Progressive Loading Research Articles

Effects of oral HPΒCD-angiotensin-(1-7) supplementation on recreational mountain bike athletes: a crossover study

ABSTRACT Background Supplementation with Angiotensin-(1-7) [(Ang-1-7)] has received considerable attention due to its possible ergogenic effects on physical performance. The effects of a single dose of Ang-(1-7) on the performance of mountain bike (MTB) athletes during progressive load tests performed until the onset of voluntary fatigue have previously been demonstrated. This study tested the effects of Ang-(1-7) in two different exercise protocols with different metabolic demands: aerobic (time trial) and anaerobic (repeated sprint). Methods Twenty one male recreational athletes were given capsules containing an oral formulation of HPβCD-Ang-(1-7) (0.8 mg) and HPβCD-placebo (only HPβCD) over a 7-day interval; a double-blind randomized crossover design was used. Physical performance was examined using two protocols: a 20-km cycling time trial or 4 × 30-s repeated all-out sprints on a leg cycle ergometer. Data were collected before and after physical tests to assess fatigue parameters, and included lactate levels, and muscle activation during the sprint protocol as evaluated by electromyography (EMG); cardiovascular parameters: diastolic and systolic blood pressure and heart rate; and performance parameters, time to complete (time trial), maximum power and mean power (repeated sprint). Results Supplementation with an oral formulation of HPβCD-Ang-(1-7) reduced basal plasma lactate levels and promoted the maintenance of plasma glucose levels after repeated sprints. Supplementation with HPβCD-Ang-(1-7) also increased baseline plasma nitrite levels and reduced resting diastolic blood pressure in a time trial protocol. HPβCD-Ang-(1-7) had no effect on the time trial or repeat sprint performance, or on the EMG recordings of the vastus lateralis and vastus medialis. Conclusions Supplementation with HPβCD-Ang-(1-7) did not improve physical performance in time trial or in repeated sprints; however, it promoted the maintenance of plasma glucose and lactate levels after the sprint protocol and at rest, respectively. In addition, HPβCD-Ang-(1-7) also increased resting plasma nitrite levels and reduced diastolic blood pressure in the time trial protocol. Trial registration RBR-2nbmpbc, registered January 6th, 2023. The study was prospectively registered.

Characterization of bulk metallic glasses by microscratch test under Rockwell C diamond indenter and progressive normal load

Microscratch responses of 14 bulk metallic glasses were investigated by Rockwell C diamond indenter under progressive normal load. Effects of mechanical properties on microscratch variables are quantified for bulk metallic glasses. Penetration depth increases linearly with normal force, and a power-law function can be used to express the variation of residual depth with normal force under small loads. Residual depth fluctuates under large loads; and elastic recovery rate, scratch friction coefficient, lateral hardness, and scratch hardness all tend to be stable under large loads. The asymptotic scratch friction coefficient decreases linearly with the increase in scratch hardness. The asymptotic elastic recovery rate is found to be proportional to the ratio of elastic modulus over Knoop hardness, and scaling relationships among hardness values and yield strength are found. Different scratch-based methodologies of assessing fracture toughness are compared and discussed. The successful characterization of fracture toughness by scratch-based methods requires sufficiently large loads, and different methodologies have different scopes of application.

Bone stress injuries

Bone stress injuries, commonly referred to as stress reactions or stress fractures, are caused by overuse and are prevalent conditions in athletes. These injuries are often seen in sports with high cumulative skeletal loading such as running, athletics, gymnastics, basketball, cricket, or soccer. The main injury pathophysiology is an imbalance between bone microdamage formation and its removal and replacement. A detailed medical history and clinical examination are important for diagnosis, with magnetic resonance imaging representing the gold standard for radiographic confirmation. Treatment and return-to-sport decisions should be individualized and based on injury location, severity, aspects of sports participation, and patient preferences. Initial management includes activity modification, protected weight-bearing, immobilization, optimizing nutrition (caloric intake, dietary calcium, and vitamin D supplementation), and in a few cases surgery. Following initial treatment, progressive loading and return-to-activity are initiated. Overall, a high rate of return-to-sports can be expected. Numerous risk factors that alter bone loading or bone health have been described and their identification is a crucial step towards prevention of future injury.

Clinical Rationale and Rehabilitation Guidelines for Post Biologic Therapy.

The use of orthobiologic modalities such as platelet-rich plasma in orthopedics and sports medicine to deliver high concentrations of naturally occurring biologically active growth factors and proteins to the site of injury is very promising and continues to evolve. Early protection and tissue-specific progressive loading are critical components to successful outcomes following orthobiologic intervention. Each tissue heals and responds differently. Ligament, tendon, muscle, and articular cartilage each have unique healing properties that require tissue-specific loading. The authors have found using a criteria-based loading and exercise progression guided by dynamic imaging when appropriate to further advance the goal-oriented rehabilitation program. Each patient and injured tissue are unique and require specific intervention and rehabilitation.

A Diagnostic Method Based on Deflection Analysis for Monitoring Post-elastic Response of Beams

A non-destructive diagnostic method based on deflection analysis for monitoring the post-elastic response of beams was developed, and a diagnostic indicator was proposed. The indicator was defined as the second moment of the normalised curvature function about the mid-span, where the curvature was computed from the normalised deflection function. Elastic reference values of the indicator were computed for simply supported beams under uniformly distributed load, three-point, and four-point bending. Development of the indicator under progressive loading was examined with the help of finite element analyses. The indicator value monotonically decreased with increasing deformation provided that maximum bending moment was located between 0.41L and 0.59L, where L is the span of the beam. In this interval, the value of the indicator was unique and enabled the direct monitoring of the post-elastic stress level in the cross-section. The method was validated with the help of available experiments on simply supported beams. For beams working in the elastic range, a mean error of {2.1}{%} was obtained between the measured and theoretical indicator values. For quasi-brittle material in the post-elastic stage, the decreasing value of the indicator signified the development of damage in accordance with experimental results.

Effects of Creatine Supplementation after 20 Minutes of Recovery in a Bench Press Exercise Protocol in Moderately Physically Trained Men.

The aims of this study were to analyse the effect of creatine supplementation on the performance improvement in a bench pressing (BP) strength test of muscle failure and to evaluate muscle fatigue and metabolic stress 20 min after the exercise. Fifty young and healthy individuals were randomly assigned to a creatine group (n = 25) or a placebo group (n = 25). Three exercise sessions were carried out, with one week of rest between them. In the first week, a progressive load BP test was performed until the individuals reached the one repetition maximum (1RM) in order to for us obtain the load-to-velocity ratio of each participant. In the second week, the participants conducted a three-set BP exercise protocol against 70% 1RM, where they performed the maximum number of repetitions (MNR) until muscle failure occurred, with two minutes of rest between the sets. After one week, and following a supplementation period of 7 days, where half of the participants consumed 0.3 g·kg-1·day-1 of creatine monohydrate (CR) and the other half consumed 0.3 g·kg-1·day-1 of placebo (PLA, maltodextrin), the protocol from the second week was repeated. After each set, and up to 20 min after finishing the exercise, the blood lactate concentrations and mean propulsive velocity (MPV) at 1 m·s-1 were measured. The CR group performed a significantly higher number of repetitions in Set 1 (CR = 14.8 repetitions, PLA = 13.6 repetitions, p = 0.006) and Set 2 (CR = 8 repetitions, PLA = 6.7 repetitions, p = 0.006) after supplementation, whereas no significant differences were seen in Set 3 (CR = 5.3 repetitions, PLA = 4.7 repetitions, p = 0.176). However, there was a significant increase in blood lactate at minute 10 (p = 0.003), minute 15 (p = 0.020), and minute 20 (p = 0.015) after the exercise in the post-supplementation period. Similarly, a significant increase was observed in the MPV at 1 m·s-1 in the CR group with respect to the PLA group at 10, 15, and 20 min after the exercise. Although the creatine supplementation improved the performance in the strength test of muscle failure, the metabolic stress and muscle fatigue values were greater during the 20 min of recovery.

Role of resistance training in bone macro and micro damages in an estrogen absence animal model

AimsWe evaluated the effects of resistance training (RT) on bone properties, morphology, and bone extracellular matrix (ECM) remodeling markers in an ovariectomy (OVX) rat model. Main methodsThirty-six female rats were divided into four groups: sham sedentary, OVX sedentary, sham RT, and OVX RT. Rats performed RT for ten weeks, during which they climbed a ladder with progressive loads attached to the tail. Tibias were stored for dual-energy X-ray densitometry (DXA), micro-computed tomography (micro-CT), and biomechanical, biophysical, and biochemical analysis. Femurs were stored for morphological, gene expression, and gelatin zymography analysis. Key findingsOVX decreased bone mineral density, stiffness, maximal load, and calcium content, which was reversed by RT. The trabecular number, connectivity, and MMP-13 gene expression decreased in OVX groups. Furthermore, OVX increased run-related transcription factor-2 (RUNX-2) and osteoprotegerin (OPG) gene expression, and increased the number of adipocytes in bone marrow and MMP-2 activity. SignificanceRT was efficient in preventing or reversing changes in bone biomechanical properties in OVX groups, improving fracture load and resilience, which is relevant to prevent fractures. On the other hand, RT did not decrease the number of bone adipocytes in the OVX-RT group. However, RT was efficient for increasing trabecular thickness and cortical bone volume, which improved bone resistance. Our findings provide further insights into the mechanisms involved in the role of RT in OVX damage protection.

TREINAMENTO POR ELEVAÇÃO PROGRESSIVA DE CARGA EM JOVENS JOGADORES DE FUTEBOL

ABSTRACT Introduction: Among the main characteristics of soccer are a long-time of competition and its intensity; its athletes quickly alternate between attack and defense, executing distinct intensities of exercise and manding a high level of physical conditioning. Objective: Verify the impacts of training with progressive load elevation on young soccer athletes. Methods: Fifty students from the soccer special class 2019 of the School of Physical Education were selected as volunteers for the experiment. They were randomly divided into the experimental and control group. The experimental group received a physical training program with progressive load lifting, while the control group received a conventional training program. The experiment lasted 45 minutes daily, three times a week for ten weeks. The fitness index was checked before and after the experiment, and the data were statistically analyzed to verify the influence of the special progressive load lifting training on the physical training of young soccer players and the feasibility of its application in physical training. results: The index scores of the vertical jump and 30m fast run tests were slightly higher than those of the control group (P>0.05). The mean scores of the experimental and control groups were 15.02 and 15.56, and the standard deviations were 1.07 and 0.93, respectively. Conclusion: The experiment's performance in tests of speed, strength, agility, and endurance showed improvements in varying degrees. Among them, the indicators of endurance and sensitivity showed significant differences, indicating that physical training by progressive load elevation can effectively promote the development of endurance and agility in young soccer players. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

EFEITOS DO TREINAMENTO COM CARGAS PROGRESSIVAS NA RESISTÊNCIA CARDIORRESPIRATÓRIA DE VELOCISTAS

ABSTRACT Introduction: The most evident change during exercise is the increase in oxygen demand, and prolonged high-intensity exercises may impact this even more on this demand. Physical training with progressive loads is a method that aims to reach the training goals by adjusting factors such as initial load, stage load, and a load of the athletes and can be a monitor of the aerobic and anaerobic exercise on the athlete with potential benefits for the high demand of oxygenation. Objective: Study the changes in heart rate and indexes of cardiorespiratory endurance of sprinters under training with progressive loads. Methods: By random sampling, the study subjects were 15 male sprinters and 15 non-sportsmen as research volunteers. The study subjects performed a protocol with progressive load training on a platform. All subjects underwent the Italian Kosmai cardiopulmonary function test before and after training. Results: The subjects who did not practice the sport showed VO2 max values at an exercise intensity of 13 km/h. The VO2 max maximum for sprinters was 15 km/h. Individuals who were not sprinters generally showed lower VT levels than sprinters (P <0.05). Average non-speeder individuals demonstrated higher MET scores than sprinters. Conclusion: Cardiopulmonary endurance and energy metabolism levels are strongly related to long-term participation in physical activity and exercise intensity. Incremental load training improved cardiorespiratory fitness in sprinters. The results may provide a specific theoretical basis for the daily training of sprinters in the future. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESULTADOS DA PLIOMETRIA SOBRE A FUNÇÃO MOTORA NOS MEMBROS INFERIORES DE FUTEBOLISTAS

ABSTRACT Introduction: Soccer is watched by hundreds of millions of fans worldwide, in more than 1.5 million teams and 300,000 clubs worldwide, by men and women, children and adults of all levels of expertise. Demanding high performance from its practitioners, achieved only with the strong scientific basis of its technicians by constantly updated research. Objective: Study the results of extensor strength training with plyometrics exercises on the motor function of soccer players' lower limbs. Methods: An experiment with 30 soccer players as research volunteers was performed by randomly dividing them into high load plyometric training group (PHL, 20% of body weight), low load plyometric training group (PLL, 10% of body weight), and control group (CON) for various physiological tests before and after training. Results: Lower limb muscle mass in the PHL group increased significantly; creatine kinase (CK) changes were not statistically significant; regarding isokinetic muscle strength performance, the PHL group showed a significant improvement in peak torque at 60°/s and 180°/s, while the PLL group obtained only a significant improvement at 180°/s. Conclusion: Plyometric exercise promoted a significant improvement in isokinetic muscle strength of the lower extremity of soccer players; its training with different weights did not cause muscle damage. A progressive training load is recommended for athletes with low muscle strength during the initial training phase. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Analysis of velocity- and power-load relationships of the free-weight back-squat and hexagonal bar deadlift exercises

The aim of this study was to analyse the load-velocity and load-power relationships in the free-weight back-squat (BSQ) and hexagonal bar deadlift (HBD) exercises. Twenty-five (n = 25) resistance-trained men (age = 23.7 ± 2.8 years) performed a progressive load test at maximal intended velocity to determine their BSQ and HBD one-repetition maximum (1RM). Mean propulsive velocity (MPV) during the concentric phase of the lift was recorded through a linear encoder. Load-velocity and load-power relationships were analysed by fitting linear regression and the second-order polynomial, respectively, to the data. Maximum strength (1RM), MPV (30-80% 1RM), and power output (30-90% 1RM) were higher for HBD compared to BSQ exercise (p < 0.05). A very strong relationship between MPV and relative intensity was found for both BSQ (R2 = 0.963) and HBD (R2 = 0.967) exercises. The load that maximizes power output (Pmax) was 64.6 ± 2.9% (BSQ) and 59.6 ± 1.1% (HBD) 1RM. There was a range of loads at which power output was not different than Pmax (BSQ: 40-80% 1RM; HBD: 50-70% 1RM). In conclusion, the load-velocity and load-power relationships might assist strength and conditioning coaches to monitor and prescribe exercise intensity in the BSQ and HBD exercises using the velocity-based training approach.

Evolução do dano e da plasticidade em vigas de concreto armado utilizando elementos finitos de vigas de Euler-Bernoulli laminados

abstract: This paper analyses the behaviour of reinforced concrete beams subjected to progressive loads. Although this topic is addressed in recent works through tri-dimensional finite elements, the present study adopts a simpler alternative, using Euler-Bernoulli’s beam finite element. The evolution of the generalized cracking is addressed by Damage Mechanics theory, and the nonlinear constitutive models of concrete and steel are considered, including plasticity and post-peak ‘. The laminated approach permits not only to ascertain the damage evolution but, in practical aspects, makes easy to define vertically symmetrical transversal sections and to distribute the reinforcement as desired, even if the steel rebars have different lengths. It is highlighted the changing of the neutral axis during the damage evolution process, which is updated automatically by the developed numeric-computational code. To validate the proposed methodology, two examples are detailed, both based on experimental tests found in the literature. The results obtained are close to the experimental ones and confirm the applicability of the proposed approach.

Comparative photoelastic stress analysis between all-on-four implant-supported cobalt-chromium framework and carbon fiber reinforced framework with varying cantilever lengths - An in vitro study

CONTEXT: In implant prosthodontics, metal frameworks are used to rigidly spilt the implants together to provide rigidity and stiffness to the prosthesis. However, due to the limitations associated with the metal framework fabrication, the recent advances have made it possible to fabricate metal-free implant-supported prostheses using fiber-reinforced composite frameworks.AIM: This study aimed to evaluate and compare photoelastic stresses between all-on-four implant-supported cobalt-chromium (Co-Cr) framework and the carbon fiber-reinforced composite (CFRC) framework at varying cantilever lengths.MATERIALS AND METHODS: Two photoelastic models of an edentulous mandible were fabricated according to the all-on-four concept. Following this, frameworks with a bilateral cantilever extension of 20 mm, one with CFRC and the other with Co-Cr, were fabricated and were subjected to a progressive load of 120–180 N with an interval of 20 N. The principal stresses (σ) were calculated using the mean maximum fringe order.STATISTICAL ANALYSIS: The quantitative analysis was performed using the Kruskal–Wallis test and Mann–Whitney U-test, P ≤ 0.05.RESULTS: The CFRC framework showed mean principal stress values significantly lower than the Co-Cr framework under all loading conditions; however, deformation of the framework was observed at the cantilever lengths of 15 mm and 20 mm.CONCLUSION: The study and its findings have indicated that the CFRC framework appears suitable for the fabrication of a framework for an “All-on-four” prosthesis. Within the confines of this study, the use of 10 mm as an arbitrary cantilever length recommendation for the CFRC framework and 15 mm for the Co-Cr framework seems reasonable.

Superior bone fixation of conical compared with hemispherical trapezial cup design: an experimental radiostereometry study

PurposeThe most used cup designs for trapeziometacarpal (TMC) arthroplasty are of hemispherical and conical geometrical shape. Using a validated pig bone model, we compared the bone fixation using radiostereometry (RSA).MethodsTwenty saddle-shaped pig forefoot bones were prepared with insertion of bone markers and reaming. Hemispherical Type T cups (Beznoska, Kladno, Czech Republic) (N = 10) and conical Moovis cups (Stryker, Pusignan, France) (N = 10) of 9-mm diameter were inserted press-fit. The bones were fixed in cement blocks for stability, and the cups were loaded in a motorized test stand. First, a low-pressure cyclic load test (0—150N) with 130 compression cycles was performed. Next, a push-in test of progressive loads with 50N increments (range: 150–900N) was applied until a visual change in cup position appeared. Cup migration was evaluated with RSA after every new load application. Cup failure was defined as total translation > 0.5 mm between two load applications.ResultsBoth cup types tolerated a compression load of 450 N without failure. Beyond this load level, the total translation cup migration of mean 0.20 mm (95% CI 0.11; 0.30) for the Type T group was higher than mean 0.10 mm (95% CI 0.06; 0.15) of the Moovis group (p = 0.046). The Hazard ratio for failure was 0.52 (95% CI 0.12; 2.17) (p = 0.37), indicating that the risk of failure was two-fold higher in the Type T group.ConclusionWe conclude that conical TMC cups have superior fixation as compared to hemispherical cups above a loading level of 450 N, which correspond to a 3.8 kg tip-pinch.In a clinical perspective, based on the fixation strength of both cup types, it seems safe to allow light-load activities of daily living such as buttoning a shirt and using a key shortly after surgery and until sufficient osseointegration is achieved.

The load-velocity relationship in the jump squat exercise.

The purpose of this study was to test the load-velocity relationship in the jump squat (JS) exercise using three different velocity parameters (mean velocity [MV], mean propulsive velocity [MPV], and peak velocity [PV]). Twenty-six male rugby union players (24.3 ± 3.9 years; 1.81 ± 0.09 m; 101.3 ± 15.4 kg) performed a progressive loading test in the JS with loads corresponding to 20, 40, 60, and 80% of the half-squat 1RM (equivalent to 24, 46, 70, and 94% of the estimated JS-1RM). MV, MPV, and PV were continuously recorded during all attempts using a linear velocity transducer. Linear regression models were used to determine the relationships between JS loads and MV, MPV, and PV. Bar-velocity outputs demonstrated high levels of consistency and reliability (coefficient of variation ≤ 5% and intraclass correlation coefficient ≥ 0.90). The predictive power of MV, MPV, and PV were ≥ 91%, for all tested variables (P < 0.0001). The equations and bar-velocity values provided in this study can be used by coaches to precisely determine and prescribe JS training loads, from verylight to heavy loading conditions (i.e., ~20-100% JS 1RM).

Blood Flow Restriction Training for Tendinopathy Rehabilitation: A Potential Alternative to Traditional Heavy-Load Resistance Training

Tendinopathy is a chronic tendon disease which can cause significant pain and functional limitations for individuals, and which collectively places a tremendous burden on society. Resistance training has long been considered the treatment of choice in the rehabilitation of chronic tendinopathies, with both eccentric and heavy slow resistance training demonstrating positive clinical effects. The application of progressive tendon loads during rehabilitation is essential to not compromise tendon healing, with the precise dosage parameters of resistance training and external loading a critical consideration. Blood-flow restriction training (BFRT) has become an increasingly popular method of resistance training in recent years and has been shown to be an effective method for enhancing muscle strength and hypertrophy in healthy populations and in musculoskeletal rehabilitation. Traditional resistance training for tendinopathy requires the application of heavy training loads, whereas BFRT utilises significantly lower loads and training intensities, which may be more appropriate for certain clinical populations. Despite evidence confirming the positive muscular adaptations derived from BFRT and the clinical benefits found for other musculoskeletal conditions, BFRT has received a dearth of attention in tendon rehabilitation. Therefore, the purpose of this narrative review was threefold: firstly, to give an overview and analysis of the mechanisms and outcomes of BFRT in both healthy populations and in musculoskeletal rehabilitation. Secondly, to give an overview of the evidence to date on the effects of BFRT on healthy tendon properties and clinical outcomes when applied to tendon pathology. Finally, a discussion on the clinical utility of BFRT and its potential applications within tendinopathy rehabilitation, including as a compliment to traditional heavy-load training, is presented.

Interfacial stress transfer in monolayer and few-layer MoS2 nanosheets in model nanocomposites

Understanding the stress transfer mechanisms from a polymer matrix to two-dimensional (2D) reinforcements is essential for the preparation of high performance nanocomposites. In this study, the interfacial stress transfer from a flexible polymer substrate to monolayer and few-layer molybdenum disulfide (MoS2) under tension has been investigated. Layer-dependent and strain-dependent photoluminescence (PL) spectroscopy were used to examine the stress transfer efficiency. The interlayer stress transfer efficiency of MoS2 was determined to be in the range of 0.76–0.86, higher than that of graphene. The transfer of strain from the polymer substrate to the flakes was derived through strain-dependent band shifts. With progressive loading, the strain distribution in monolayer MoS2 can be described by the shear-lag, partial-debonding and total-debonding models. The interfacial shear and frictional stresses were calculated to quantify the strength of the MoS2/polymer interface. It was found that the strength of the interface is similar to the strength of a graphene-polymer interface. Strain mapping was performed at different strain levels and it was found that the strain distribution in bilayer MoS2 is similar to the case of a monolayer sample. The interfacial shear strength remains almost unaffected, while the stress transfer length increases with increasing layer number.

Excimer Laser coronary atherectomy as adjunctive treatment of severe stent underexpansion with bulky calcification

Excimer Laser coronary atherectomy has improved significantly in recent years, emitting high-energy ultraviolet and short wavelength with less penetration and heat emission, ultimately leading to less tissue damage and fewer complications. We described a case of a 66-year-old male patient, former smoker and suffering from hypertension, diabetes mellitus, and dyslipidemia. He underwent multiple percutaneous coronary interventions in the left anterior descending artery with bare metal and drug-eluting stents. In the last percutaneous coronary intervention, the stent was underexpanded and the patient presented acute stent thrombosis and recurrent stent restenosis. New percutaneous coronary interventions with adjunctive Excimer Laser coronary atherectomy were undertaken due to refractory angina, using progressive load and saline injection, followed by subsequent high-pressure balloon inflation and drug-eluting stent implantation with an excellent result. At 8-month follow-up, the patient was asymptomatic.

Mechanical Performance of AlCrSiN and AlTiSiN Coatings on Inconel and Steel Substrates after Thermal Treatments

The objective of this study was to explore the mechanical properties of AlCrSiN and AlTiSiN coatings deposited on Inconel and steel substrates after thermal treatments of 500 °C and 800 °C. Nanoindentation was used to measure the hardness and elastic modulus of the coatings, and microindentation was used for observing the contact damage with Hertzian contact loadings. Microscratch and Mercedes tests were used to evaluate the adhesive strength between coating and substrate with both progressive and static loads, respectively. The surface damage was inspected by optical microscopy and scanning electron microscopy (SEM). Focus ion beams (FIB) were used to mill the cross-sections in order to detect the extent and mode of failure. The results show that AlCrSiN coatings and Inconel substrates exhibit better mechanical performance, even after thermal treatments.

Development of Ni-B electroless coating from stabilizer free bath and characterization of high temperature tribological behaviour, scratch and corrosion resistance

The current work investigates the effects of variation of coating bath temperature on friction and wear behaviour of electroless Ni–B (ENB) coatings developed from stabilizer free bath. Coating is applied to specimens made up of AISI 1040 steel. Coatings were deposited at three different coating bath temperatures (85 °C, 90 °C and 95 °C). Field emission scanning electron microscopy, inductively coupled plasma-optical emission spectrometer, and x-ray diffraction were used to characterize the coating for surface morphology, chemical composition, and phase structure respectively. Pin-on-disc tribo-tester was used to estimate the friction and wear behaviour of ENB coatings at room temperature (25 °C), 100 °C, 200 °C and 300 °C. The coefficient of friction was higher at high temperature due to higher roughness of the coatings obtained from stabilizer free bath, adhesion and ploughing. The wear rate at 200 °C or 300 °C was lower compared to 100 °C. Additionally, the ENB coatings were subjected to thermogravimetric analysis which reveals higher thermal stability of coatings obtained at 95 °C. A scratch tester at constant (6 N) and progressive load (5–24 N) was used to estimate the coatings scratch hardness and adhesion. The corrosion behaviour of ENB coatings in 3.5% NaCl was studied using potentiodynamic polarization tests. The Ni-B coated specimens could efficiently provide barrier protection to steel substrate. But the corrosion potential was lower compared to lead stabilized bath.