TIG Cold Welding Remelting and Wire Deposition on 1Cr17 Stainless Steel Surface

Literature Overview

This 2021 study by Zheng Shao-Xian, Wang Jun-Ping, Yang Mei-Juan, and E Xin from Lanzhou Jiaotong University investigates a novel TIG cold welding technique for surface modification of 1Cr17 ferritic stainless steel. Published in Mechanical Engineering Materials (Vol. 45, No. 12, pp. 42-48), the research was supported by the National Natural Science Foundation of China (Grant No. 51765030) and the Gansu Provincial Natural Science Foundation (Grant No. 20JR5RA416). The work addresses two distinct surface engineering applications: remelting of the base metal surface and deposition of ER347L stainless steel wire.

Core Technical Concept

The TIG cold welding technique described in this study employs a unique approach: a very short-duration, high-current TIG arc is applied to the workpiece surface for a precisely controlled time interval. The term "cold welding" here refers to the fact that the heat input is so localized and brief that the base metal remains largely at ambient temperature, with melting confined to a very thin surface layer.

Process Parameters

Parameter	Remelting Process	Wire Deposition Process
Cold weld time range	50-200 ms	50-200 ms
Minimum current at 200 ms	40 A	120 A
Minimum current at 150 ms	70 A	150 A
Minimum current at 100 ms	100 A	190 A
Minimum current at 50 ms	100 A	230 A
Filler metal (deposition)	N/A	ER347L stainless steel wire

The inverse relationship between cold weld time and minimum current is physically intuitive: shorter exposure times require higher currents to achieve the same melting depth.

Microstructural Analysis

Heat-Affected Zone Characteristics

One of the most significant findings is the minimal effect of the cold welding process on the base metal microstructure:

Feature	Base Metal (1Cr17)	HAZ (after cold welding)
Grain size	Normal ferritic structure	No significant coarsening
HAZ width	N/A	≤ 250 μm
Phase composition	Ferrite + minor carbides	Unchanged

The HAZ width of 250 μm or less is remarkably narrow, indicating extremely limited thermal diffusion into the base metal. This is a direct consequence of the very short arc duration and high current density.

Remelting Layer and Deposition Layer Characteristics

Property	Base Metal	Remelting Layer	Deposition Layer (ER347L)
Grain size	Coarse	Fine	Fine
Hardness	Lower	Higher	Higher
Corrosion resistance (3.5% NaCl)	Baseline	Improved	Improved

The refinement of microstructure in both the remelting and deposition layers is attributed to the rapid solidification rates achieved with the short-duration arc. The high cooling rates promote nucleation and inhibit grain growth, resulting in a fine-grained microstructure with improved mechanical and corrosion properties.

Corrosion Performance Evaluation

The electrochemical corrosion testing in 3.5% NaCl solution provides quantitative evidence of the surface modification effectiveness:

The remelting layer exhibits improved corrosion resistance compared to the base metal
The ER347L deposition layer shows the best corrosion performance
The improvement is attributed to:
Fine-grained microstructure reducing active corrosion sites
Homogeneous distribution of alloying elements in the remelted/deposited layer
Potential for enhanced passive film formation on the refined surface

Engineering Application Analysis

Application Scenarios

This TIG cold welding surface modification technique is applicable to several important engineering scenarios:

Repair of worn surfaces: Restoration of dimensional accuracy on worn 1Cr17 stainless steel components without significant heat distortion
Corrosion resistance enhancement: Surface modification of existing components to extend service life in corrosive environments
Local hardening: Improvement of surface hardness without affecting the bulk mechanical properties
Pre-weld surface preparation: Surface cleaning and activation before subsequent welding operations

Process Advantages Over Conventional Methods

Method	HAZ Width	Distortion	Application Rate	Equipment Complexity
Conventional TIG welding	> 1 mm	Significant	Moderate	Low
Laser remelting	0.1-0.5 mm	Minimal	High	High
TIG cold welding (this study)	≤ 0.25 mm	Minimal	Moderate	Moderate
Flame hardening	> 2 mm	Significant	Low	Low

The TIG cold welding approach offers a favorable balance between process effectiveness and equipment accessibility, making it suitable for field applications and repair work where laser systems may not be available.

Critical Reflection

Several aspects of this research merit further consideration for engineering implementation:

Process repeatability: The precise control of arc duration (50-200 ms) requires specialized power supply control. The consistency of results across multiple applications needs validation.
Surface quality: The morphology of the remelting and deposition layers was described as "well-formed," but quantitative surface roughness measurements would be valuable for specific applications.
Multi-pass capability: The study focuses on single-pass applications. The feasibility of building up thicker layers through multiple passes with controlled interpass temperatures requires investigation.
Cost-effectiveness: Compared to conventional welding repair methods, the additional equipment investment for precise time-controlled TIG welding needs economic justification.

Study Insights

The fundamental contribution of this research is demonstrating that extremely short-duration, high-current TIG welding can achieve surface modification with minimal thermal impact on the base metal. The HAZ width of 250 μm or less is comparable to laser processing results but achievable with more accessible and affordable equipment. For maintenance and repair engineers working with 1Cr17 stainless steel piping and components, this technique offers a practical means of surface improvement without the risk of thermal distortion or microstructural degradation that plagues conventional welding repair methods.