Microstructure and Erosion Wear of In Situ TiC-Reinforced Co-Cr-W-C (Stellite 6) Laser-Cladded Coatings.

The article presents research results on the possibility of shaping the structure and properties of Co-Cr-W-C-Ti alloys (type Stellite 6) using laser cladding technology. Cobalt-based alloys are used in several industries because they are characterized by high erosion, abrasion, and corrosion resistance, retaining these properties at high temperatures. To further increase erosion resistance, it seems appropriate to reinforce material by in situ synthesis of hard phases. Among the transition metal carbides (TMCs), titanium carbide is one of the hardest and can have a positive effect on the extension of the lifetime of components made from cobalt-based alloys. In this article, concentration of C, W, and Ti due to the possibility of in situ synthesis of titanium carbides was subjected to detailed analysis. The provided research includes macrostructure and microstructure analysis, X-ray diffraction (XRD), microhardness, and penetrant tests. It was found that the optimal concentrations of Ti and C in the Co-Cr-W-C alloy allow the formation of titanium carbides, which significantly improves erosion resistance for low impact angles. Depending on the concentrations of titanium, carbon, and tungsten in the molten metal pool, it is possible to shape the alloy structure by influencing to morphology and size of the reinforcing phase in the form of the complex carbide (Ti,W)C.

High-Temperature Corrosion of Flame-Sprayed Power Boiler Components with Nickel Alloy Powders.

The development trends in the energy sector clearly indicate an increase in the share of biomass and alternative fuels fed for combustion in power boilers, which results in the imposition of many unfavourable factors and a demanding working environment. During the operation of the energy system, this means a sharp increase in corrosion of the gas-tight pipe walls and coils by the destructive action of chlorine and sulphur. Implementing advanced surface protection in addition to the selection of materials of better quality and resistance to difficult working conditions would significantly reduce their wear by high temperature corrosion. Thermally sprayed coatings offer a great opportunity to protect machine components and energy systems against corrosion, erosion, impact load and abrasive wear. This article presents the test results of high-temperature corrosion resistance of coatings made with Ni-Cr-B-Si and Ni-B-Si alloy powders on a boiler steel substrate. Samples with sprayed coatings were exposed to an atmosphere with a composition of N2 + 9% O2 + 0.08% SO2 + 0.15% HCl at 800 °C for 250, 500, 750 and 1000 h. Tests results of coatings made of Ni-Cr-B-Si alloys subjected to the influence of a corrosive environment showed the formation of a layer of scale on the surface, composed mainly of Cr2O3 oxide, which was a passive layer, reducing the rate of corrosion. Coatings sprayed with Ni-B-Si alloys showed significantly lower corrosion resistance. It was found that the developed technology of subsonic flame spraying with powders of the Ni-Cr-B-Si type allows the production of coatings compliant with the requirements of the energy industry, which allows their use as anti-corrosion protection on boiler elements intended for waste disposal and biomass combustion.

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.

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.

Properties and Structure of Deposited Nanocrystalline Coatings in Relation to Selected Construction Materials Resistant to Abrasive Wear.

Presented in this work are the properties and structure characteristics of MMA (Manual Metal Arc) deposited nanocrystalline coatings (Fe-Cr-Nb-B) applied to an iron nanoalloy matrix on an S355N steel substrate in relation to selected construction materials resistant to abrasive wear currently used in industry. The obtained overlay welds were subjected to macro and microscopic metallographic examinations; grain size was determined by X-ray diffraction (XRD), and chemical composition of precipitates was determined by energy-dispersive X-ray spectroscopy (EDS) during scanning electron microscopy (SEM). The size of the crystalline grains of the Fe-Cr-Nb-B nanocrystalline microstructure was analyzed using an Xpert PRO X-ray diffractometer. Analysis of the test results of the obtained layers of arc-welded Fe-Cr-Nb-B-type alloy confirmed that the obtained layers are made of crystallites with a size of 20 nm, which classifies these layers as nanocrystalline. The obtained nanocrystalline coatings were assessed by hardness and with the use of metal-mineral abrasion testing. The results of the coatings' properties tests were compared to HARDOX 400 alloy steel.

Assessment of the Surgical Treatment Results in Patients with Colorectal Cancer in a District Hospital Versus Treatment Results in a Highly Specialized Center.

UNLABELLED: In Poland there there are about 15-16 thousand cases of colon cancer per year. The health care system allows the treatment of patients with colorectal cancer in highly specialized hospitals, oncology centers and district hospitals. The results of treatment within different reference level differ. The aim of the study was to evaluate the results of surgical treatment of patients with colorectal cancer at a district hospitals compared with the results of highly specialized center. MATERIAL AND METHODS: A retrospective study. The material consisted of 171 consecutively operated patients diagnosed with colorectal cancer treated in the Department of Surgery, District Hospital in Wolomin. The control group consisted of 200 patients treated surgically at the Department of General and Colorectal Surgery, University Hospital in Lódz. In both centers, the patients were operated on by surgeons with experience in operations on the large bowel. The demographic data, information on the type of indication (elective vs emergent), and the severity of the disease by AJCC / TNM scale were collected. In the district hospital there were patients with more advanced disease (p <0.001), older (p = 0.0001), and often operated under emergent indication (p = 0.0001). The telephone survey collected data on survival or the date of death of the patient and set the percentage of five-year survival. RESULTS: The proportion of five-year survival in the study group and control group was respectively 46% and 71% (p <0.0001). The percentage of five-year survival among patients undergoing elective procedure in both centers were respectively for Wolomin and Lódz 58% and 73% (p = 0.008). The proportion of 5-year survival among "younger" patients (<70) was respectively in Wolomin and Lódz 64% and 81% (p = 0.004) for "older" patients with (> 70) 50% and 60% (p = 0.6747) Conclusions. Overall results of surgical treatment of patients with colorectal cancer in the district hospital are inferior to treatment results in a highly specialized center. The population treated in the district hospital is statistically significantly different in comparison to patients treated in highly specialized center. The following differences were captured: severity of the disease, age and type of indication (elective vs emergent). The diffrences has an influence on the outcomes. The five years survival for patients > 70 years undergoing elective procedure is not statistically different between the district hospital and highly specialized center.