Research Status and Progress of Plasma Arc Powder Cladding Materials

Literature Overview

This 2020 comprehensive review by Wei Shiyong, Peng Wenyi, Chen Bin, Zhao Wenchao, Zhou Yingyu, and Deng Xiaohua from Nanchang University and the Jiangxi Academy of Applied Physics provides a systematic overview of plasma transferred arc (PTA) powder cladding materials. Published in Materials Reports, this work was supported by the National Natural Science Foundation of China and the Jiangxi Provincial Key R&D Program. The review addresses the rapidly evolving landscape of PTA cladding materials, spanning from traditional metallic powders to advanced composite and functionally graded systems, and is particularly relevant to engineers seeking to select appropriate cladding materials for demanding corrosion and wear applications.

PTA Process Fundamentals for Cladding

Plasma transferred arc cladding operates by feeding a consumable powder through a plasma torch where the powder is melted by the high-temperature plasma jet (arc temperatures of 10,000–30,000 K) and deposited onto the substrate as a dilution-free or low-dilution overlay layer. The key advantages of PTA cladding over other overlay methods include:

The low dilution characteristic of PTA is the primary reason for its widespread adoption in aerospace, chemical processing, and power generation industries where the overlay composition must closely match the design specification.

Classification and Review of Cladding Materials

The review categorizes PTA cladding materials into several major groups:

Metallic Alloy Powders

• Stainless steel powders: 304, 316L, 321, 347 — used for general corrosion resistance in chemical and food processing equipment
• Nickel-based superalloy powders: Inconel 625, Inconel 718, Hastelloy C-276, Stellite 6 — used for high-temperature corrosion and erosion resistance in gas turbine components
• Copper-based powders: Cu-Cr, Cu-Ni (Monel 400) — used for electrical contact surfaces and marine applications

Composite Powder Systems

• WC-Co composites: WC particles (5–45 μm) in cobalt or nickel-cobalt matrix — the workhorse of abrasion-resistant cladding, with hardness reaching 1200–1600 HV
• Cr₃C₂-NiCr composites: Chromium carbide particles in nickel-chromium matrix — superior to WC-Co in corrosion-abrasion dual service
• TiC/TiN-reinforced composites: Ceramic particles in metallic matrix — emerging systems for high-temperature wear applications

Functionally Graded Materials (FGMs)

The review highlights the growing importance of functionally graded overlay designs where the powder composition is varied from pass to pass to create a compositional gradient from the substrate to the surface. For example, a typical FGM design for a chemical reactor lining might progress from a weldable transition layer (e.g., Ni-Fe) through a corrosion-resistant intermediate layer (e.g., Hastelloy C-276) to a wear-resistant surface layer (e.g., Cr₃C₂-NiCr composite).

Key Research Directions and Recent Advances

The review identifies several active research directions in PTA cladding materials:

1. High-entropy alloy (HEA) powders: Multi-principal element alloys such as CoCrFeMnNi deposited by PTA show exceptional combinations of strength, corrosion resistance, and radiation resistance, though commercial adoption is still in early stages.
2. Nano-structured powders: Pre-nanostructured or nano-reinforced powders (e.g., nano-TiC/Co, nano-SiC/Ni) deposited by PTA can retain some nanoscale features after rapid solidification, leading to hardness improvements of 20–40% over conventional micropowder deposits.
3. Reactive powder systems: Thermite-type composite powders (e.g., Al-Fe₂O₃, Ti-C) that undergo exothermic reactions during PTA deposition, generating additional heat and enabling deposition of reactive materials (TiC, TiB, TiN) without requiring the full plasma energy input.
4. Self-healing cladding materials: Incorporation of nano-encapsulated healing agents within the overlay microstructure that release upon crack initiation, representing a frontier concept with limited practical implementation to date.

Powder Quality and Process-Structure-Property Relationships

A critical aspect emphasized in the review is the relationship between powder characteristics and final cladding performance:

The review also discusses the importance of powder preheating and drying protocols, as well as the effect of powder feed rate on the dilution rate and microstructure of the deposited layer. Optimal powder feed rates are typically 300–600 g/min for standard PTA torches with 25–30 A/cm² current density.

Engineering Selection Guidelines

Based on the comprehensive review, the following selection guidelines are recommended for engineering practice:

• For general corrosion resistance in aqueous environments: 316L or Hastelloy C-276 powder, 3–5 passes, post-weld solution treatment at 1050°C for 316L or 1150°C for Hastelloy
• For high-temperature erosion-corrosion: Inconel 625 or Stellite 6, with consideration of thermal cycle effects on the base metal
• For severe abrasion: Cr₃C₂-NiCr composite powder with 40–50 vol% Cr₃C₂, 2–3 passes with dilution monitoring
• For dual corrosion-abrasion service: Functionally graded design with corrosion-resistant base passes and abrasion-resistant surface passes

This review serves as an indispensable reference for engineers specifying PTA cladding materials, providing both the fundamental understanding and the practical decision-making framework necessary for successful cladding system design.