A different attempt to investigate the influence of PTA parameters on microstructure evolution and mechanical characteristics of nickel base powder (Ni-WC) deposited tool steel

Abstract

The impact of joining parameters, namely preheat, current, and travel speed, due to the crack formation susceptibility of D2 steel during the deposition process, is crucial to achieve weld bead geometries with acceptable metallurgical and mechanical properties. Therefore, the main purpose of the current article is to optimize welding parameters to obtain a sufficient hardfaced coating of nickel-base powder combined with tungsten carbide on the tool steel by the plasma transferred arc (PTA) process with the help of the Design of Experiment (DoE) method. To analyze the properties of the welding beads, scanning electron microscopy (SEM) accompanied by EDS, optical microscopy (OM), XRD analysis, microhardness, and nano-indentation methods on the samples were applied. The results indicated that there is adequate adhesion and continuous bonding between areas due to improved interactions between hard particles and matrix which leads to a reduction in the porosity of the composite coatings. According to the obtained results, the optimized parameters (current, travel speed, and preheating temperature) for uniform distribution of reinforcing particles and high mechanical properties are 86 A, 85 cm/min, and 1350 °C, respectively. Based on optical profilometry analysis on the surface of the samples, there is high homogeneity in reinforcing distribution. The nanoindentation analysis detected three prominent phases, including FeNiCr dendritic matrix phase, large WCrC (carbide) phase, and mono tungsten carbide WC phase. The obtained results improve the length of the tool's service life and an economic fabrication with decreased unit costs.