Plasma Transferred Arc Welding Research Articles

Effect of alloy modification on the wear protection coatings made of Ni- and Co-based materials and surface machinability via ultrasonic milling process

Wear-resistant coatings are required for highly efficient and economical steel components in equipment, process, and power plant engineering to withstand high corrosive, tribological, thermal, and mechanical stresses. Co-alloys are used as wear-resistant coatings for steel components, tailored to the specific application. The substitutability of Co alloys with Ni-based wear protection systems, in addition to price and supply uncertainties, is facilitated by the combination of innovative welding and machining processes such as ultrasonic-assisted milling. The aim of the study is to improve the machinability of two different hard-facing alloys while maintaining the same wear protection potential. Therefore, the wear-resistant alloys NiMoCrSi (Colmonoy C56) and CoMnCrSi (Tribaloy T400) were modified by the alloying additions Nb, Hf, and Ti and then applied to a carbon-manganese steel S355 using the plasma transfer arc (PTA) welding process. The influence of the alloying additions on the microstructure as well as on the formation of the hard phases of the build-up welds is compared. For example, the inclusion of the alloying element Nb results in the formation of a more refined hard phase and reduces the machining force required for C56 and T400. In most cases, the wear resistance potential has been maintained. In order to improve the machinability of the hard facings, the optimization of the demanding machining conditions by alloy modifications of the Co- and Ni-based alloys is also presented. It is shown that some of the modified alloys have significantly better machinability than the conventional alloy.

INVESTIGATIONS ON HARDFACING CHARACTERISTICS OF NI-BASED ALLOY ON ASS 304 USING PLASMA TRANSFERRED ARC WELDING AT DIFFERENT SPEEDS

AISI 304 stainless steel is one of the most commonly used austenitic steel in various industries such as petro-chemical, nuclear plant, food, bio-medical, due to its desirable bulk mechanical properties such as high toughness, corrosion resistance, etc. However, it lacks the surface properties such as wear resistance and hardness which is critically required in severe working conditions. Hardfacing is an effective method to increase the surface properties, without disturbing the bulk mechanical characteristics. Among other coating techniques such as MIG, FCAW, laser cladding and so on, Plasma transferred arc welding can be considered superior in terms of bond strength, controlled dilution and high deposition rate. Due to the formation of high hardness and wear resistance coating quality, single layered Ni-Cr-B-Si alloy is coated over AISI 304 using plasma transferred arc welding process in present work. Among various process parameters, travel speed directly affects the rate of heat input and rate of overlay deposition which determines the cooling rate which influences microstructure, coating thickness and dilution. In this work, effect of travel speed was observed on coating microstructure, microhardness, wear resistance and dilution. Slurry abrasive wear test was performed to evaluate the wear resistance of the coating, by measuring the weight loss at various travel speed. Wear resistance was observed to be improved by a factor of about 4 as compared to the substrate material which shows a decreasing trend as we increase the travel speed. The microhardness of the coating was observed to go as high as 500 HV for certain travel speed. Dilution was observed to be ranging between 18% to 32% which increases with travel speed because of low heat input at higher travel speed. The microstructure investigation shows formation of a dendritic structure of borides and carbides, which was concluded to be the reason behind the obtained high hardness. Formation of Ni- γ phase was also observed on the top layer of the coating microstructure.

Target Alloys of Iron-Based Materials through CALPHAD Method

The development of tailored alloys is an important aspect for enhancing efficiency across diverse applications in mechanical engineering. The use of computer-aided modelling offers an opportunity to enable a more efficient and targeted material development. In the present work, new iron-based alloys with specific properties were developed using the CALPHAD method. The alloy design developing process was carried out by using the simulation software JMatPro® and the data evaluation software EDA®. Using a full factorial plan, various alloys were modelled on the basis of the elements iron, nickel, vanadium, carbon, niobium and chromium. Afterwards, the alloys were narrowed down with regard to the criteria of carbide phase content, formability, and corrosion resistance. Subsequently, two final alloys were chosen based on their properties. Afterwards the selected final alloys were produced by mechanically blending different powder alloys and elements. These alloys were welded onto unalloyed steel using Plasma Transferred Arc welding and were characterised by using x-ray diffraction, scanning electron microscopy, hardness measurements, spark spectrometry and metallography. Subsequently, a verification of the welded samples regarding to chemical composition, phases, and corrosion resistance was carried out. The investigations showed that it was possible to simulate alloys with specific properties using computer-based software, which corresponded with the experimental studies.

Research on Ni-WC Coating and a Carbide Solidification Simulation Mechanism of PTAW on the Descaling Roll Surface

The descaling roll is a critical component in a hot-rolling production line. The operating conditions are significantly impacted by water with high-pressure and dynamic shocks caused by high-temperature steel slab descaling. Roll surfaces often experience wear and corrosion failures. This is attributed to a combination of high temperatures, intense wear, and repeated thermal, mechanical, and fluid stresses. Production costs and efficiency are significantly affected by the replacement of descaling rolls. Practice shows that the use of plasma cladding technology forms high-performance coatings. Conventional metal surface properties can be significantly improved. In this study, a Ni-WC composite coating was prepared on the descaling roll surface by plasma-transferred arc welding (PTAW) technology. The microstructure and phase composition of the welding overlay were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that the WC hard phase added to the molten pool dissolves, and subsequently M7C3 and W2C phases are formed. To further explore the morphological evolution mechanism of the hard phase, numerical simulations were performed using a phase-field method to model M7C3 phase precipitation. The evolution from nucleation, rod-like growth, to eutectic structure formation was revealed. Experimental and simulation results show high consistency, validating the established phase-field model. In this study, a theoretical foundation for designing and preparing high-performance coatings is provided.

Effect of Main Arc Current on Microstructure and Cavitation Resistance of NiCrBSi-WC Alloy Coating Prepared by Plasma Transfer Arc Welding

Effect of Main Arc Current on Microstructure and Cavitation Resistance of NiCrBSi-WC Alloy Coating Prepared by Plasma Transfer Arc Welding

Effects of Long-Time Thermal Exposure on Microstructure Evolution in T-400C Hardfacing Deposited on Haynes 282 via Plasma Transferred Arc Welding

Effects of Long-Time Thermal Exposure on Microstructure Evolution in T-400C Hardfacing Deposited on Haynes 282 via Plasma Transferred Arc Welding

Impact abrasive wear of tungsten carbide reinforced NiBSi coating fabricated by plasma transferred arc welding

Impact abrasive wear of tungsten carbide reinforced NiBSi coating fabricated by plasma transferred arc welding

Effect of powder composition, PTAW parameters on dilution, microstructure and hardness of Ni–Cr–Si–B alloy deposition: Experimental investigation and prediction using machine learning technique

The implementation of hard-facing alloy on the existing materials caters the need for high-performance surfaces in terms of wear and high temperatures. The present research explore the effect of Plasma Transferred Arc Welding (PTAW) parameters and powder composition on dilution, microstructure and hardness of the commonly used hard-facing alloy Ni-Cr-Si-B powder. The hard-facing alloy was deposited with three weight proportions of boron (2.5 %, 3% and 3.5%). The statistical-based Grey Relational Analysis (GRA) followed by a Machine Learning Algorithm (MLA) was implemented to identify the ideal parameters and degree of significance of each parameter and for the prediction of the responses. The dilution percentage, microstructure analysis, and phase detection were estimated through elemental analysis, Scanning electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD) respectively. The experimental and modelling results revealed that 400mm/min of scanning speed, 8gm/min of powder delivery, 14mm of stand-off distance, and 120 A of current were the optimal parameters along with 3.5wt% of boron powder composition to yield a better dilution, microstructure and hardness.

Study of the Microstructure and Hardness of an H13 Steel Bead by Plasma Transferred Arc Welding

Study of the Microstructure and Hardness of an H13 Steel Bead by Plasma Transferred Arc Welding

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

Thermal-induced evolution of microstructure as a plasma arc coating Direction-Dependent phenomenon

Thermal-induced evolution of microstructure as a plasma arc coating Direction-Dependent phenomenon

Effect of pool temperature on microstructure and corrosion resistance of PTAW Ni layer

Effect of pool temperature on microstructure and corrosion resistance of PTAW Ni layer

Effect of HVOF spray coating on the tribological surface of onshore gate valves

Effect of HVOF spray coating on the tribological surface of onshore gate valves

Microstructure and performance of NiCrBSi coatings prepared by modulated arc currents using powder plasma transferred arc welding technology

Microstructure and performance of NiCrBSi coatings prepared by modulated arc currents using powder plasma transferred arc welding technology

The Effect of Niobium on <i>In Situ</i> Synthesis of Titanium Carbide in Composite Hardfacings

Niobium (Nb) and titanium (Ti) react with carbon to form high-melting-point and high-hardness MC-type carbides. This study explores the in-situ synthesis of mixed NbC-TiC carbides during plasma transferred arc welding of a steel-based hardfacing. Feedstock powders consisted of stainless steel AISI 316L, TiO2, and graphite with and without 5 wt.% Nb addition. Feedstock powders were ball milled for 72 hours, then mixed with paraffine and pre-placed on the S235 steel. The cladding current was 125 A, and the plasma torch travel velocity was 1 mm/s and 0.7 mm/s. The effect of Nb on TiC generation was examined using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS). Vickers hardness was also measured at the surface of hardfacings. Results show that previously formed NbC grains acted as nucleation sites for TiC precipitation. Increased torch velocity has resulted in improving distribution and decreasing agglomeration of carbon phases. Hardness tests showed that Nb and Ti increased the hardness resistance of the substrate steel.

Effect of mating material on wear behaviour of Ni-based hardface coating

The selection of tribopairs, including mating materials, plays a crucial role in controlling material loss under rubbing conditions. In a fast breeder nuclear reactor, almost all moving components have been provided with a hardfaced coating at the mating surfaces for their longer life. Though, in most cases, the hardfaced surfaces come into contact with the components having the same coating; in some instances, they are allowed to rub against other materials. In the present investigations, an effort was made to study the wear behaviour of a Ni-based hardfaced coating made on 316LN stainless steel under similar and dissimilar mating conditions. Prior to wear tests, a defect-free hardface coating of Ni-based hardfacing alloy was made on 316LN stainless steel using plasma transferred arc welding process and subsequently characterized for its microstructure and hardness. Wear tests under dry sliding conditions were carried out at ambient temperature. The specific wear rate for dissimilar mating conditions was found to be one order of magnitude higher than the same rate obtained from similar mating conditions. Moreover, adhesive wear was the dominant wear mechanism in both mating conditions. It is clear from the study that similar material combinations should be given preference in the design of tribopairs instead of dissimilar material combinations to avoid significantly higher material losses for materials with lower hardness. The reported results will provide insight for carefully designing the tribopairs for critical applications.

Experimental Comparison of Laser Cladding and Powder Plasma Transferred Arc Welding Methods for Depositing Wear-Resistant NiSiB + 60% WC Composite on a Structural-Steel Substrate.

A Ni-based powder composed of NiSiB + 60% WC was deposited onto a structural-steel substrate using two methods: laser cladding (LC) and plasma powder transferred arc welding (PPTAW). The resulting surface layers were analyzed and compared. Both methods resulted in the precipitation of secondary WC phases in the solidified matrix, but the PPTAW clad exhibited a dendritic microstructure. The microhardness of the clads prepared by both methods was similar, but the PPTAW clad showed higher resistance to abrasive wear compared to the LC clad. The thickness of the transition zone (TZ) was thin for both methods, with a coarse-grain heat-affected zone (CGHAZ) and peninsula-like macrosegregations observed in clads from both methods. The PPTAW clad showed a unique cellular-dendritic growth solidification (CDGS) and a type-II boundary at the TZ attributed to its thermal cycles. While both methods resulted in metallurgical bonding of the clad to the substrate, the LC method exhibited a lower dilution coefficient. The LC method also resulted in a larger HAZ with higher hardness compared to the HAZ of the PPTAW clad. The findings of this study indicate that both methods are promising for antiwear applications due to their wear-resistant properties and metallurgical bonding to the substrate. The PPTAW clad may be particularly useful in applications that require higher resistance to abrasive wear, while the LC method may be advantageous in applications that require lower dilution and larger HAZ.

Design and performance of nitrogen-alloyed iron-based coating for enhancing galling resistance by plasma transferred arc welding

Iron-based alloys have been widely used as high-temperature galling resistant coatings. In this study, we designed and prepared a galling-resistant coating using plasma transferred arc welding with cored wires of varying nitrogen content. Our approach was based on the concept that nitrogen alloying can lead to the formation of hard precipitates and promote strain-induced phase transformations. The coating was primarily composed of austenite, and as the nitrogen content increased, the grain size decreased and the amount of nitride precipitation increased. The threshold galling stress of this cobalt-free coating was found to reach 80% of that of a laser-clad Stellite 21 coating at 300 °C. Following the galling test, the hardness of the worn area increased and a phase transformation from austenite to martensite occurred beneath the worn surface. The improvement in galling resistance under dry heavy load sliding conditions can be attributed to the synergistic effect resulting from multiple strengthening mechanisms, including fine-grain strengthening, second phase strengthening and phase transformation strengthening.

PTA-Welded Coatings with Saturation Magnetization above 1.3 T Using FeCrBSi Powders with Chemical Composition Similar to AISI 430 Ferrite Stainless Steel

Fe-Cr-based soft magnetic alloy (SMA) monolayer coatings with high saturation magnetization (Ms) above 1.3 T were deposited onto AISI 1010 substrate by co-axial powder feeding plasma transferred arc (PTA) welding, using FeCrBSi self-fluxing powders Fe313, which have a similar chemical composition to AISI 430 ferritic stainless steel (FSS). The effect of welding parameters on the phase assemblage, microstructure, hardness and magnetic performance of the coatings was investigated. The results show that the coating’s maximum width and the welding surplus height increased with the rise in welding heat input and powder distribution density, respectively. The coating’s Ms increased sharply, but its coercivity (Hc) decreased with the growth in the substrate dilution ratio. The coating’s Hc increased whereas its Ms decreased with the increment in welding heat input. The as-welded coating C3 with optimum magnetic performance had a dendrites–eutectics composite structure, where the columnar or equiaxed sorbitic pearlite dendritic cores surrounded by network-like eutectics α(Fe,Cr) + (Fe1−xCrx)2B were the main contents. Moreover, (Fe,Cr)7C3 and CrB had also been detected, and they were mainly distributed in the interdendritic regions. The body-centered cubic (b.c.c.) α(Fe,Cr) multi-element solid solution contributes to a high Ms of 1.61 T, and the borides (Fe1−xCrx)2B and CrB as well as (Fe,Cr)7C3 and other carbides cause a high Hc of 58.6 Oe and hardness HV0.3 of 4.90 ± 0.06 GPa, much higher than that of AISI 430 FSS (HV < 1.8 GPa). The current work verifies the feasibility of fabricating Ni- and Co-free FeCrBSi SMA coatings with high Ms and high hardness via PTA welding, and since the feedstock powders have chemical composition similar to AISI 430 FSS, the work may bring about novel applications for AISI 430 FSS in particular cases where the considerable wear-resistant performance as well as superior soft magnetic and anti-corrosive properties are required.

Tribological investigation of contact pairs applied in metallic gate valve seals for onshore application

Tribological investigation of contact pairs applied in metallic gate valve seals for onshore application