Matrix Composite Coatings Deposited on AISI 4715 Steel by Powder Plasma-Transferred Arc Welding. Part 3. Comparison of the Brittle Fracture Resistance of Wear-Resistant Composite Layers Surfaced Using the PPTAW Method

Abstract

This article is the last of a series of publications included in the MDPI special edition entitled “Innovative Technologies and Materials for the Production of Mechanical, Thermal and Corrosion Wear-Resistant Surface Layers and Coatings”. Powder plasma-transferred arc welding (PPTAW) was used to surface metal matrix composite (MMC) layers using a mixture of cobalt (Co3) and nickel (Ni3) alloy powders. These powders contained different proportions and types of hard reinforcing phases in the form of ceramic carbides (TiC and WC-W2C), titanium diboride (TiB2), and of tungsten-coated synthetic polycrystalline diamond (PD-W). The resistance of the composite layers to cracking under the influence of dynamic loading was determined using Charpy hammer impact tests. The results showed that the various interactions between the ceramic particles and the metal matrix significantly affected the formation process and porosity of the composite surfacing welds on the AISI 4715 low-alloy structural steel substrate. They also affected the distribution and proportion of reinforcing-phase particles in the matrix. The size, shape, and type of the ceramic reinforcement particles and the surfacing weld density significantly impacted the brittleness of the padded MMC layer. The fracture toughness increased upon decreasing the particle size of the hard reinforcing phase in the nickel alloy matrix and upon increasing the composite density. The calculated mean critical stress intensity factor KIc of the steel samples with deposited layers of cobalt alloy reinforced with TiC and PD-W particles was 4.3 MPa⋅m12 higher than that of the nickel alloy reinforced with TiC and WC-W2C particles.

Influence of Preheating Temperature on Structural and Mechanical Properties of a Laser-Welded MMC Cobalt Based Coating Reinforced by TiC and PCD Particles

“…A higher content of matrix alloying additives and a higher proportion of hard phase ceramic particles reinforcing the composite contributed to an increase in abrasion resistance, but at the same time increased the tendency for surface cracks to form in the padding weld. Cracks appeared during cooling due to the difference in the thermal expansion coefficients of the base material and the padding weld material [37]. The cracks most often penetrated deep into the base material and in no way weakened the adhesion of the surface coating.…”

Hardfacing of mild steel with wear-resistant Ni-based powders containing tungsten carbide particles using powder plasma transferred arc welding technology

“…The current state of PPTAW provides insight into how PGFR is a major contributing factor to the resultant mechanical properties of the hardfaced layer [21,26]. The present research studies the effects of PGFR on the hardfaced layers' microstructure, hardness, abrasive wear resistance, and crack formation and propagation.…”

“…The relative abrasive wear resistance was computed against that of the reference material, AR400. This material was selected as the reference material based on its proven resistance to abrasive wear as well as its repeated use in other research works [7,18,21,22] for similar such investigations. The average volume loss and the effects of PGFR on the abrasive wear resistance of the tested samples are presented in Figure 12.…”

Hardfacing of mild steel with wear-resistant Ni-based powders containing WC particles using PPTAW technology

“…The current state of PPTAW provides insight on how plasmas gas flow rate (PGFR) is a major contributing factor to the resultant mechanical properties of the hardfaced layer [18,19]. In this study, the effects of PGFR on the microstructure, hardness, abrasive wear resistance, crack formation and propagation, of the hardfaced layers were studied.…”