(1) Background: Boron-based diffusion layers possess great application potential in forging and die-casting due to their favorable mechanical and thermophysical properties. This research explores the enhanced wear resistance of tungsten hot-work steel through boriding and boroaluminizing. (2) Methods: Thermal-chemical treatment (TCT) of steel H21 was carried out. Pure boriding was introduced to the substrate through heating a paste of boron carbide and sodium fluoride 1050 °C for two hours. As for boroaluminizing, 16% of aluminum powder was added to the boriding paste. (3) Results: It was shown that boriding resulted in the formation of an FeB/Fe₂B layer with a tooth-like structure. A completely different microstructure was revealed after boroaluminizing—namely, diffusion layer with heterogeneous structure, where hard components FeB and M_x (B,C) were displaced in the matrix of softer phases—Fe₃Al and α-Fe. In addition, the layer thickness increased from 105 μm to 560 μm (compared to pure boriding). The maximum microhardness values reached 2900 HV0.1 after pure boriding, while for boroaluminizing it was about 2000 HV0.1. (4) Conclusions: It was revealed that the mass loss during wear test reduced by two times after boroaluminizing and 13 times after boriding compared to the hardened sample after five-min testing.

The article describes the research results of steel C30 boroaluminised by isothermal and thermocycle methods in powder mixtures. Thermocycling is performed in the range of 650–950°C. In this study, a comparative analysis of microstructure, composition of elements and microhardness of boroaluminised steels after various treatments is presented. A series of tensile tests and a plasticity estimation of boroaluminised layer were carried out.

(1) Background: Operational properties and durability of dies in different metal-forming processes significantly depend on their surface quality. Major die failures are related to surface damage due to heat checking cracks, wear, etc. Thereby, strengthening of the working surfaces of dies for hot bending, stamping, forging, and die casting processes is an urgent engineering challenge. Surface alloying with high-energy beams improves the properties of steel products. In these processes, the alloying powders and the treated surfaces can be remelted by electron beam within a short time while the bulk structure of the component remains unchanged, resulting in minimal distortion. The paper presents the results of the electron beam surface alloying (EBSA) of H21 and L6 tool steels with the treatment pastes containing boron carbide and aluminum powders. (2) Methods: Two types of pastes were used for surface alloying: a single-component (B₄C) paste and a two-component (B₄C+Al) one. The microstructure, microhardness, wear resistance, and elemental and phase composition of the layers obtained on steels were investigated. (3) Results: Four layers up to 0.4 mm thick were distinguished on the surface of the steels after the EBSA. Metallographic analysis showed coarse dendrite formation in the layers embedded in matrices of a eutectic or a solid solution. Microhardness of the steels after the two-component EBSA was higher than after B₄C EBSA, which was related to a higher concentration of hard phases, such as iron borides and carbides. In addition, aluminum boride was revealed by the XRD analysis on L6 steel after B₄C+Al EBSA. (4) Conclusions: Wear test indicated that the most resistant samples were H21 steel after single B₄C EBSA and L6 steel after B₄C+Al EBSA. Both samples contained carbon particles in the layer contributing to the high wear resistance as a lubricant. The conducted research is beneficial for mechanical engineering, automotive engineering, medical technology, aerospace engineering, and related industries, where coatings with high microhardness, wear resistance, and surface quality are demanded.

This article investigates the possibility of improving the wear resistance of carbon steel 30 by means of boroaluminizing in treatment pastes. Boroaluminizing was conducted in sodium fluoride (as an activator), boron carbide, and aluminum at furnace heating (the latter two components were taken in a ratio of 4 to 1). The treatment was administered for 4 hours in four temperature modes between 950°C and 1,100°C with a 50°C difference between modes. The microstructure, microhardness, and elemental and phase compositions of the boroaluminized layers were investigated. In addition, the wear resistance of the boroaluminized steels was tested. It was established that treatment temperatures of 1,000°C and lower lead to the formation of layered structures consisting of iron aluminides that are mainly located on top of the diffusion layer and iron borides adjacent to the base metal. Moreover, the use of boroaluminizing temperatures over 1,000°C results in the formation of a heterogeneous structure with iron borides FeB and Fe2B evenly distributed in the matrix of aluminum solid solution in iron. This contributes significantly to the mechanical properties of the layer; in particular, it enhances its wear resistance. It was established that the wear resistance of steel 30 significantly improves after treatment at 1,100°C in comparison with temperature modes of 950°C and 1,000°C.

(1) Background: Boriding is one of the most common methods of thermal-chemical treatment due to its excellent hardness and wear resistance of the produced diffusion layers. However, it has limited application compared to carburizing and nitriding because of fragility and chipping. Introducing another alloying element into the boron media helps avoid those drawbacks and improve other surface properties of the layer. The purpose of this work is to improve the surface mechanical properties of L6 and 5140 low alloy steels by two-component surface hardening with boron and copper. (2) Methods: The treatment was performed by means of a powder-pack method using boron, copper, and aluminum powders in the following proportions: 60% B₄C + 20% Al₂O₃ + 16% CuO + 4% NaF. The time–temperature parameters of the treatment were four hours exposure at 950 °C. Microstructure, elemental, and phase composition were investigated as well as microhardness and wear resistance of the obtained layers. (3) Results: Layers of up to 180–200 μm thick are formed on both steels as a result of treatment. Needle-like structures similar to pure boriding was obtained. The maximum microhardness was 2000 HV on L6 steel and 1800 HV on 5140 steel. These values correspond to iron borides and were confirmed by XRD analysis revealing FeB, Fe₂B, and Cr₅B₃. The wear resistance of both steels was about ten times higher after the treatment compared to non-treated samples. (4) Conclusions: Surface hardening with boron and copper significantly improves the mechanical properties of both alloy steels. The results obtained are beneficial for different tribo-pair systems or three-body wear with abrasion and minimum impact loads.