiang Provincial Department of Education Basic Research Business Fee Project (2023-KYYWF-0561).

Core Technical Findings

Effect of Welding Current on Macroscopic Morphology

The welding current has a direct and significant influence on the macroscopic appearance of the cladding layer. At 130 A, the cladding surface becomes smooth and flat with good formation quality. However, at 140 A, excessive current causes surface oxidation and burn-off, resulting in degraded formation quality. This establishes an upper limit for the process current at approximately 130 A for this specific powder composition and substrate combination.

Welding Current	Surface Morphology	Melt Height	Melt Depth	Melt Width	Dilution Rate
110 A	Acceptable	Lowest	Shallowest	Narrowest	Lowest
120 A	Good	Moderate	Moderate	Moderate	Moderate
130 A	Smooth and flat	Higher	Deeper	Wider	Higher
140 A	Oxidation and burn-off	Highest	Deepest	Widest	Highest

Phase Composition Evolution

The phase composition of the cladding layer changes significantly with welding current:

At 110 A: γ-Ni(Fe), Cr7C3, and CrB phases are present.
At 130 A and 140 A: γ-Ni(Fe), Cr7C3, CrB, Cr23C6, and Cr3C2 phases are present.

The increase in chromium compound types at higher currents is attributed to the greater melt pool size and deeper penetration, which increases the dilution rate and introduces more Fe and C from the Q235 base metal into the cladding layer. The additional carbon and iron promote the formation of Cr23C6 and retain more Cr3C2 in the microstructure.

Hardness and Wear Performance

The hardness and wear performance exhibit a non-monotonic relationship with welding current, following a trend of initial increase followed by decrease:

Welding Current	Hardness Trend	Carbide Quantity	Wear Performance
110 A	Lower	Fewer	Higher wear loss
120 A	Increasing	Increasing	Improving
130 A	Maximum	Maximum, flower-shaped morphology	Best (lowest wear mass loss)
140 A	Decreasing	Decreasing	Worse (higher wear loss)

At 130 A, the cladding layer exhibits the finest microstructure, the highest number of carbides, and a distinctive flower-shaped morphology with Cr-based carbides at the center. This microstructural configuration provides the optimal combination of hardness, carbide dispersion, and matrix support for wear resistance.

Process Analysis and Metallurgical Interpretation

Non-Monotonic Property Response

The non-monotonic relationship between welding current and cladding performance is a critical finding that has important implications for process optimization. The initial improvement from 110 A to 130 A is attributed to:

Increased melt pool energy promoting more complete powder melting and better metallurgical bonding.
Enhanced convective mixing reducing compositional segregation.
Increased dilution rate introducing additional carbon from the base metal, which promotes carbide formation.

The subsequent degradation from 130 A to 140 A is attributed to:

Excessive melt pool size causing surface oxidation and burn-off.
Over-dilution reducing the Ni and Cr content in the cladding layer.
Coarsening of the microstructure due to excessive thermal input.
Reduced carbide number density due to coalescence and dissolution.

Flower-Shaped Microstructure at 130 A

The distinctive flower-shaped morphology observed at 130 A, with Cr-based carbides at the center, is a result of the specific solidification conditions at this current level. The moderate thermal input and dilution rate create conditions that favor the nucleation and growth of Cr carbides in a radial pattern from a central nucleation site. This morphology is beneficial for wear resistance because the radial arrangement of hard carbides provides multiple contact points for load-bearing during sliding wear, distributing the contact stress more uniformly.

Engineering Practice Implications

Application to Abrasive Wear Protection

Ni60/Cr3C2 composite cladding is widely used for protecting components against abrasive and erosive wear in mining, cement, and oil and gas industries. The Q235 base steel is a common substrate for structural components, and the good metallurgical bonding achieved in this study confirms the feasibility of applying this cladding system to low-carbon steel components.

Process Control Recommendations

The optimal welding current of 130 A should be maintained within a tight tolerance (±5 A) to ensure consistent cladding quality.
Visual inspection of the cladding surface should be performed after each pass to detect any signs of oxidation